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100 Rarest Things in The Universe _ Fall Asleep To Astrology · Abide Meditation App

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Speaker 1: Hello there, and welcome to the Sleepy Science Channel. Tonight,
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Speaker 1: we'll be exploring some of the rarest things ever discovered
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Speaker 1: in the universe. Space is unimaginably large, yet some objects
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Speaker 1: and events remain astonishingly uncommon. A few exist only for
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Speaker 1: a brief stage in cosmic history. Others are so difficult
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Speaker 1: to create that astronomers have found only a handful of examples.
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Speaker 1: Some stars spend just moments of their enormous lifetimes in
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Speaker 1: their rarest forms. Certain planets survive in places where worlds
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Speaker 1: seem unlikely to exist at all. There are also particles
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Speaker 1: that can cross immense distances before they interact with anything.
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Speaker 1: Rarity in the universe is not always about being small
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Speaker 1: or hidden. Sometimes it comes from an extraordinary chain of
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Speaker 1: events that must happen in exactly the right way. Tonight,
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Speaker 1: we'll explore what makes these cosmic exceptions so unusual. We'll
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Speaker 1: also discover why finding even one of them can change
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Speaker 1: what scientists understand about the universe. If you enjoy these
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Speaker 1: gentle journeys, I invite you to like, subscribe, or share
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Speaker 1: a thought below. It helps others find their way here too,
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Speaker 1: one sleepy soul at a time, But for Now, all
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Speaker 1: you need to do is get settled in. Let your
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Speaker 1: shoulders soften, let your breathing slow, and allow your mind
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Speaker 1: to settle into stillness as we embark on this fascinating
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Speaker 1: journey together. Let's begin. Only one known planet has ever
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Speaker 1: produced intelligent life. Earth is the only world where we
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Speaker 1: know matter has organized itself into beings capable of building
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Speaker 1: technology and studying the cosmos. That does not mean intelligent
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Speaker 1: life exists nowhere else. It means every cane found example
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Speaker 1: we possess comes from this single planet. Astronomers have discovered
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Speaker 1: thousands of worlds beyond the Solar System, including rocky planets
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Speaker 1: and worlds orbiting within regions where liquid water could potentially exist,
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Speaker 1: yet none has produced a confirmed biological signal. The search
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Speaker 1: becomes even harder when intelligence enters the picture. A technological
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Speaker 1: civilization might reveal itself through artificial radio transmissions or unusual
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Speaker 1: atmospheric chemicals produced by industry. Scientists call such clues techno signatures.
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Speaker 1: Searchers have listened to nearby stars and examined distant pernatory systems,
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Speaker 1: but nothing has yet crossed the threshold into confirmed extraterrestrial technology.
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Speaker 1: That leaves Earth in an extraordinary position across everything humanity
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Speaker 1: has observed. So far, one small world remains the only
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Speaker 1: place known to have produced creatures capable of asking whether
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Speaker 1: anyone else is out there. The rarest stars can outshine
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Speaker 1: entire galaxies before vanishing forever for most of its existence.
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Speaker 1: Even a massive star shines with remarkable stability. Then a
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Speaker 1: very small number end their lives with an eruption so
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Speaker 1: bright that the individual stellar death becomes more luminous than
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Speaker 1: billions of ordinary stars around it. These events are called
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Speaker 1: superluminous super and ova. They can produce at least ten
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Speaker 1: times more visible light than a typical cor collapse super
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Speaker 1: and ova for a short period, one exposion can dominate
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Speaker 1: the galaxy containing it. The star itself does not survive
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Speaker 1: in its original form. Its center collapses while its outer
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Speaker 1: layers race into space. One possible engine behind the extraordinary
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Speaker 1: brightness is a newborn magnetar. This is a rapidly spinning
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Speaker 1: neutron star with an immense magnetic field. As the magnetar
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Speaker 1: loses rotational energy, that energy can pour into the expanding
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Speaker 1: debris and keep it shining far longer than a normal explosion.
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Speaker 1: Astronomers have identified only a few hundred exceptional core collapse
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Speaker 1: events of this general superluminous class, making every new detection
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Speaker 1: of valuable glimpse of an unusually violent stellar ending. Some
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Speaker 1: black holes may have formed before the first stars existed.
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Speaker 1: These hypothetical objects are known as primordial black holes, are
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Speaker 1: my ordinary black holes. They would not have begun with
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Speaker 1: the collapse of dying stars. Instead, they could have formed
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Speaker 1: from unusually dense patches of matter during the universe's earliest moments.
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Speaker 1: Conditions then were completely unlike anything that exists today. Matter
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Speaker 1: and radiation were packed together at extreme temperatures while the
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Speaker 1: universe expanded rapid. If one region became dense enough, gravity
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Speaker 1: might have overwhelmed the expansion locally and crushed that region
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Speaker 1: into a black hole. The resulting objects could have formed
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Speaker 1: with an enormous range of masses, depending on the exact
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Speaker 1: mechanism involved. None has been confirmed. Scientists continue searching because
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Speaker 1: primordial black holes could help answer major questions about cosmology.
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Speaker 1: Some models allow them to contribute to the mysterious dark
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Speaker 1: matter that outweighs ordinary matter throughout galaxies. Discovering even one
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Speaker 1: would be astonishing. It would mean nature found a way
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Speaker 1: to manufacture black holes before stars had appeared to provide
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Speaker 1: the usual route to their creation. Neutron star collisions create
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Speaker 1: much of the universe's gold and platinum. Gold can begin
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Speaker 1: with two dead stars spiraling toward destruction. Neutron stars contain
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Speaker 1: matter crushed to extraordinary densities. When two of them orbit
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Speaker 1: each other, they gradually lose energy through gravitational waves until
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Speaker 1: they finally collide. The merger throws neutron rich material into
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Speaker 1: space at tremendous speeds. Inside that debris, atomic nuclei can
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Speaker 1: capture neutrons with extraordinary rapidity. This process builds some of
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Speaker 1: the heaviest elements found in nature. The radioactive material then
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Speaker 1: powers a rapidly changing glow called achilanova. In two thousand seventeen,
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Speaker 1: astronomers witnessed one after detecting gravitational waves from the merger
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Speaker 1: known as g W one seven zero eight one seven.
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Speaker 1: Telescopes followed the fading light and found evidence consistent with
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Speaker 1: the production of heavy nuclei through this rapid neutron capture process.
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Speaker 1: The event provided direct observational support for neutron style mergers
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Speaker 1: as an important source of precious heavy elements. Other explosive
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Speaker 1: environments may contribute as well. Still, some of the gold
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Speaker 1: now resting quiety on Earth may owe its existence to
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Speaker 1: collisions between stellar remnants that occurred long before how Solar
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Speaker 1: System formed. A few planets orbit the burned remains of
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Speaker 1: dead stars. The first confirmed planets discovered beyond our Solar
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Speaker 1: System were not found around a normal star. They were
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Speaker 1: found around a pulsar. A pulsar is the rapidly spinning
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Speaker 1: remnant left when a massive star collapses and explodes. It
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Speaker 1: packs more mass than the Sun can contain into a
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Speaker 1: sphere only about the size of a city. Its rotating
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Speaker 1: magnetic field produces beams of radiation that sweep across space
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Speaker 1: with remarkable regularity. Tiny changes in that timing revealed planets
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Speaker 1: orbiting the pulsar p s r B twelve fifty seven
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Speaker 1: plus twelve. Their existence was astonishing because the system had
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Speaker 1: already passed through a Stella catastrophe. The original planets may
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Speaker 1: have been destroyed during the supernova. If so, the worlds
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Speaker 1: now present could represent a second generation assembled from debris
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Speaker 1: around the neutron star. Another possibility is that some materials
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Speaker 1: survived and later reorganized. Either way, pulsar planets proved a
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Speaker 1: planet formation is not restricted to calm young stars. Worlds
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Speaker 1: can appear around stellar remains after an environment has undergone
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Speaker 1: one of nature's most violent transformations. The universe contains enormous
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Speaker 1: regions with almost no galaxies inside them. Maps of the
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Speaker 1: cosmos reveal that galaxies do not fill space evenly. They
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Speaker 1: gather along enormous structures that surround immense regions containing remarkably
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Speaker 1: little visible matter. These underpopulated regions are called cosmic voids.
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Speaker 1: Some stretch for hundreds of millions of light years. They
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Speaker 1: are not perfectly empty. Faint galaxies and thin traces of
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Speaker 1: matter can still exist inside them. What makes avoid extraordinary
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Speaker 1: is how little it contains compared with the crowded filaments
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Speaker 1: around it. Gravity helped create this pattern slight differences in
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Speaker 1: density existed in the early universe. Denser regions attracted more
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Speaker 1: matter as cosmic history unfolded, while under dense regions lost
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Speaker 1: material to their surroundings and became increasingly empty. The result
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Speaker 1: is the vast structure astronomers observe today. Voids are scientifically
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Speaker 1: valuable because their shapes preserve information about how the universe expanded.
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Speaker 1: Future surveys can measure thousands of them with increasing precision.
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Speaker 1: Something that appears to contain almost nothing can therefore become
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Speaker 1: a powerful laboratory for understand dark energy and the large
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Speaker 1: scale evolution of the cosmos. Some stars are so ancient
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Speaker 1: they formed near the cosmic dawn. A few surviving stars
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Speaker 1: were born when the universe contained almost none of the
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Speaker 1: heavier elements common today. One remarkable example is SMSs J
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Speaker 1: zero three one three minus six seven zero eight. Its
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Speaker 1: chemical composition contains extraordinarily little iron. That matters because elements
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Speaker 1: such as iron had to be manufactured inside earlier generations
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Speaker 1: of stars. A star with almost none can therefore preserve
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Speaker 1: conditions from a much younger universe. Researchers estimate that this
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Speaker 1: ancient object formed only a few hundred million years after
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Speaker 1: the Big Pain. It still survives because it began with
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Speaker 1: a sufficiently low mass to burn its nuclear fuel slowly.
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Speaker 1: Its atmosphere acts almost like archaeological evidence. The pattern of
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Speaker 1: carbon and other elements suggests that the gas from which
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Speaker 1: it formed may have been enriched by one of the
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Speaker 1: first stellar explosions. Those vanished early stars cannot be observed
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Speaker 1: directly today, yet their chemical fingerprints remain inside survivors studying
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Speaker 1: an ancient star can therefore reveal something about stars that
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Speaker 1: lived and died more than thirteen billion years ago. Rare
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Speaker 1: galaxies appear to contain almost no visible dark matter. Dark
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Speaker 1: matter is normally thought to provide the hidden gravitational framework
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Speaker 1: around which galaxies form. That is why NNGCI two DF
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Speaker 1: two caused such surprise when measurements suggested it contained far
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Speaker 1: less dark matter than astronomers expected. Another diffuse galaxy in
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Speaker 1: the same general environment showed a similarly puzzling shortage. These
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Speaker 1: objects are extremely faint and spread their stars across large areas.
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Speaker 1: Determining their masses requires measuring how stars or compact star
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Speaker 1: clusters move inside them. The interpretation has generated debate because
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Speaker 1: distance measurements and assumptions about the systems can strongly affect
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Speaker 1: the result. For LNGC ten fifty two D four, deep
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Speaker 1: observations revealed evidence that a neighboring galaxy is gravitationally stripping
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Speaker 1: material away. Dark matter extends farther from a galaxy center
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Speaker 1: than most of its stars, so it can be removed
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Speaker 1: first during such an encounter. That offers one possible explanation
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Speaker 1: for how a galaxy could lose much of its invisible
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Speaker 1: mass while still retaining a visible stellar core. These unusual
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Speaker 1: systems turn dark matter itself into something astronomers can investigate
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Speaker 1: by noticing where it seems to be missing. Certain cosmic
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Speaker 1: explosions release more energy than our sun, ever will Gamma
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Speaker 1: ray bursts rank among the most powerful explosions known. They
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Speaker 1: arrive as sudden flashes of extremely energetic radiation from distant
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Speaker 1: regions of the universe. Some last less than a second,
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Speaker 1: Others continue for many seconds before fading into an after
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Speaker 1: glow that telescopes can follow across several wavelengths. The longer
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Speaker 1: variety is often associated with the collapse of massive stars.
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Speaker 1: During the catastrophe, material falls toward a newly formed compact object.
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Speaker 1: While narrow jets can blast outward at speeds close to
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Speaker 1: that of light. If one jet points toward Earth, the
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Speaker 1: event appears astonishingly bright. In only seconds, a powerful burst
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Speaker 1: can release an amount of energy comparable to what the
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Speaker 1: Sun radiates across its entire lifetime. This does not mean
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Speaker 1: the explosion shines equally in every direction, because much of
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Speaker 1: the output can be concentrated into narrow beams, the scale
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Speaker 1: is still extraordinary. A star that existed for millions of years,
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Speaker 1: can reach its final moments and suddenly produce one of
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Speaker 1: the brightest detectable events across the observable universe. Some of
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Speaker 1: the rarest detected high energy cosmic neutrinos cross galaxies. Almost
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Speaker 1: untouched neutrinos interact with ordinary matters so reluctantly that enormous
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Speaker 1: numbers can pass through planets without striking a single atom.
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Speaker 1: High energy cosmic neutrinos are particularly valuable because their extreme
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Speaker 1: energies point toward violent astrophysical environments. They can travel directly
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Speaker 1: from regions that visible light may struggle to escape. That
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Speaker 1: makes them unusual cosmic messengers. The Ice Cube Neutrino Observatory
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Speaker 1: searches for them, using more than a cubic kilometer of
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Speaker 1: Antarctic ice. Mostris use pass straight through the detector. Very occasionally,
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Speaker 1: one interacts with matter near the buried sensors and produces
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Speaker 1: charged particles whose faint light can be measured. Those rare
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Speaker 1: detections can reveal where the incoming neutrino originated ice cube
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Speaker 1: has link high energy neutrino emission with active galaxies containing
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Speaker 1: feeding supermassive black holes. Because neutrinos carry no electric charge.
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Speaker 1: Magnetic fields do not bend their paths as they bend
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Speaker 1: charged cosmic rays. An energetic neutrino can therefore cross immense
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Speaker 1: into galactic distances while preserving a directional clue to the
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Speaker 1: extreme event that launched it. Catching one is like intercepting
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Speaker 1: a messenger designed to pass almost invisibly through the universe.
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Speaker 1: Magnetarles possess the strongest confirmed magnetic fields in the universe.
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Speaker 1: A magnetar begins as the collapsed core of a massive star,
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Speaker 1: but its magnetic field places it in an extreme class
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Speaker 1: of its own. These neutron stars can possess fields thousands
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Speaker 1: of times stronger than those of ordinary neutron stars. Their
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Speaker 1: magnetic energy can twist the crust until the surface fractures.
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Speaker 1: The resulting disturbance can release intense bursts of X rays
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Speaker 1: and gamma rays. One famous event came from SGR eighteen
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Speaker 1: zero six minus twenty in two thousand four. Although the
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Speaker 1: magnetar was tens of thousands of light years away, its
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Speaker 1: giant flare was powerful enough to affect Earth's upper atmosphere.
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Speaker 1: Magnetars are also remarkably compact. Their stellar mass is packed
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Speaker 1: inside an object roughly comparable in width to a city.
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Speaker 1: Scientists proposed their existence before observations established them as a
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Speaker 1: distinct population of neutron stars. Today, only a small number
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Speaker 1: are confirmed, compared with the enormous number of ordinary stars
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Speaker 1: in the Milky Way. Their combination of compactness and magnetic
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Speaker 1: intensity makes them natural laboratories for physical conditions that cannot
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Speaker 1: be reproduced on Earth. Only a handful of stars are
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Speaker 1: known to contain strange, heavy elements. One of astronomy's most
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Speaker 1: peculiar stellar spectra belongs to Priseebelski's Star. When astronomers separate
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Speaker 1: its light into individual wavelengths, they find an extraordinary chemical
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Speaker 1: pattern unlike that of an ordinary star. Numerous rare elements
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Speaker 1: appear unusually abundant in its atmosphere. Researchers have even reported
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Speaker 1: spectral lines attributed to short lived radioactive actinides. Those identifications
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Speaker 1: are difficult and remain scientifically challenging because stellar spectra can
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Speaker 1: become extremely crowded. The deeper mystery is how such substances
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Speaker 1: could remain detectable in a star where some radioactive isotopes
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Speaker 1: should decay away on much shorter time scales than the
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Speaker 1: star's age. Chemically peculiar stars can concentrate particular elements through
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Speaker 1: processes such as atomic diffusion. Radiation pushes some ions upward,
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Speaker 1: while gravity pulls others deeper into the atmosphere. That can
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Speaker 1: create surface compositions that bear little resemblance to the star
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Speaker 1: as a whole Pushibilsky's star pushes this effect to an
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Speaker 1: extraordinary extreme. Its spectrum has encouraged explanations involving unusual nuclear
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Speaker 1: processes and material deposited from outside. No single explanation has
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Speaker 1: settled every detail, which is exactly why this rare star
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Speaker 1: continues to attract attention. Thorn ZiT Cow jects may hide
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Speaker 1: neutron stars inside swollen giants. Imagine a neutron star entering
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Speaker 1: the extended atmosphere of a much larger companion and spiraling
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Speaker 1: all the way toward its center. The proposed result is
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Speaker 1: a thorned Zitcow object. From the outside, it could resemble
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Speaker 1: an ordinary red supergiant. Deep inside, however, the normal stellar
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Speaker 1: core would be replaced by an incredibly gainst neutron star.
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Speaker 1: Physicists Kip Thorne and Anna Zitcow explored the idea decades ago.
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Speaker 1: Such an object might form during the complicated evolution of
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Speaker 1: a close binary system, Astronomers have searched for chemical clues
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Speaker 1: because unusual nuclear reactions near the embedded neutron star could
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Speaker 1: potentially enrich the outer atmosphere with distinctive elements. The red
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Speaker 1: supergiant h V two one one two was once highlighted
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Speaker 1: as a promising candidate because its spectrum showed intriguing abundance patterns.
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Speaker 1: Conformation has remained elusive. Recent simulations have even questioned whether
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Speaker 1: a neutron star could remain stable in inside the envelope
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Speaker 1: for long enough to create a lasting object. It might
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Speaker 1: instead accrete matter rapidly and collapse into a black hole
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Speaker 1: thorn Zitkow. Objects therefore occupy a fascinating boundary between predicted
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Speaker 1: stellar physics and objects still awaiting decisive observational proof. Some
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Speaker 1: hypervelocity stars are escaping the Milky Way completely. Most stars
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Speaker 1: travel around the galaxy while remaining permanently trapped by its gravity.
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Speaker 1: Hypervelocity stars break that rule. They move so quickly that
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Speaker 1: some have enough speed to escape the Milky Way and
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Speaker 1: continue into intergalactic space. One dramatic way to produce such
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Speaker 1: a runaway begins near the supermassive black hole at the
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Speaker 1: center of our galaxy. If a tightly bound stellar system
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Speaker 1: passes dangerously close, a black hole can capture one member
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Speaker 1: while gravitationally flinging another outward at extraordinary Voluney Hubble observations
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Speaker 1: trace the motion of the star he zero four three
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Speaker 1: seven minus five four thirty nine back toward the galactic center.
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Speaker 1: It was traveling at roughly one and a half million
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Speaker 1: miles per hour When studied, the journey creates a strange
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Speaker 1: stellar destiny. Instead of spending its life orbiting among billions
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Speaker 1: of neighbors, an ejected star can eventually leave the galaxy
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Speaker 1: that formed it. Other mechanisms can also create extreme stellar speeds.
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Speaker 1: Exploding companions and interactions within dense systems may launch additional runaways.
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Speaker 1: These rare stars allow astronomers to study violent gravitational encounters
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Speaker 1: by following the objects those encounters throw away. Blue stragglers
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Speaker 1: appear mysteriously younger than their ancient stellar neighbors. Old star
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Speaker 1: clusters should follow a predictable pattern. Their most massive stars
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Speaker 1: exhaust their fuel first, leaving lower mass stars behind. Yet
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Speaker 1: astronomers repeatedly find unusually blue and luminous stars sitting among
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Speaker 1: populations that should be too old to contain them. These
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Speaker 1: apparent rule breakers are blue stragglers. Their color makes them
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Speaker 1: look younger than neighboring stars that formed at roughly the
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Speaker 1: same time. The secret is not that they were born recently.
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Speaker 1: Many have been rejuvenated. A star can gain fresh material
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Speaker 1: from a binary companion, increasing its mass and changing its appearance.
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Speaker 1: Stellar collisions can also create blue stragglers in crowded environments.
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Speaker 1: Recent observations across dozens of globular clusters have strengthened the
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Speaker 1: case that mass transfer within binary systems is an especially
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Speaker 1: important route. That means an ancient star can effectively alter
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Speaker 1: its evolutionary clock by acquiring additional fuel. Blue stragglers do
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Speaker 1: not truly reverse time. Instead, they reveal how interactions between
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Speaker 1: stars can disrupt the simple life story expected from isolated
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Speaker 1: object in an old cluster. Their unexpected brightness records a
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Speaker 1: hidden history of stellar relationships. A few stars may be
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Speaker 1: powered partly by captured dark matter. No dark matter powered
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Speaker 1: star has been confirmed, but theoretical models allow an extraordinary possibility.
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Speaker 1: In regions where dark matter is unusually concentrated, particles could
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Speaker 1: become gravitationally captured inside a forming star. If those particles
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Speaker 1: can annihilate with one another, their mass would be converted
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Speaker 1: into energy and heat the surrounding gas. This idea gave
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Speaker 1: rise to models known as dark stars. Despite the name,
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Speaker 1: such an object could be extremely luminous. Its unusual power
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Speaker 1: source might delay the normal onset of nuclear fusion and
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Speaker 1: allow the star to grow to enormous mass while remaining
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Speaker 1: relatively cool at its surface. Researchers have suggested that conditions
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Speaker 1: in the early universe may have been particularly suitable because
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Speaker 1: the first structures formed inside dense concentrations of dark matter.
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Speaker 1: Some proposed dark stars could eventually collapse and provide seeds
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Speaker 1: from which early supermassive black holes grow. The entire scenario
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Speaker 1: depends on properties of dark matter that remain unknown. That
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Speaker 1: makes the idea especially intriguing. Finding one would not merely
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Speaker 1: reveal a new kind of star. It could expose how
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Speaker 1: an invisible form of matter behaves at the particle level.
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Speaker 1: Wolf Rayed stars expose their blazing interiors before exploding. Most
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Speaker 1: stars hide the products of nuclear fusion beneath enormous outer envelopes.
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Speaker 1: Wolf rayed stars have lost much of that covering. Powerful
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Speaker 1: stellar winds or interactions with a companion can strip away
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Speaker 1: their hydrogen rich outer material and reveal layers that were
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Speaker 1: once buried deeper inside their spectra can therefore show strong
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Speaker 1: signatures of helium or products associated with later nuclear burning.
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Speaker 1: These stars are extremely hot and luminous. They also shed
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Speaker 1: material at tremendous rates through winds traveling thousands of kilometres
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Speaker 1: per second. Some wolf rayet systems manufacture carbon rich dust
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Speaker 1: when winds from two massive stars collide. The James Webb
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Speaker 1: Space Telescope has watched expanding dust shells around wolf Ray
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Speaker 1: at one forty new shells form as the stars approach
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Speaker 1: one another during their elongated orbit. For many wolf Ried stars,
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Speaker 1: the stripped condition represents a late stage before core collapse.
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Speaker 1: Astronomers study them because their exposed layers are for an
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Speaker 1: unusual opportunity to examine the internal evolution of massive stars
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Speaker 1: before their lives end. Instead of seeing only a stellar surface,
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Speaker 1: we can observe material that once belonged much deeper within
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Speaker 1: the star. Yellow hypergiants occupy one of the briefest stages
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Speaker 1: in stellar evolution. A yellow hypergiant is what can happen
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Speaker 1: when an extremely massive evolved star enters a violently unstable
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Speaker 1: phase of its life. These stars are exceptionally luminous and
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Speaker 1: lose matter at enormous rates. Their rarity comes party from
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Speaker 1: the fact that only very massive stars can become them.
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Speaker 1: It also comes from how rapidly this evolutionary stage can pass.
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Speaker 1: Astronomers therefore have relatively few confirmed examples to examine. In
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Speaker 1: recent years, one remarkable star has offered the chance to
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Speaker 1: watch such a transition unfold. WHG six four in the
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Speaker 1: Large Magellanic Cloud had long been known as an extreme
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Speaker 1: red supergiant. Observations showed that its spectrum changed dramatically as
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Speaker 1: the object became hotter and entered a yellow hypergeant state.
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Speaker 1: Researchers reported evidence that this transformation occurred over an astonishingly
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Speaker 1: short interval by stellar standards. The exact future of such
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Speaker 1: stars remains uncertain. They may continue shedding their outer layers
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Speaker 1: before eventually undergoing core collapse. Catching one in transition is
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Speaker 1: valuable because human astronomy usually sees stellar evolution as isolated
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Speaker 1: snap shots, rather than watching a giant star visibly change
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Speaker 1: its evolutionary identity. Rare carbon stars cloak themselves in soot
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Speaker 1: made from their atmospheres a carbon star can manufacture the
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Speaker 1: material that eventually hides it from view. These evolved stars
27:53
Speaker 1: contain more carbon than oxygen in their outer atmospheres. That
27:58
Speaker 1: chemical imbalance changes which molecules and dust grains can form.
28:02
Speaker 1: As material escapes from the stellar surface, carbon rich compounds
28:07
Speaker 1: condense in the cooling outflow and create tiny solid particles.
28:12
Speaker 1: Over time, those grains can build a dusty envelope around
28:16
Speaker 1: the star. The effect can become so strong that visible
28:19
Speaker 1: light from the stellar surface is heavily obscured, while the
28:23
Speaker 1: surrounding dust glows brightly in infrared wavelengths. The dust does
28:29
Speaker 1: not stay there forever. Stellar winds carry it outward into
28:33
Speaker 1: interstellar space. That makes evolved carbon rich stars important contributors
28:38
Speaker 1: to the raw material available for later generations of stars
28:42
Speaker 1: and planetary systems. Some grains formed around ancient stars have
28:47
Speaker 1: even survived inside primitive Solar system material. Carbon stars therefore
28:53
Speaker 1: do something remarkable near the ends of their lives. They
28:56
Speaker 1: manufacture solid particles from elements forged and rear ranged through
29:00
Speaker 1: stellar evolution, then release those particles into the galaxy, where
29:05
Speaker 1: the same material can participate in entirely new cosmic talinae structures.
29:11
Speaker 1: Some white dwarfs are slowly crystallizing into planet sized cosmic diamonds.
29:17
Speaker 1: A white dwarf is the dense stellar core left behind
29:21
Speaker 1: after a sun like star reaches the end of its
29:23
Speaker 1: active life. It no longer produces energy through ordinary nuclear fusion. Instead,
29:30
Speaker 1: it spends billions of years cooling. Deep inside, matter exists
29:36
Speaker 1: at densities far beyond anything familiar on Earth. As the
29:40
Speaker 1: temperature gradually falls, the carbon and oxygen nuclei can begin
29:44
Speaker 1: arranging themselves into an ordered solid structure. In other words,
29:48
Speaker 1: the interior crystallizes. Astronomers long predicted this transformation, but observations
29:56
Speaker 1: from the Gay emission revealed a clear signature of crystallization
30:00
Speaker 1: across a large population of white dwarfs. The process also
30:04
Speaker 1: releases energy, which temporarily slows the stars cooling and affects
30:09
Speaker 1: estimates of its age. Calling these remnant diamonds is an
30:14
Speaker 1: appealing shorthand because many contain crystallized carbon. Their internal structure
30:20
Speaker 1: is not identical to a jewelry diamond. The scale is
30:25
Speaker 1: far more extraordinary. A stellar remnant roughly comparable to Earth
30:29
Speaker 1: in size, can progressively solidify from the inside outward far
30:34
Speaker 1: in the future, our own sun is expected to become
30:38
Speaker 1: a white dwarf and eventually undergo this same transformation. Pulsars
30:44
Speaker 1: can spin hundreds of times during a single second. Some
30:48
Speaker 1: collapsed stars rotate so quickly that their surfaces move at
30:52
Speaker 1: a significant faction of light speed. The fastest confirmed example
30:56
Speaker 1: spins more than seven hundred times every second. Each rotation
31:01
Speaker 1: sweeps beams of radio energy across space from regions near
31:06
Speaker 1: the magnetic poles. When one beam repeatedly crosses Earth, telescopes
31:11
Speaker 1: detect an astonishingly regular pulse. This is why these objects
31:16
Speaker 1: became known as pulsars. Their timing can rival the stability
31:21
Speaker 1: of atomic clocks over long periods. The speed becomes even
31:25
Speaker 1: more remarkable when you remember what is spinning. A neutron
31:29
Speaker 1: star can contain more mass than the Sun inside a
31:32
Speaker 1: sphere only a few tens of kilometers across. Many rapid
31:37
Speaker 1: pulsars were accelerated by stealing matter from a companion star.
31:42
Speaker 1: Gas spiraling inward, transferred angular momentum, and gradually spun the
31:47
Speaker 1: neutron star faster. Astronomers call this recycling. Eventually, the companion
31:54
Speaker 1: may be stripped down or transformed, while the pulsar remains
31:58
Speaker 1: turning at an extraordinary rate. Somewhere in the galaxy. An
32:02
Speaker 1: object heavier than the Sun can complete hundreds of full
32:05
Speaker 1: rotations before you finish saying its name. At least one
32:10
Speaker 1: pulsar system contains planets that probably formed after stellar catastrophe.
32:17
Speaker 1: The planets around PSRB twelve fifty seven plus twelve forced
32:21
Speaker 1: astronomers to reconsider where worlds can exist. Their host is
32:26
Speaker 1: not a normal star. It is a rapidly rotating neutron
32:31
Speaker 1: star left behind after a massive stellar explosion. Any original
32:36
Speaker 1: planetary system would have faced intense radiation and a violent
32:39
Speaker 1: loss of stellar material. Yet several small worlds now orbit
32:44
Speaker 1: the remnant with remarkable regularity. One leading possibility is that
32:49
Speaker 1: they formed afterward from a disc of debris surrounding the
32:52
Speaker 1: newly created pulsar. Material thrown outward during the explosion or
32:57
Speaker 1: supplied by a former companion could have set into orbit
33:01
Speaker 1: and assembled into planets. Another possibility is that surviving worlds
33:05
Speaker 1: were dramatically altered rather than created from scratch. Their exact
33:10
Speaker 1: history remains debated. What matters is the planet formation clearly
33:15
Speaker 1: found a route through an environment that seemed almost impossible.
33:19
Speaker 1: The discovery also carried historical importance because these were the
33:23
Speaker 1: first confirmed planets found beyond our solar system. Humanity's first
33:28
Speaker 1: proven alien worlds were not circling a sun like star.
33:32
Speaker 1: They were circling the remains of one that had already died.
33:36
Speaker 1: Rotating radio transients flash briefly before disappearing for hours. Some
33:42
Speaker 1: neutron stars refuse to behave like dependable cosmic clocks. Rotating
33:47
Speaker 1: radio transients can remain undetectable through hundreds or thousands of
33:51
Speaker 1: rotations before suddenly producing a short burst of radio waves.
33:56
Speaker 1: Then they vanish again. Their flashes may lie us only milliseconds,
34:01
Speaker 1: while the gaps between detectable bursts can stretch for minutes
34:04
Speaker 1: or even hours. That makes them easy to miss and
34:08
Speaker 1: difficult to study. Astronomers recognize the class after searching old
34:13
Speaker 1: survey data for isolated radio bursts rather than the regular
34:17
Speaker 1: pulse trains expected from conventional pulses. The objects are thought
34:22
Speaker 1: to be rotating neutron stars, but researchers still debate why
34:26
Speaker 1: their emission appears so sporadic. Some may produce radio beams continuously,
34:32
Speaker 1: while our instruments detect only rare, bright pulses. Others may
34:37
Speaker 1: genuinely switch their radio emission on and off. Their slow
34:41
Speaker 1: and irregular appearance opens a hidden population of stellar remnants
34:45
Speaker 1: that ordinary pulsar searchers can overlook. A neutron star could
34:50
Speaker 1: therefore sit inside our own galaxy for ages, while revealing
34:54
Speaker 1: itself to Earth through nothing more than an occasional millisecond flash,
34:58
Speaker 1: separated by long stres apparent silence. A few neutron stars
35:03
Speaker 1: may contain entirely unfamiliar forms of matter. The center of
35:08
Speaker 1: a neutron star reaches densities so extreme that ordinary descriptions
35:13
Speaker 1: of matter begin to break down. Atomic nuclei cannot remain
35:17
Speaker 1: intact there. Deeper still, even matter made mostly from neutrons
35:23
Speaker 1: may transform into something stranger. Physicists have proposed interiors containing hyperons.
35:30
Speaker 1: These are heavy particles that include strange quarks. Other models
35:35
Speaker 1: allow condensates of exotic particles or phases where quarks are
35:39
Speaker 1: no longer confined inside individual protons and neutrons. Some regions
35:44
Speaker 1: may also behave as superfluids that flow with almost no
35:47
Speaker 1: internal resistance. At the same time, charged particles could form
35:52
Speaker 1: superconducting states with unusual magnetic behavior. Nobody can open a
35:57
Speaker 1: neutron star and inspected center diary directly. Instead, astronomers infer
36:03
Speaker 1: the possibilities by measuring masses and radii. They also study
36:08
Speaker 1: cooling rates and gravitational waves from mergers. Each measurement rules
36:14
Speaker 1: out some descriptions while leaving others alive. The puzzle is
36:19
Speaker 1: fundamental because these stellar remnants compress more than a sum's
36:23
Speaker 1: worth of matter into conditions unavailable in laboratories. Their centres
36:29
Speaker 1: may therefore contain phases of nature that have existed for
36:32
Speaker 1: billions of years without ever appearing naturally on Earth. Strange
36:37
Speaker 1: stars could be built from particles unlike ordinary atomic nuclei.
36:42
Speaker 1: There is an even more radical possibility than a neutron
36:45
Speaker 1: star with an exotic core. The entire object might be
36:49
Speaker 1: made largely from strange quark matter. Normal protons and neutrons
36:55
Speaker 1: contain up and down quarks. Under extreme pressure, some theories
37:00
Speaker 1: suggests matter containing strange quarks could become stable as well.
37:05
Speaker 1: If that state were energetically favored. A collapsed stellar remnant
37:09
Speaker 1: might convert much of itself into a dense mixture of
37:12
Speaker 1: freely interacting quarks. The hypothetical result is called a strange star.
37:20
Speaker 1: From a distance, it could resemble an ordinary neutron star.
37:24
Speaker 1: Its mass might be comparable and its diameter could be similar.
37:30
Speaker 1: The differences would hide in the relationship between those properties
37:34
Speaker 1: and in how the object cools or responds to violent events.
37:38
Speaker 1: Astronomers have occasionally proposed strange stars to explain unusual compact objects,
37:44
Speaker 1: but none has been confirmed. The idea remains scientifically serious
37:50
Speaker 1: because the behavior of matter at enormous density is still uncertain.
37:55
Speaker 1: Finding one would reveal that familiar atomic matter is not
37:59
Speaker 1: the only stable way nature can pack large quantities of
38:03
Speaker 1: substance into a stellar sized object. Quark nova remain a
38:07
Speaker 1: possible second explosion after certain supernovas. A dying massive star
38:13
Speaker 1: may not always finish exploding after its first catastrophic collapse.
38:18
Speaker 1: In one speculative scenario, the newly formed neutron star survives
38:23
Speaker 1: for a time before its interior undergoes another profound transformation.
38:28
Speaker 1: If the pressure becomes high enough, ordinary neutron rich matter
38:32
Speaker 1: could convert into deconfined quark matter. That sudden transition might
38:37
Speaker 1: release enough energy to drive a second explosion. Researchers call
38:41
Speaker 1: the proposed event a quark nova. It would occur after
38:46
Speaker 1: the original supernova, rather than replacing it. The delay could
38:50
Speaker 1: range widely depending on the model, and the evolving remnant
38:54
Speaker 1: material from the first explosion would already be expanding outward
38:59
Speaker 1: when the second sho caught up with it. This interaction
39:02
Speaker 1: might create unusual light curves or chemical signatures that resemble
39:07
Speaker 1: exceptionally bright stellar explosions. No quark nova has been securely identified.
39:14
Speaker 1: The concept depends on uncertain physics at densities beyond direct
39:18
Speaker 1: experimental reach. Even so, it gives astronomers a testable idea.
39:25
Speaker 1: An unusually complicated explosion could be more than one catastrophe
39:29
Speaker 1: layered together. A star might collapse once through gravity and
39:34
Speaker 1: then irrupt again because matter deep inside it changed its
39:39
Speaker 1: fundamental form. Some neutron stars suddenly spin faster for reasons
39:44
Speaker 1: still debated. Pulsars are famous for gradually slowing as they
39:49
Speaker 1: lose rotational energy, yet some abruptly do the opposite. Their
39:54
Speaker 1: measured rotation jumps forward, in an event known as a glitch.
39:59
Speaker 1: The change can be tiny, but pulsar timing is so
40:02
Speaker 1: precise that astronomers notice immediately afterward. The star may spend
40:08
Speaker 1: days or months relaxing toward its previous behavior. The leading
40:13
Speaker 1: explanation involves the extraordinary interior of the neutron star. Beneath
40:19
Speaker 1: the rigid crust lies matter thought to include a neutron superfluid.
40:24
Speaker 1: Tiny vortices within that superfluid carry rotation. Some may become
40:30
Speaker 1: pinned to structures in the crust, while the outer star
40:33
Speaker 1: slowly loses speed. A growing mismatch develops between the two regions. Eventually,
40:40
Speaker 1: many vortices can shift at once and transfer angular momentum outward.
40:46
Speaker 1: The crust suddenly speeds up. That elegant picture explains several
40:51
Speaker 1: features of glitches, but not every observation fits neatly. Some
40:57
Speaker 1: stars recover unusually, Others show accompanying changes in radiation. Gleitches
41:03
Speaker 1: therefore offer something remarkable. A change in timing, measured from
41:08
Speaker 1: thousands of light years away can reveal how invisible matter
41:12
Speaker 1: moves beneath the surface of one of the densest objects
41:15
Speaker 1: in existence. Binary pulsars let astronomers test gravity under exceptionally
41:21
Speaker 1: extreme conditions. When two compact stars orbit each other, gravity
41:27
Speaker 1: becomes strong enough to expose effects too subtle for ordinary
41:30
Speaker 1: planetary systems. The famous Hulse tailor pulsar provided one of
41:35
Speaker 1: the earliest dramatic examples. Its radio pulses allowed astronomers to
41:40
Speaker 1: measure the orbit with extraordinary precision. Over time, the orbital
41:45
Speaker 1: period was found to shrink exactly as expected if the
41:48
Speaker 1: system were losing energy through gravitational waves. This happened decades
41:53
Speaker 1: before those waves were detected directly on Earth, and even
41:57
Speaker 1: more powerful laboratory appeared with the discovery of the double
42:01
Speaker 1: pulsar system. Both objects are neutron stars, and both can
42:06
Speaker 1: be tracked as they race around a shared center of mass.
42:10
Speaker 1: Relativity predicts several unusual effects in such systems. Orbits slowly rotate,
42:18
Speaker 1: signals experienced delays while passing through curved space time The
42:23
Speaker 1: stars themselves can alter how quickly clocks appear to run.
42:28
Speaker 1: Measurements repeatedly agree with Einstein's theory to remarkable precision. These
42:33
Speaker 1: systems are valuable because they perform experiments that no laboratory
42:37
Speaker 1: could build. Nature places stellar masses into close orbits, then
42:42
Speaker 1: pulsars provide timing signals precise enough for humanity to watch
42:47
Speaker 1: gravity reveal its most demanding behaviour. One magnetar flare briefly
42:52
Speaker 1: altered Earth's upper atmosphere from across the galaxy on December
42:57
Speaker 1: twenty seven. In two thousand four, a distance stellar remnant
43:00
Speaker 1: released a flash so intense that its effects reached our planet.
43:06
Speaker 1: The source was the magnetar SARS eighteen zero six minus twenty.
43:14
Speaker 1: A sudden rearrangement of its immense magnetic field produced a
43:18
Speaker 1: giant flare dominated by high energy radiation. The initial pulse
43:23
Speaker 1: lasted only a fraction of a second, yet satellites around
43:27
Speaker 1: Earth recorded an extraordinary burst. Instruments designed for other purposes
43:32
Speaker 1: were overwhelmed. More astonishingly, the radiation disturbed electrically charged layers
43:39
Speaker 1: high in Earth's atmosphere. Despite traveling across tens of thousands
43:44
Speaker 1: of like years. First magnetar giant flares are extremely rare.
43:49
Speaker 1: Only a handful have been observed in our galaxy and
43:52
Speaker 1: its immediate neighborhood. The event showed just how much energy
43:56
Speaker 1: can be stored in the magnetic field of a compact
43:59
Speaker 1: stellar remnant. Nothing physically traveled from the magnetar to Earth
44:04
Speaker 1: at dangerous speeds beyond the radiation itself. Even so, an
44:09
Speaker 1: event on the far side of the Milky Way was
44:11
Speaker 1: powerful enough to produce measurable changes above our heads. A
44:16
Speaker 1: dead star briefly touched Earth without coming remotely close to it.
44:21
Speaker 1: Neutron star mountains may rise less than a centimeter high.
44:26
Speaker 1: Calling them mountains sounds almost absurd until gravity is considered.
44:31
Speaker 1: A neutron star has such a powerful gravitational field that
44:36
Speaker 1: any substantial bump on its surface would be crushed almost flat.
44:40
Speaker 1: Its crust can still support slight irregularities where one region
44:44
Speaker 1: rises above another. Depending on the star and the strength
44:48
Speaker 1: of its crust, the maximum height may be measured in
44:51
Speaker 1: centimeters rather than kilometers. Yet even such a tiny deformation
44:56
Speaker 1: can matter enormously. The material fantastically dense, so a microscopic
45:03
Speaker 1: looking feature can contain an extraordinary amount of mass by
45:07
Speaker 1: terrestrial standards. If the mountain is not perfectly aligned with
45:11
Speaker 1: the rotation axis, the spinning star could generate continuous gravitational waves.
45:17
Speaker 1: Researchers are searching for exactly those signals. Detecting them would
45:21
Speaker 1: reveal how strong neutron star crusts really are and how
45:25
Speaker 1: matter behaves under immense pressure. The phrase mountain therefore changes
45:32
Speaker 1: meaning completely on these objects. On Earth, mountains rise because
45:38
Speaker 1: rock can support kilometers of relief. On a neutron star,
45:43
Speaker 1: gravity is so severe that a feature shorter than a
45:46
Speaker 1: finger may represent one of the largest permanent landscapes the
45:50
Speaker 1: surface can physically sustain. Intermediate mass black holes remain surprisingly
45:56
Speaker 1: difficult to find. Astronomers know of black holes formed from stars,
46:01
Speaker 1: and they know of supermassive monsters containing millions or billions
46:05
Speaker 1: of solar masses. Between those groups lies a strangely elusive population.
46:11
Speaker 1: Intermediate mass black holes should contain hundreds or thousands of
46:15
Speaker 1: times the Sun's mass. Finding secure examples would help explain
46:20
Speaker 1: how the earliest giant black holes grew so quickly. Yet
46:25
Speaker 1: these middleweights are difficult to confirm because many do not
46:28
Speaker 1: feed brightly enough to announce themselves. Dense star clusters are
46:33
Speaker 1: promising places to search. If a hidden black hole siks
46:37
Speaker 1: at the center surrounding stars should move under its gravitational influence.
46:43
Speaker 1: Astronomers can also watch for unusually luminous X ray sources
46:48
Speaker 1: or gravitational waves produced when compact objects merge. Several strong
46:53
Speaker 1: candidates have emerged, but establishing their masses beyond doubt can
46:57
Speaker 1: be challenging. Their scarcity may hold important intimation about how
47:02
Speaker 1: black holes form. Perhaps they arise through repeated mergers inside clusters.
47:08
Speaker 1: Perhaps some are relics of unusually massive early stars. The
47:13
Speaker 1: gap between ordinary and supermassive black holes remains one of
47:17
Speaker 1: astronomy's most intriguing missing chapters because something must connect the
47:22
Speaker 1: two ends of the family. Wandering black holes may travel
47:27
Speaker 1: silently between the stars. A black hole does not need
47:31
Speaker 1: a companion star or glowing disc to exist. If an
47:35
Speaker 1: isolated stellar black hole moves through relatively empty space, it
47:40
Speaker 1: can become almost perfectly dark. Astronomers estimate that the Milky
47:44
Speaker 1: Way should contain many such remnants, because countless massive stars
47:49
Speaker 1: have already lived and died, most would be extraordinarily difficult
47:54
Speaker 1: to detect. One promising method uses gravity rather than light.
48:00
Speaker 1: When an unseen compact object passes nearly in front of
48:03
Speaker 1: a distant background star, its gravitational field bends and magnifies
48:08
Speaker 1: that stars light. This phenomenon is called gravitational microlensing. A
48:14
Speaker 1: massive lens can also make the apparent position of the
48:17
Speaker 1: background star shift slightly across the sky. By measuring both
48:22
Speaker 1: effects over months, astronomers can estimate the mass of the
48:26
Speaker 1: invisible object. Several long duration events have produced candidates for
48:31
Speaker 1: isolated black holes or heavy neutron stars. The technique allows
48:37
Speaker 1: scientists to find objects that emit practically nothing themselves. Somewhere
48:42
Speaker 1: between the visible stars. Dark stellar remnants may be traveling
48:46
Speaker 1: alone around the galaxy. We notice them only when chance
48:50
Speaker 1: alignment turns the light of another star into a temporary
48:53
Speaker 1: gravitational beacon. Some black holes are being launched from their
48:57
Speaker 1: host galaxies. Supermassive black hole normally sits near the center
49:03
Speaker 1: of its galaxy. Under the right conditions, gravity can throw
49:08
Speaker 1: one away. The process may occur after two galaxies merge.
49:13
Speaker 1: Their central black holes can spiral together and eventually collide.
49:18
Speaker 1: Gravitational waves carry energy away from the merger. If those
49:23
Speaker 1: waves are emitted more strongly in one direction, the newly
49:27
Speaker 1: formed black hole recoils in the opposite direction. The kick
49:32
Speaker 1: can reach thousands of kilometers per second, and extreme theoretical cases,
49:37
Speaker 1: that may be enough to shift the object far from
49:39
Speaker 1: the galactic center or even eject it completely. Astronomers search
49:45
Speaker 1: for these runaways by looking for quasars that appear displaced
49:49
Speaker 1: from their host galaxies or move at unusual speeds. Several
49:54
Speaker 1: intriguing candidates exist, although proving that a black hole has
49:58
Speaker 1: truly been kicked out is difficult. The consequences would be extraordinary.
50:04
Speaker 1: A galaxy could lose the object that once dominated its nucleus. Meanwhile,
50:09
Speaker 1: the expelled black hole might carry a small entourage of
50:12
Speaker 1: stars and gas into intergalactic space. Even the largest objects
50:18
Speaker 1: in galaxies are not guaranteed to remain where they formed.
50:22
Speaker 1: Primordial black holes might be smaller than ordinary astronomical objects.
50:28
Speaker 1: A black hole does not have to weigh as much
50:30
Speaker 1: as a star. If primordial black holes formed from dense
50:34
Speaker 1: fluctuations in the early universe, some could have begun with
50:38
Speaker 1: far smaller masses. General relativity allows this because the defining
50:44
Speaker 1: feature of a black hole is not enormous total mass.
50:49
Speaker 1: It is sufficient mass compressed within a small enough region.
50:53
Speaker 1: A primordial black hole with asteroid like mass could therefore
50:57
Speaker 1: possess an event horizon smaller than an natum, while still
51:01
Speaker 1: weighing billions of tons. Even lighter examples may have evaporated
51:06
Speaker 1: long ago through Hawking radiation. The possible range depends on
51:11
Speaker 1: exactly how conditions unfolded soon after the Big Bang. Searches
51:16
Speaker 1: have rued out primordial black holes as the sole source
51:19
Speaker 1: of dark matter across many mass ranges, but certain windows
51:23
Speaker 1: remain under investigation. Scientists look for their gravitational effects and
51:28
Speaker 1: for radiation associated with evaporation or accretion. If small, primordial
51:34
Speaker 1: black holes exist today, they would overturn the everyday idea
51:38
Speaker 1: that black holes must be colossal. Nature could hide immense
51:43
Speaker 1: mass inside objects whose gravitational boundaries are microscopically tiny. Created
51:48
Speaker 1: before ordinary stars had any opportunity to collapse, a black
51:52
Speaker 1: hole can orbit another black hole for millions of years.
51:56
Speaker 1: Binary black holes do not necessarily collide soon after becoming
52:00
Speaker 1: a pair. Two massive stars can evolve within the same
52:04
Speaker 1: system and eventually leave black holes orbiting one another. Supermassive
52:10
Speaker 1: black holes can also become bound after their host galaxies merge.
52:15
Speaker 1: Once paired, the optics may spend enormous stretches of time,
52:20
Speaker 1: slowly losing orbital energy. Their separation gradually decreases. When they
52:26
Speaker 1: become sufficiently close, gravitational wave emission takes over and drives
52:31
Speaker 1: an accelerating spiral toward merger. The final stage can last
52:36
Speaker 1: mere moments, even though the earlier dance persisted for millions
52:40
Speaker 1: or billions of years. No material surface ever touches because
52:45
Speaker 1: black holes have event horizons rather than solid exteriors. Instead,
52:51
Speaker 1: the geometry of space time becomes increasingly dynamic until the
52:55
Speaker 1: horizons combine. The result is a single, larger black coal
53:00
Speaker 1: that rings briefly as it settles into equilibrium. Gravitational wave
53:05
Speaker 1: observatories have detected many stellar mass mergers, allowing astronomers to
53:09
Speaker 1: reconstruct the final seconds of systems whose histories were unimaginably long.
53:15
Speaker 1: The detectable collision is therefore only the final heartbeat of
53:19
Speaker 1: a partnership that may have survived across a significant fraction
53:23
Speaker 1: of cosmic history. Rare tidal disruption events tear entire stars
53:29
Speaker 1: into glowing streams. A star that ventures too close to
53:33
Speaker 1: a massive black hole can be destroyed without ever crossing
53:36
Speaker 1: the event horizon. Intact, gravity pulls more strongly on the
53:40
Speaker 1: side of the star nearest the back hole than on
53:43
Speaker 1: the far side. Eventually, this difference overwhelms the star's own
53:48
Speaker 1: gravity and tears it apart. Astronomers call the catastrophe a
53:54
Speaker 1: tidal disruption event. Roughly half the shredded material may escape,
53:59
Speaker 1: while the rest remains gravitationally bound. That returning debris stretches
54:04
Speaker 1: into long streams before colliding and forming an intensely hot
54:08
Speaker 1: flow around the black hole. The system can brighten dramatically
54:12
Speaker 1: in ultraviolet light and X rays. In some cases, powerful
54:17
Speaker 1: jets also emerge. These events are valuable because they illuminate
54:23
Speaker 1: black holes that were previously dormant. Acquired galactic nucleus can
54:28
Speaker 1: suddenly become one of the brightest objects in its neighborhood
54:31
Speaker 1: after consuming a single unfortunate star. The flare then fades
54:37
Speaker 1: as the supply of debris dwindles. Astronomers effectively watch a
54:41
Speaker 1: black hole switch on for a temporary meal. Each event
54:45
Speaker 1: provides a rare opportunity to study extreme gravity by following
54:49
Speaker 1: the destruction of an individual star in real time. Some
54:54
Speaker 1: black holes feed so quickly they challenge accepted Groof limits.
55:00
Speaker 1: Approaching a black hole becomes extremely hot and luminous, that
55:04
Speaker 1: radiation pushes outward on the surrounding gas, creating a natural
55:09
Speaker 1: limit to how quickly material should fall inward under steady conditions.
55:13
Speaker 1: This benchmark is known as the Eddington limit. Yet astronomers
55:18
Speaker 1: have found black holes that appear to consume matter at
55:21
Speaker 1: rates above it. These super Eddington systems reveal that the
55:25
Speaker 1: textbook limit is not an absolute speed barrier. Thick accretion
55:30
Speaker 1: discs can trap radiation and carry some of its energy inward.
55:35
Speaker 1: Powerful winds may also remove excess material while allowing a
55:39
Speaker 1: substantial flow to continue toward the center. The question becomes
55:44
Speaker 1: especially important when astronomers observe enormous quasars. In the young universe,
55:50
Speaker 1: some black holes had already reached masses of billions of suns,
55:54
Speaker 1: surprisingly soon after cosmic history began. Standard growth from small
55:59
Speaker 1: stellar remnants can struggle to produce such giants quickly enough.
56:04
Speaker 1: Episodes of unusually rapid feeding may help solve the problem.
56:09
Speaker 1: A black hole can therefore enter a phase where its
56:12
Speaker 1: appetite appears to exceed the rate that its own radiation
56:15
Speaker 1: should normally permit, offering one possible route to creating cosmic
56:20
Speaker 1: giants in record time. Nearly dormant black holes can reveal
56:25
Speaker 1: themselves by bending background starlight. Some black holes have no
56:30
Speaker 1: glowing companion and almost nothing nearby to consume invisible light.
56:36
Speaker 1: They can be genuinely invisible, their gravity still leaves a
56:40
Speaker 1: detectable signature. If such an object cross is nearly in
56:44
Speaker 1: front of a more distant star, space time around the
56:47
Speaker 1: black hole acts like a lens. The background star temporarily
56:52
Speaker 1: becomes brighter because multiple bent paths send additional light toward Earth.
56:58
Speaker 1: Unlike ordinary eclipses, nothing needs to glow or block the
57:02
Speaker 1: star directly. The effect depends entirely on gravity. By monitoring
57:08
Speaker 1: dense fields of stars for years, surveys can find these
57:12
Speaker 1: rare microlensing events. The longest lasting cases are especially interesting
57:17
Speaker 1: because a more massive lens produces a slower event. Extremely
57:22
Speaker 1: precise astrometry adds another clue by measuring how the background
57:26
Speaker 1: stars apparent position shifts during the alignment. Together, the measurements
57:32
Speaker 1: can expose an otherwise dark compact object and estimate its mass.
57:38
Speaker 1: This method is remarkable because the black hole may never
57:41
Speaker 1: consume anything while astronomers are watching. It gives itself away
57:45
Speaker 1: simply by passing through the correct line of sight and
57:48
Speaker 1: changing the path taken by someone else's light. A few
57:52
Speaker 1: galaxies may contain two actively feeding central black holes. When
57:57
Speaker 1: galaxies collide, their stars largely pass one another without direct impact,
58:02
Speaker 1: but their central black holes begin a much slower encounter.
58:07
Speaker 1: Each black hole can retain surrounding gas as the two
58:10
Speaker 1: galactic cores draw together. If both are feeding at the
58:14
Speaker 1: same time, astronomers may observe a dual active galactic nucleus.
58:20
Speaker 1: These systems of valuable snapshots of a merger before the
58:23
Speaker 1: black holes themselves become a tight binary. They can reveal
58:28
Speaker 1: two luminous sources inside a galaxy whose structure has already
58:32
Speaker 1: been distorted by interaction. Finding genuine pairs requires careful work
58:38
Speaker 1: because bright star formation or jets can mimic some signatures.
58:44
Speaker 1: High resolution radio, X ray and infrared observations help separate
58:48
Speaker 1: the candidates. Eventually, dynamical friction should draw the central objects closer.
58:55
Speaker 1: What happens at very small separations connects directly to the
58:59
Speaker 1: creation of s supermassive black hole mergers and low frequency
59:03
Speaker 1: gravitational waves do. All active nuclei therefore capture a remarkable
59:09
Speaker 1: intermediate stage. Two galaxies that once evolved independently have begun
59:14
Speaker 1: becoming one, Yet for a limited period, each still carries
59:18
Speaker 1: a feeding central black hole. The future galaxy temporarily possesses
59:23
Speaker 1: two energetic hearts. Black hole mergers briefly radiate more power
59:29
Speaker 1: than all visible stars. The most violent part of a
59:33
Speaker 1: black hole merger lasts only a fraction of a second.
59:37
Speaker 1: During that instant, an extraordinary amount of energy leaves the
59:41
Speaker 1: system as gravitational waves. These are ripples in space time
59:46
Speaker 1: itself rather than ordinary light. When the first directed detected
59:51
Speaker 1: merger swept past Earth in two thousand fifteen, the two
59:55
Speaker 1: black holes combined into one. While several suns worth of
59:58
Speaker 1: mass energy disappeared from from the final mass budget, that
1:00:02
Speaker 1: energy was carried away by gravitational radiation. At peak output,
1:00:07
Speaker 1: the event produced more power than the combined light of
1:00:10
Speaker 1: the visible stars in the observable universe, Yet human eyes
1:00:15
Speaker 1: would have seen nothing because the energy was not primarily electromagnetic.
1:00:21
Speaker 1: By the time the waves reached Earth, after traveling for
1:00:24
Speaker 1: more than a billion years, they changed the length of
1:00:27
Speaker 1: detector arms by less than the width of a proton.
1:00:31
Speaker 1: That tiny movement revealed an event of almost incomprehensible power.
1:00:36
Speaker 1: Black holes can therefore collide in complete darkness while momentarily
1:00:40
Speaker 1: becoming the most energetic known engines in the cosmos. Through
1:00:44
Speaker 1: distortions of space and time alone, fast radio bursts can
1:00:48
Speaker 1: release astonishing energy within milliseconds. A radio telescope can stare
1:00:54
Speaker 1: into space and suddenly receive a flash that is over
1:00:58
Speaker 1: almost as soon as it begins. Fast radio bursts last
1:01:02
Speaker 1: for only milliseconds, yet many originating galaxies hundreds of millions
1:01:07
Speaker 1: or billions of light years away. To remain detectable across
1:01:11
Speaker 1: those distances, the source must release an extraordinary amount of
1:01:15
Speaker 1: radio energy in an extremely short interval. Their discovery created
1:01:21
Speaker 1: a major astronomical mystery, because the first events appeared without
1:01:25
Speaker 1: warning and did not immediately repeat. Today, astronomers know that
1:01:31
Speaker 1: at least some are connected to highly magnetized neutron stars.
1:01:36
Speaker 1: A magnetar inside our own galaxy produced a powerful radio
1:01:40
Speaker 1: burst in twenty twenty that strongly linked these objects to
1:01:44
Speaker 1: the phenomenon. That does not necessarily mean every burst has
1:01:48
Speaker 1: the same origin. Different environments may create similar flashes. Their
1:01:54
Speaker 1: signals also pass through intergalactic material before reaching Earth. The
1:01:58
Speaker 1: resulting delay between in radio frequencies, let's researchers estimate how
1:02:02
Speaker 1: much ionized matter lies along the route. A millisecond burst
1:02:07
Speaker 1: can therefore do more than announce an extreme event. It
1:02:11
Speaker 1: can probe otherwise difficult two s material across enormous cosmic distances.
1:02:17
Speaker 1: Some repeating radio bursts follow mysterious cycles lasting many days.
1:02:22
Speaker 1: Not every fast radio burst source behaves randomly. A few
1:02:27
Speaker 1: repeaters seem to become active during recurring windows. One famous source,
1:02:32
Speaker 1: known as FRB eighteen zero nine one six J zero
1:02:38
Speaker 1: one five eight plus sixty five produces bursts during a
1:02:41
Speaker 1: cycle lasting roughly sixteen days. For part of that interval,
1:02:46
Speaker 1: radio flashes are much more likely to appear. Then the
1:02:50
Speaker 1: source becomes comparatively inactive before the pattern returns. Another repeater
1:02:56
Speaker 1: has shown a much longer cycle, measured in months. These
1:03:00
Speaker 1: rhythms provide clues about what surrounds the bursts source. One
1:03:04
Speaker 1: possibility is orbital motion. A neutron star may travel around
1:03:09
Speaker 1: a companion and become visible only when geometry or surrounding
1:03:13
Speaker 1: gas allows its radio emission to escape. Another possibility involves
1:03:19
Speaker 1: slow changes in the orientation of a rotating compact object.
1:03:24
Speaker 1: Researchers continue testing competing explanations because periodic behavior dramatically narrows
1:03:30
Speaker 1: the range of possible models. The source cannot simply be
1:03:34
Speaker 1: exploding once and disappearing. Something survives and resets. That transforms
1:03:42
Speaker 1: the mystery. Instead of asking what single catastrophe created the burst,
1:03:48
Speaker 1: astronomers can ask what cosmic machine repeatedly places itself into
1:03:52
Speaker 1: exactly the right condition to flash across the universe again.
1:03:57
Speaker 1: Long gamma ray bursts announce the deaths of an usually
1:04:00
Speaker 1: massive stars. A long gamma ray burst can begin when
1:04:04
Speaker 1: the core of an enormous star collapses and fails to
1:04:08
Speaker 1: produce an ordinary explosion. The center forms a black hole
1:04:13
Speaker 1: or possibly an extremely magnetized neutron star. Meanwhile, material continues
1:04:19
Speaker 1: falling inward and creates a rapidly rotating disc. Under suitable conditions,
1:04:26
Speaker 1: the central engine launches narrow jets that punch through the
1:04:29
Speaker 1: collapsing star at almost the speed of light. If one
1:04:34
Speaker 1: jet points toward Earth, satellites detect a burst of gamma
1:04:38
Speaker 1: radiation that can last from several seconds to many minutes.
1:04:43
Speaker 1: After the high energy fash fades, astronomers often discover a
1:04:47
Speaker 1: broad lined type of stellar explosion beneath it. These associations
1:04:52
Speaker 1: helped to establish the connection between long bursts and the
1:04:55
Speaker 1: deaths of stripped massive stars. The event is directlytional. An
1:05:01
Speaker 1: identical collapse occurring with its jet pointed elsewhere, might never
1:05:05
Speaker 1: be recognized from Earth as a gamma ray burst. That
1:05:09
Speaker 1: makes the phenomenon rarer to us than the underlying explosions themselves.
1:05:14
Speaker 1: What we observe is, therefore, a special alignment with one
1:05:18
Speaker 1: of nature's most powerful stellar deaths, seen almost directly down
1:05:23
Speaker 1: the barrel of a relativistic jet. Short gamma ray bursts
1:05:27
Speaker 1: often mark collisions between compact stellar remains. For years, astronomers
1:05:33
Speaker 1: suspected that brief gamma ray bursts came from merging neutron stars,
1:05:38
Speaker 1: but decisive evidence arrived only when several different messengers reached
1:05:42
Speaker 1: Earth from the same event. In August of twenty seventeen,
1:05:47
Speaker 1: gravitational wave detectors registered two neutron stars spiraling together. Less
1:05:53
Speaker 1: than two seconds later, satellites detected a short gamma ray
1:05:57
Speaker 1: burst from the same region of sky. Telescopes then found
1:06:01
Speaker 1: a new source of visible and infrared light in a
1:06:04
Speaker 1: distant galaxy. The sequence linked compact object mergers directly to
1:06:10
Speaker 1: at least some short bursts. Their brevity now makes sense.
1:06:15
Speaker 1: The final collision happens extraordinarily quickly. A central black whole
1:06:20
Speaker 1: or massive neutron star can form while a disc of
1:06:23
Speaker 1: debris drives jats outward. If a jet is favorably oriented,
1:06:28
Speaker 1: gamma radiation escapes toward us. The discovery connected several branches
1:06:34
Speaker 1: of astronomy in one event. Gravitational waves revealed the motion
1:06:39
Speaker 1: of the dense objects, while light exposed the aftermath, a
1:06:43
Speaker 1: flash lasting less than a few seconds therefore marked the
1:06:47
Speaker 1: ending of a binary system that had probably spent immense
1:06:50
Speaker 1: stretches of time gradually spiraling toward one final collision. Superluminous
1:06:56
Speaker 1: supernovas shine far brighter than ordinary explode ding stars. Some
1:07:02
Speaker 1: stellar explosions refuse to fade at the brightness expected from
1:07:05
Speaker 1: familiar supernova physics. Superluminous supernovas can become tens of times
1:07:11
Speaker 1: brighter than typical examples and remain brilliant for extended periods.
1:07:17
Speaker 1: Producing that much visible light requires an additional source of
1:07:21
Speaker 1: energy beyond the mechanisms that power many ordinary stellar deaths.
1:07:26
Speaker 1: One leading explanation involves a newborn magnetar spinning extremely rapidly
1:07:33
Speaker 1: as its rotation slows, Energy from the compact rimment can
1:07:37
Speaker 1: heat the expanding ejector from within. Another route may involve
1:07:41
Speaker 1: the explosion crashing into dense shells of material that the
1:07:45
Speaker 1: star expelled shortly before death. The collision converts kinetic energy
1:07:50
Speaker 1: into radiation. Individual events show enough variety that more than
1:07:56
Speaker 1: one mechanism may operate. Their rarity makes them misp specially
1:08:00
Speaker 1: valuable at great distances, because their immense luminosity allows telescopes
1:08:05
Speaker 1: to detect them across much of cosmic history. They also
1:08:09
Speaker 1: reveal that some massive stars undergo extraordinary changes shortly before collapse.
1:08:16
Speaker 1: A supernova is already the destruction of a star a
1:08:21
Speaker 1: superluminous one, requires nature to find a way of making
1:08:24
Speaker 1: that destruction dramatically brighter than the standard catastrophe. Pair instability
1:08:30
Speaker 1: supernovas may destroy giant stars without leaving remnants. A sufficiently
1:08:35
Speaker 1: massive stellar core can encounter a remarkable problem caused by
1:08:39
Speaker 1: its own temperature. High energy photons normally help provide pressure
1:08:44
Speaker 1: that supports the star against gravity. At extreme temperatures, some
1:08:49
Speaker 1: of those photons can transform into electron and positron pairs.
1:08:55
Speaker 1: Energy that had been supporting the core is suddenly diverted
1:08:59
Speaker 1: into creating articles. Pressure drops, gravity winds temporarily, and the
1:09:04
Speaker 1: core contracts. The contraction dried temperatures even higher and can
1:09:10
Speaker 1: ignite oxygen explosively. For stars within the right mass range,
1:09:15
Speaker 1: the resulting thermonuclear runaway may release enough energy to tear
1:09:20
Speaker 1: the entire star apart. No neutron star is left behind,
1:09:26
Speaker 1: no black hole necessarily remains. The star can simply disperse
1:09:31
Speaker 1: itself into space. This predicted event is called a pair
1:09:36
Speaker 1: instability supernova researchers continue searching for unambiguous examples because several
1:09:43
Speaker 1: exceptionally bright explosions have shown suggestive features without settling the
1:09:48
Speaker 1: question completely. The mechanism is striking because the star is
1:09:52
Speaker 1: not primarily destroyed by a collapsing iron core. Instead, the
1:09:57
Speaker 1: physics of light itself under my lends the pressure holding
1:10:01
Speaker 1: the star together and triggers an explosion powerful enough to
1:10:05
Speaker 1: erase the original object. Till Lenovas forge heavy elements inside
1:10:10
Speaker 1: rapidly expanding radioactive debris. After two neutron stars collide, the
1:10:16
Speaker 1: debris does not simply cool and disappear. It becomes a
1:10:21
Speaker 1: rapidly changing nuclear laboratory. Mater expelled from the merger contains
1:10:28
Speaker 1: an extraordinary abundance of free neutrons. Atomic nuclei capture them
1:10:34
Speaker 1: faster than radioactive decay can keep up. This rapid neutron
1:10:38
Speaker 1: capture process builds extremely heavy nuclei that ordinary Stella fusion
1:10:44
Speaker 1: cannot easily produce. Many of the newborn isotopes are unstable.
1:10:50
Speaker 1: As they decay toward more stable forms, they release energy
1:10:53
Speaker 1: that heats the expanding debris. That radioactive heating creates the
1:10:58
Speaker 1: glow astronomer's core a killinova. The color can change as
1:11:04
Speaker 1: different elements dominate the opacity of the ejector. Material containing
1:11:09
Speaker 1: lanthanides blocks visible light efficiently and shifts much of the
1:11:13
Speaker 1: emission toward infrared wavelengths. Observations of the famous merger in
1:11:18
Speaker 1: twenty seventeen showed this evolution unfolding over days. Killinovas therefore
1:11:25
Speaker 1: allow astronomers to watch fresh heavy elements announce their own
1:11:29
Speaker 1: creation through radioactive decay. Unlike a supernova powered mainly by
1:11:35
Speaker 1: the destruction of a large star, this transient records the
1:11:38
Speaker 1: aftermath of two compact remnants, combining and manufacturing new atomic
1:11:43
Speaker 1: species as their debris races outward. Failed supernovas may form
1:11:48
Speaker 1: black holes without brilliant visible explosions. Astronomers usually expect the
1:11:54
Speaker 1: death of a massive star to announce itself with a
1:11:57
Speaker 1: spectacular supernova predicts that some stars may instead disappear with
1:12:03
Speaker 1: surprisingly little display. If the collapsing core forms a black
1:12:08
Speaker 1: hole and the outward shock cannot successfully eject the stellar envelope,
1:12:13
Speaker 1: much of the star can fall inward. The result is
1:12:16
Speaker 1: sometimes called a failed supernova. Searching for one requires an
1:12:22
Speaker 1: unusual strategy, rather than looking for something new appearing in
1:12:27
Speaker 1: the sky. Astronomers repeatedly photograph nearby galaxies and ask whether
1:12:32
Speaker 1: a known massive star has vanished. One celebrated candidate involved
1:12:37
Speaker 1: a red supergiant in galaxy n g C six nine
1:12:40
Speaker 1: four six. It briefly brightened, then faded dramatically until its
1:12:45
Speaker 1: visible emission became extremely weak. Researchers have debated whether the
1:12:50
Speaker 1: star truly collapsed into a black hole or became hidden
1:12:54
Speaker 1: behind newly formed dust. That uncertainty shows how difficult the
1:12:58
Speaker 1: search is. A successful detection would reveal a route to
1:13:03
Speaker 1: black hole formation, but avoids the brilliant explosion normally associated
1:13:08
Speaker 1: with massive stellar death. One of the universe's most dramatic
1:13:12
Speaker 1: transformations could happen through disappearance rather than spectacle. Calcium rich
1:13:17
Speaker 1: explosions occur far from the galaxies that produce their stars.
1:13:22
Speaker 1: Some rare stellar transients appear in places where very few
1:13:26
Speaker 1: stars should be dying at all. Calcium rich explosions often
1:13:31
Speaker 1: occur far outside the bright regions of their host galaxies.
1:13:35
Speaker 1: After they fade, their spectra show unusually strong emission from
1:13:39
Speaker 1: calcium compared with many familiar supernova types. The combination has
1:13:45
Speaker 1: puzzled astronomers for years. Whatever progenitor creates them must either
1:13:50
Speaker 1: travel a long distance before exploding or belong to an
1:13:53
Speaker 1: old stellar population spread through faint galactic outskirts. Proposed explanations
1:13:59
Speaker 1: include unusual thermonuclear explosions involving white dwarfs and destructive encounters
1:14:06
Speaker 1: between compact stellar remnants. No single model has yet explained
1:14:11
Speaker 1: every observed event. Their remote locations make the puzzle more intriguing,
1:14:16
Speaker 1: because young massive stars normally die close to the regions
1:14:20
Speaker 1: where they formed, calcium rich transients seem disconnected from those nurseries.
1:14:27
Speaker 1: They may also contribute disproportionately to the distribution of calcium
1:14:31
Speaker 1: outside galaxies because their ejector are released directly into sparse
1:14:36
Speaker 1: surroundings rather than dense galactic disks. A relatively faint explosion
1:14:41
Speaker 1: on the edge of nowhere could therefore help seed intergalactic
1:14:44
Speaker 1: space with an element essential to rocky planets and living bones.
1:14:49
Speaker 1: Rare luminous red nova revealed two stars merging into one.
1:14:55
Speaker 1: Sometimes a stellar system does not end with an explosion
1:14:58
Speaker 1: that destroys both participants. Two ordinary stars can instead spiral
1:15:04
Speaker 1: together and merge as their orbit titans. One star may
1:15:09
Speaker 1: become engulfed in the atmosphere of the other. Friction removes
1:15:13
Speaker 1: orbital energy and drives the pair closer until their structures
1:15:17
Speaker 1: can no longer remain separate. The merger ejects gas and
1:15:22
Speaker 1: produces a transient that brightens dramatically before becoming strikingly red
1:15:28
Speaker 1: as the material cools. Astronomers call these events luminous red nova.
1:15:35
Speaker 1: One of the most famous examples involved V thirteen zero
1:15:38
Speaker 1: nine SCORPII. Remarkably, observations taken before its eruption showed a
1:15:44
Speaker 1: contact binary whose orbital period was shrinking. The system then
1:15:50
Speaker 1: produced a red transient consistent with the stars combining. This
1:15:55
Speaker 1: gave astronomers the rare chance to recognize a merger both
1:15:58
Speaker 1: before and after it happened. Other luminous red nova have
1:16:03
Speaker 1: revealed expanding shells of molecules and dust around their remnants.
1:16:08
Speaker 1: These events show that stellar evolution is not always a
1:16:12
Speaker 1: story of solitary stars. Sometimes two suns spend their final
1:16:17
Speaker 1: shared orbit becoming a single new object. Some galaxies stopped
1:16:22
Speaker 1: forming stars when the universe was still young. Astronomers have
1:16:27
Speaker 1: found distant galaxies that appear to have shut down star
1:16:30
Speaker 1: formation surprisingly early in cosmic history. This is difficult to explain,
1:16:36
Speaker 1: because young galaxies should contain plentiful gas for making new stars. Instead,
1:16:42
Speaker 1: these systems became quiescent while the universe was still only
1:16:47
Speaker 1: a fraction of its present age. Something had apparently removed
1:16:51
Speaker 1: their fuel or prevented it from cooling into new stellar nurseries.
1:16:56
Speaker 1: A rapidly feeding central black hole is one possible culprit,
1:17:00
Speaker 1: because powerful outflows can heat or expel enormous quantities of gas.
1:17:05
Speaker 1: Violent bursts of star formation may also consume available material
1:17:10
Speaker 1: faster than it can be replaced. The discovery of these
1:17:14
Speaker 1: early dormant galaxies has become especially important with powerful infrared
1:17:20
Speaker 1: telescopes that can examine their ancient starlight in greater detail.
1:17:25
Speaker 1: Their existence means galaxy evolution could move remarkably quickly. A
1:17:31
Speaker 1: system could assemble a large population of stars and then
1:17:34
Speaker 1: effectively switch off within a relatively short cosmic interval. Instead
1:17:39
Speaker 1: of seeing the early universe as a place where every
1:17:41
Speaker 1: galaxy was busily growing, astronomers are finding surprisingly mature systems
1:17:46
Speaker 1: that had already completed much of their stellar development. Ultratif
1:17:50
Speaker 1: fuse galaxies are enormous yet contain remarkably few visible stars.
1:17:56
Speaker 1: Some galaxies occupy an area comparable to the Milky Way,
1:17:59
Speaker 1: while produce using only a tiny fraction of its light.
1:18:03
Speaker 1: These ghostly systems are called ultra diffuse galaxies. Their stars
1:18:08
Speaker 1: are spread so thinly that the galaxy can almost disappear
1:18:12
Speaker 1: against the background sky. At first, astronomers wondered whether they
1:18:17
Speaker 1: were failed versions of large galaxies that somehow lost the
1:18:20
Speaker 1: ability to build substantial stellar populations. The reality appears more complicated.
1:18:27
Speaker 1: Some contain abundant dark matter, while others have produced controversial
1:18:32
Speaker 1: evidence for surprisingly little of it. Their histories may include
1:18:36
Speaker 1: strong stellar feedback or unusual interactions inside crowded galaxy clusters.
1:18:42
Speaker 1: One possibility is that gas was removed before many stars
1:18:45
Speaker 1: could form. Another is that the galaxy began with unusually
1:18:50
Speaker 1: high rotation and became spread across a larger region. Their
1:18:55
Speaker 1: faintness makes them challenging to discover, because ordinary surveys can
1:18:59
Speaker 1: overlook objects with such low surface brightness. At once recognized,
1:19:04
Speaker 1: they reveal an important lesson. A galaxy's physical size does
1:19:09
Speaker 1: not tell you how many stars it contains. Nature can
1:19:13
Speaker 1: build something vast enough to span tens of thousands of
1:19:17
Speaker 1: light years and still leave it almost transparent. Green Pea
1:19:21
Speaker 1: galaxies produce new stars at extraordinary rates. They received their
1:19:26
Speaker 1: playful name because early survey images showed them as tiny
1:19:30
Speaker 1: green dots. Behind that appearance are compact galaxies undergoing furious
1:19:35
Speaker 1: episodes of star formation. Their unusual colour comes largely from
1:19:40
Speaker 1: strongly glowing oxygen in clouds of gas heated by young stars.
1:19:46
Speaker 1: Although these galaxies are relatively small, they can produce new
1:19:49
Speaker 1: stars at a rate that seems wildly disproportionate to their size.
1:19:54
Speaker 1: That makes them useful nearby counterparts to intensely star forming
1:19:58
Speaker 1: galaxies from the distant use astronomers can study them in
1:20:03
Speaker 1: much greater detail than objects whose light has traveled for
1:20:06
Speaker 1: most of cosmic history. Some green pea galaxies also allow
1:20:11
Speaker 1: significant amounts of energetic ultraviolet radiation to escape. This matters
1:20:16
Speaker 1: because similar radiation from early galaxies is thought to have
1:20:19
Speaker 1: transformed neutral hydrogen throughout the young cosmos during the era
1:20:24
Speaker 1: of reionization. By studying these peculiar little systems, researchers can
1:20:29
Speaker 1: investigate a process that reshaped the entire universe. Their memorable
1:20:35
Speaker 1: name hide serious astrophysics. A modest galaxy appearing as little
1:20:40
Speaker 1: more than a colored speck can become a laboratory for
1:20:44
Speaker 1: understanding how young stars once change the state of matter
1:20:47
Speaker 1: across intergalactic space. Ring galaxies can form when another galaxy
1:20:53
Speaker 1: punches through their centers. One of the strangest galactic shapes
1:20:57
Speaker 1: can begin with an almost direct collision. If a smaller
1:21:01
Speaker 1: galaxy travels through the central region of a larger disc,
1:21:04
Speaker 1: gravity can send a disturbance spreading outward through the larger galaxy.
1:21:09
Speaker 1: Gas becomes compressed along the moving wave and begins producing
1:21:13
Speaker 1: new stars. The result can resemble an enormous, luminous ring
1:21:18
Speaker 1: surrounding a comparatively empty looking centre. The Cartwheel galaxy is
1:21:24
Speaker 1: a spectacular example. Its outer ring contains vigorous star formation
1:21:29
Speaker 1: triggered by an ancient encounter. The collision did not make
1:21:33
Speaker 1: billions of stars physically fly outward together like debris from
1:21:37
Speaker 1: an explosion. Instead, the disturbance moved through the existing galactic
1:21:43
Speaker 1: disc and altered where gas became dense enough to form stars.
1:21:48
Speaker 1: This distinction helps explain how a recognizable ring can continue
1:21:51
Speaker 1: expanding through a galaxy Over time. The shape will change
1:21:56
Speaker 1: as the system evolves and gravitational disturbances fade. Ring galaxies
1:22:01
Speaker 1: are uncommon because the collision geometry must be unusually well aligned.
1:22:06
Speaker 1: Most galactic encounters produce distortions without creating such striking symmetry. Occasionally, however,
1:22:13
Speaker 1: one galaxy passes through another at just the right angle
1:22:17
Speaker 1: and leaves behind a structure spanning tens of thousands of
1:22:21
Speaker 1: light years. Polar Ring galaxies rotate in two nearly perpendicular directions.
1:22:27
Speaker 1: Most galaxies have a dominant plane where their stars and
1:22:31
Speaker 1: gas orbit the center. Polar ring galaxies add a second
1:22:35
Speaker 1: structure that travels almost at right angles to the first.
1:22:39
Speaker 1: From the correct viewpoint, the system can resemble one galaxy
1:22:43
Speaker 1: wrapped inside another. The central body may look relatively ordinary,
1:22:48
Speaker 1: while a vast ring of gas and stars circles over
1:22:51
Speaker 1: its poles. Astronomers think these configurations often arise when galaxies
1:22:56
Speaker 1: interact and one system captures material from another. Instead of
1:23:01
Speaker 1: settling into the main galactic disc, the stolen gas can
1:23:05
Speaker 1: remain on a dramatically tilted orbit and eventually form stars there.
1:23:10
Speaker 1: Because the polar material moves through a different orientation, its
1:23:15
Speaker 1: speed gives researchers a valuable way to investigate the galaxy's
1:23:19
Speaker 1: gravitational field in three dimensions that can reveal how unseen
1:23:24
Speaker 1: mass is distributed around the system. The structure is also
1:23:28
Speaker 1: surprisingly durable. A well established polar ring can survive for
1:23:33
Speaker 1: billions of years, rather than immediately collapsing into the central plane.
1:23:38
Speaker 1: These galaxies preserve evidence of ancient encounters in their geometry.
1:23:43
Speaker 1: Their unusual appearance is essentially a record of matter arriving
1:23:47
Speaker 1: from a direction that ordinary galaxy formation never intended. Compact
1:23:52
Speaker 1: elliptical galaxies may be the stripped hearts of larger systems.
1:23:57
Speaker 1: A compact elliptical can contain billions of star stars squeezed
1:24:01
Speaker 1: into a remarkably small region. One way to create such
1:24:05
Speaker 1: an object may be to take a much larger galaxy
1:24:08
Speaker 1: and remove most of its outer material. This can happen
1:24:12
Speaker 1: near a massive neighbour. Repeated gravitational encounters pull away loosely
1:24:17
Speaker 1: bound stars from the outskirts, while the dense central region survives.
1:24:22
Speaker 1: What remains is not necessarily a galaxy that was born tiny.
1:24:27
Speaker 1: It may be the exposed core of something once far larger.
1:24:32
Speaker 1: The famous galaxy M three two near Andromeda has long
1:24:36
Speaker 1: been studied as a nearby example of this compact class.
1:24:40
Speaker 1: Its stellar population and structure provide clues about whether stripping
1:24:44
Speaker 1: shaped its present form. Astronomers have also discovered compact ellipticals
1:24:49
Speaker 1: surrounded by streams of stars that strongly support this destructive pathway.
1:24:55
Speaker 1: The idea gives s galactic archaeology a dramatic twist. Instead
1:25:00
Speaker 1: of reconstructing a lost object from fossils or debris on
1:25:03
Speaker 1: a planet, researchers can study a surviving galactic nucleus while
1:25:08
Speaker 1: its former outer stars disperse through space. The small, dense
1:25:13
Speaker 1: galaxy may therefore be the remaining center of a system that,
1:25:16
Speaker 1: once extended across a much greater volume. Dark galaxies could
1:25:21
Speaker 1: contain gas and dark matter, but almost no stars. Astronomers
1:25:27
Speaker 1: use the term dark galaxy for a particularly elusive possibility.
1:25:33
Speaker 1: Such an object would possess enough matter to behave gravitationally
1:25:37
Speaker 1: like a galaxy, but would have produced very few visible stars.
1:25:42
Speaker 1: Dark matter could dominate its mass, while neutral hydrogen provides
1:25:47
Speaker 1: detectable gas Without substantial starlight. However, the system would be
1:25:52
Speaker 1: extremely difficult to recognize. Radiotelescopes can search for hydrogen through
1:25:58
Speaker 1: a characteristic wavelength emitted by the atoms. Several candidates have
1:26:02
Speaker 1: appeared over the years, although many turned out to be
1:26:06
Speaker 1: tidal debris or extremely faint conventional galaxies after closer examination.
1:26:12
Speaker 1: That uncertainty is important because a convincing dark galaxy would
1:26:16
Speaker 1: test theories of galaxy formation. Computer simulations predict that numerous
1:26:21
Speaker 1: small dark matter haloes should exist, yet many contain no
1:26:26
Speaker 1: obvious stellar system. Some may simply have failed to gather
1:26:30
Speaker 1: enough gas, Others may have lost their material before star
1:26:34
Speaker 1: formation began. Finding an essentially starless galaxy would reveal a
1:26:39
Speaker 1: stage of cosmic construction that normally remains invisible. It would
1:26:44
Speaker 1: show that assembling a gravitational structure and lighting it with
1:26:48
Speaker 1: stars as separate achievements and nature may sometimes accomplily show
1:26:52
Speaker 1: me the first jellyfish. Galaxies trail streams of gas while
1:26:57
Speaker 1: crossing crowded galaxy clusters. A galaxy falling through a cluster
1:27:02
Speaker 1: can experience something that resembles an enormous cosmic headwind. The
1:27:07
Speaker 1: space between cluster galaxies is not empty. It contains hot,
1:27:13
Speaker 1: diffuse gas. As a galaxy races through that environment, pressure
1:27:18
Speaker 1: from the surrounding material can strip away its own gas
1:27:21
Speaker 1: and stretch it into long trailing structures. This process is
1:27:26
Speaker 1: called ram pressure stripping. Viewed through a telescope, the resulting
1:27:31
Speaker 1: galaxy can resemble a jellyfish with luminous tentacles extending behind it.
1:27:37
Speaker 1: Those tails are not merely in the debris. Compressed gas
1:27:41
Speaker 1: within them can form new stars outside the galaxy's main disc. Eventually, however,
1:27:47
Speaker 1: stripping removes the raw material needed for future star formation
1:27:52
Speaker 1: inside the galaxy itself. The same process that creates a
1:27:56
Speaker 1: spectacular appearance can therefore help shut the galaxy dow. Jellyfish
1:28:01
Speaker 1: galaxies let astronomers watch environment transform a stellar system while
1:28:06
Speaker 1: the process is actively occurring. A galaxy enters a dense
1:28:11
Speaker 1: cluster carrying its own reservoir of gas. Motion through the
1:28:15
Speaker 1: cluster then peels that reservoir away over cosmic time. This
1:28:20
Speaker 1: can turn a once productive spiral into a much quieter
1:28:24
Speaker 1: member of the crowded galactic community. Relic galaxies have remained
1:28:29
Speaker 1: almost unchanged since the early universe. Most large galaxies have
1:28:34
Speaker 1: endured mergers and prolonged episodes of growth. A rare few
1:28:38
Speaker 1: appear to have escaped much of that later history. These
1:28:42
Speaker 1: objects are sometimes called relic galaxies because though compact structures
1:28:47
Speaker 1: and ancient stellar populations resemble massive galaxies seen at much
1:28:52
Speaker 1: greater distances. One remarkable example lies surprisingly close to the
1:28:57
Speaker 1: Milky Way by cosmic standards. NGNGC twelve seventy seven contains
1:29:03
Speaker 1: an unusually dense concentration of old stars and shows little
1:29:07
Speaker 1: evidence that it accumulated the broad outer envelope expected from
1:29:12
Speaker 1: repeated mergers. Its stars seem to have formed rapidly long ago,
1:29:16
Speaker 1: before the system entered an extended period of relative isolation.
1:29:21
Speaker 1: That makes it valuable. Because astronomers normally study ancient galaxies
1:29:26
Speaker 1: by observing them across billions of like years, a nearby
1:29:30
Speaker 1: relic offers a much clearer view of similar conditions. Individual
1:29:35
Speaker 1: details that would be impossible to resolve in a very
1:29:37
Speaker 1: distant object become accessible. Such galaxies are not frozen in
1:29:42
Speaker 1: a literal sense. Their stars continue to age and orbit.
1:29:47
Speaker 1: What remained unusually preserved is the overall architecture. Finding one
1:29:54
Speaker 1: is like discovering an early chapter of galaxy formation, but
1:29:58
Speaker 1: somehow avoided being heavily reritch by everything that happened afterward.
1:30:02
Speaker 1: A few galaxies rotate without showing the expected influence of
1:30:06
Speaker 1: dark matter. Galaxy rotation normally provides some of the strongest
1:30:10
Speaker 1: evidence for invisible mass. Stars far from galactic centers often
1:30:16
Speaker 1: move too quickly to be held by visible matter alone.
1:30:20
Speaker 1: Yet a small number of unusual systems have been reported
1:30:24
Speaker 1: where measured motions can be explained with much less dark
1:30:27
Speaker 1: matter than expected. These claims remain difficult because the answer
1:30:33
Speaker 1: depends on distance and the orientation of the galaxy. Gas
1:30:38
Speaker 1: motions can also be affected by interactions that complicate mass estimates.
1:30:43
Speaker 1: One intriguing example is AGC eleven forty nine to zero five.
1:30:48
Speaker 1: Studies of its rotating hydrogen disk have suggested that ordinary
1:30:53
Speaker 1: matter may account for most of the observed gravitational pure
1:30:58
Speaker 1: Other researchers continue exams whether such systems genuinely lack dark matter,
1:31:03
Speaker 1: or whether measurement uncertainties can resolve the discrepancy. Either result
1:31:08
Speaker 1: would be informative. A securely confirmed galaxy with little dark
1:31:13
Speaker 1: matter would prove that visible and invisible matter can become
1:31:16
Speaker 1: dramatically separated during galaxy evolution. If improved observations restore a
1:31:23
Speaker 1: normal dark matter contribution, scientists learn how easily unusual geometry
1:31:28
Speaker 1: can mislead mass estimates. These rare galaxies are powerful precisely
1:31:33
Speaker 1: because they force astronomers to test one of modern cosmology's
1:31:37
Speaker 1: most familiar assumptions. Giant cosmic voids can span hundreds of
1:31:42
Speaker 1: millions of like years travel through one of the largest voids,
1:31:47
Speaker 1: and the universe would appear astonishingly sparse for an enormous distance.
1:31:53
Speaker 1: Galaxies do exist inside these regions, but they are far
1:31:57
Speaker 1: less numerous than average. The boundaries are where much of
1:32:01
Speaker 1: the missing matter is collected. Gravity gradually pulled material from
1:32:06
Speaker 1: under dense areas toward denser filaments as the universe evolved.
1:32:10
Speaker 1: This made voids larger and emptier over time. Some have
1:32:15
Speaker 1: diameters reaching hundreds of millions of light years. Their scale
1:32:20
Speaker 1: is difficult to grasp. Entire galaxy clusters could fit comfortably
1:32:25
Speaker 1: inside them while occupying only a small portion of the
1:32:28
Speaker 1: available volume. Voids also influence the motion of nearby galaxies
1:32:34
Speaker 1: because matter tends to flow away from their interiors towards
1:32:37
Speaker 1: surrounding structures. Astronomers map them using immense red shift surveys
1:32:43
Speaker 1: that reconstruct where galaxies sit in three dimensions. These apparently
1:32:49
Speaker 1: vacant spaces carry cosmological information because their sizes and shapes
1:32:54
Speaker 1: respond to how structure grew and how cosmic expansion changed.
1:32:59
Speaker 1: A void is the therefore not merely in absence. Ittentinus
1:33:05
Speaker 1: has a history. Matter once had opportunities to remain there,
1:33:09
Speaker 1: but gravity gradually concentrated much of it elsewhere and left
1:33:13
Speaker 1: behind a gigantic underpopulated region. Enormous galaxy walls stretch farther
1:33:19
Speaker 1: than many people imagine possible. Galaxies assemble into structures far
1:33:24
Speaker 1: larger than individual plusters. Some lie along immense sheets and
1:33:29
Speaker 1: filaments that can extend across extraordinary distances. These arrangements are
1:33:35
Speaker 1: often described as galaxy walls. The Slome Great War became
1:33:39
Speaker 1: famous when surveys revealed a connected concentration of galaxies stretching
1:33:44
Speaker 1: for more than a billion light years by some definitions.
1:33:48
Speaker 1: Even larger proposed structures have since been reported, although determining
1:33:52
Speaker 1: where one structure ends and another begins can be statistically complicated.
1:33:58
Speaker 1: These walls do not behave like solid objects. They are
1:34:02
Speaker 1: patterns in the distribution of countless galaxies separated by enormous gaps.
1:34:07
Speaker 1: Their existence grows naturally from the cosmic web that developed
1:34:11
Speaker 1: from small density variations in the early universe. Dense regions
1:34:16
Speaker 1: attracted additional matter and gradually became filaments or sheets surrounding
1:34:21
Speaker 1: emptier voids. Researchers compare the largest claimed structures with cosmological
1:34:27
Speaker 1: simulations to determine whether their sizes are unusual within the
1:34:32
Speaker 1: standard model. The results require careful interpretation because enormous patterns
1:34:38
Speaker 1: can arise by chants inside an even larger universe. Still,
1:34:43
Speaker 1: galaxy walls demonstrate how far gravity can organize matter. The
1:34:48
Speaker 1: universe possesses architecture on scales so great that even entire
1:34:52
Speaker 1: galaxy clusters become merely small features within a much broader structure.
1:34:58
Speaker 1: Rare gravitational lenses create nearly perfect rings of distant light.
1:35:03
Speaker 1: When a massive galaxy lies almost exactly between Earth and
1:35:07
Speaker 1: a more distant source, gravity can transform the background object
1:35:11
Speaker 1: into a luminous circle. This is called an Einstein ring.
1:35:18
Speaker 1: The foreground galaxy bends space time around itself. Light from
1:35:23
Speaker 1: the distant source therefore reaches Earth along several curved paths
1:35:27
Speaker 1: instead of traveling straight toward us. If the alignment is
1:35:31
Speaker 1: exceptionally precise, those distorted images connect into a ring around
1:35:36
Speaker 1: the lensing galaxy. The effect does not mean the background
1:35:40
Speaker 1: object is physically ring shaped. Its appearance has been reconstructed
1:35:45
Speaker 1: by gravity. Perfect or nearly perfect rings are uncommon because
1:35:49
Speaker 1: three objects must align with remarkable accuracy across enormous distances.
1:35:55
Speaker 1: Astronomers treasure them because the distortion provides a sensitive measurement
1:35:59
Speaker 1: of the mass in the foreground lens that includes matter
1:36:04
Speaker 1: producing little or no light. The gravitational magnification can also
1:36:09
Speaker 1: reveal distant galaxies that would otherwise be too faint to study.
1:36:14
Speaker 1: An Einstein ring therefore performs two jobs simultaneously. It maps
1:36:19
Speaker 1: the gravity of one galaxy while enlarging another that lies
1:36:23
Speaker 1: much farther away. A rare accident of geometry becomes a
1:36:27
Speaker 1: natural telescope built entirely from curved spacetime. Some quasars appear
1:36:33
Speaker 1: several times because spacetime bends their light. A single quasar
1:36:38
Speaker 1: can reach Earth along more than one route. If a
1:36:42
Speaker 1: massive galaxy or galaxy cluster lies between us and the quasar,
1:36:46
Speaker 1: its gravity bends the incoming light into separate paths. Telescopes
1:36:51
Speaker 1: may then record two or four apparent quasars surrounding the
1:36:55
Speaker 1: foreground lens. These are not identical objects that form together.
1:37:01
Speaker 1: They are multiple images of the same distant source. The
1:37:05
Speaker 1: paths have different lengths and pass through slightly different regions
1:37:09
Speaker 1: of curved space time. As a result, light from a
1:37:13
Speaker 1: flare in the quasar can reach one image days or
1:37:16
Speaker 1: months before the same change appears in another. Astronomers measure
1:37:21
Speaker 1: these delays with great precision. Combined with a model of
1:37:25
Speaker 1: the foreground mass, they can use the delays to estimate
1:37:28
Speaker 1: cosmic distances and investigate the expansion rate of the universe.
1:37:34
Speaker 1: The technique turns an optical illusion into a measuring instrument.
1:37:39
Speaker 1: It also means that observers can effectively watch the same
1:37:42
Speaker 1: quasar at slightly different moments in its history within one
1:37:45
Speaker 1: telescope image. Gravity has created separate arrival schedules for photons
1:37:50
Speaker 1: that began their journeys in the same extraordinarily distant galactic nuclears.
1:37:55
Speaker 1: Cosmic strings remain hypothetical relics from the universe's earliest moments.
1:38:01
Speaker 1: Some theories of the early universe predict that enormous concentrations
1:38:05
Speaker 1: of energy could have become trapped along extraordinarily thin lines.
1:38:10
Speaker 1: These hypothetical objects are called cosmic strings. They should not
1:38:14
Speaker 1: be confused with the tiny fundamental strings proposed in certain
1:38:19
Speaker 1: theories of particle physics. A cosmic string would instead be
1:38:23
Speaker 1: a defect formed as the young universe cooled and changed state.
1:38:28
Speaker 1: Although incredibly narrow, one could contain a tremendous amount of
1:38:32
Speaker 1: energy per unit length and potentially extend across astronomical distances.
1:38:37
Speaker 1: Its gravity would behave unusually, because space time around the
1:38:41
Speaker 1: string would have a distinctive geometry. A background galaxy could
1:38:46
Speaker 1: appear doubled if the string passed between that galaxy and Earth.
1:38:50
Speaker 1: Oscillating loops might also produce characteristic gravitational waves. Astronomers have
1:38:56
Speaker 1: searched for both kinds of signature without finding conclusive evidence.
1:39:01
Speaker 1: That absence places limits on how common or energetic cosmic
1:39:05
Speaker 1: strings could be. Their appeal comes from what a detection
1:39:09
Speaker 1: would mean. A surviving string would be a physical relic
1:39:13
Speaker 1: from processes occurring at energies far beyond any human experiment.
1:39:17
Speaker 1: Instead of merely inferring the early universe from its aftermath,
1:39:21
Speaker 1: scientists could be observing a defect created during one of
1:39:25
Speaker 1: its first major transformations. Domain walls could be ancient boundaries
1:39:30
Speaker 1: between different vacuum states. Imagine the early universe undergoing a
1:39:34
Speaker 1: phase transition while separate regions settle into different versions of
1:39:39
Speaker 1: the lowest energy state. Where those regions meet, theory allows
1:39:43
Speaker 1: a boundary called a domain war to form. Such a
1:39:48
Speaker 1: wall would not be made from ordinary atoms, it would
1:39:52
Speaker 1: be a structure in underlying fields extending across space. Similar
1:39:57
Speaker 1: mathematical behaviour appears in familiar physical systems when different regions
1:40:02
Speaker 1: choose different states during cooling. In cosmology, however, a stable
1:40:07
Speaker 1: domain wall could contain enormous energy and strongly influence the
1:40:11
Speaker 1: evolution of the universe. This creates a problem. If heavy
1:40:17
Speaker 1: walls were common and long lived, their gravitational effects should
1:40:21
Speaker 1: be obvious today, the fact that we do not see
1:40:24
Speaker 1: such domination places powerful restrictions on models that produce them.
1:40:29
Speaker 1: Some theories allow walls to decay early or form with
1:40:33
Speaker 1: properties that make them much less disruptive. Scientists have proposed
1:40:37
Speaker 1: possible signatures involving gravitational waves or subtle cosmological effects. None
1:40:44
Speaker 1: has established their existence. Domain walls remain fascinating because they
1:40:49
Speaker 1: turn an abstract idea into something potentially physical. Different regions
1:40:54
Speaker 1: of space could once have chosen different vacuum configurations and
1:40:59
Speaker 1: briefly carried real boundaries between them. Primordial magnetic fields may
1:41:04
Speaker 1: have survived since before galaxies formed. Magnetic fields thread planets
1:41:09
Speaker 1: and stars today, but astronomers still debate where the universe's
1:41:13
Speaker 1: earliest magnetism came from. One possibility is that weak seed
1:41:18
Speaker 1: fields appeared before galaxies existed. Processes during cosmic phase transitions
1:41:24
Speaker 1: or other events in the young universe might have generated them. Later,
1:41:29
Speaker 1: collapsing gas and turbulent motion inside galaxies could have amplified
1:41:34
Speaker 1: those tiny beginnings into the much stronger fields observed now.
1:41:39
Speaker 1: Another possibility is that magnetism arose later through astrophysical processes
1:41:44
Speaker 1: associated with the first stars and galaxies. Distinguishing these histories
1:41:49
Speaker 1: is difficult because magnetic fields do not shine by themselves.
1:41:54
Speaker 1: Researchers instead study how they influenced charged particles or alter
1:41:59
Speaker 1: the polarization of passing radiation. Gamma rays from distant sources
1:42:04
Speaker 1: can also provide indirect clues to weak magnetism in the
1:42:07
Speaker 1: vast spaces between galaxies. Evidence for truly primordial fields would
1:42:14
Speaker 1: be profound because their present structure could retain information from
1:42:18
Speaker 1: epochs otherwise hidden from direct observation. A magnetic field measured
1:42:23
Speaker 1: across an almost empty region of space might therefore have
1:42:27
Speaker 1: an ancestry reaching back far beyond the first galaxies. Magnetism
1:42:32
Speaker 1: could be carrying a faint physical memory from the universe
1:42:35
Speaker 1: before familiar cosmic structures had formed. Dark matter clumps might
1:42:40
Speaker 1: exist without any stars or gas. Dark matter does not
1:42:44
Speaker 1: need to shine in order to gather under gravity. Cosmological
1:42:48
Speaker 1: simulations predict that galaxies should be surrounded by numerous smaller
1:42:52
Speaker 1: dark matter concentrations, called subhellows. Some become homes for dwarf
1:42:57
Speaker 1: galaxies after ordinary gas settle inside them and form stars.
1:43:02
Speaker 1: Others may remain completely dark because they are too small
1:43:06
Speaker 1: to capture or retain enough gas. Such starless clumps would
1:43:10
Speaker 1: be almost impossible to photograph directly. Astronomers must search for
1:43:15
Speaker 1: their gravitational effects instead. A dark subhallow passing near a
1:43:20
Speaker 1: stream of stars can disturb the stream and leave a
1:43:24
Speaker 1: gap or kink. Similar invisible structures can alter the appearance
1:43:29
Speaker 1: of strongly lensed background objects. These subtle signatures allow researchers
1:43:35
Speaker 1: to test how lumpy dark matter really is on small scales.
1:43:40
Speaker 1: The results could distinguish between different ideas about the particles
1:43:43
Speaker 1: making up this mysterious substance. If many starless subhalows are
1:43:48
Speaker 1: eventually detected, they would help solve the long standing puzzle
1:43:53
Speaker 1: about why simulations predict more small structures than the number
1:43:57
Speaker 1: of visible satellite galaxies suggests entire gravitational structures may therefore
1:44:04
Speaker 1: surround the Milky Way while containing nothing that an ordinary
1:44:08
Speaker 1: telescope could ever photograph. Cosmic neutrinos preserve information from places
1:44:13
Speaker 1: light cannot escape. Ordinary light can be absorbed or scattered
1:44:18
Speaker 1: by dense matter before it escapes an energetic cosmic environment.
1:44:23
Speaker 1: Neutrinos have a much easier journey because they interact so weakly.
1:44:28
Speaker 1: They can emerge from regions that are effectively opaque to
1:44:32
Speaker 1: photons and travel enormous distances with little disturbance. This makes
1:44:38
Speaker 1: them unique astronomical messengers. The Sun provides a nearby example.
1:44:45
Speaker 1: Neutrinos produced in nuclear reactions at its center escape almost immediately,
1:44:51
Speaker 1: while energy carried by photons can take an immensely longer
1:44:55
Speaker 1: route through repeated interactions before reaching the surface. In violent
1:45:01
Speaker 1: objects beyond the Solar system, neutrinos can likewise carry information
1:45:05
Speaker 1: directly from deeply buried processes. The explosion of supernova nineteen
1:45:11
Speaker 1: eighty seven A produced a famous burst of detected neutrinos
1:45:15
Speaker 1: before the visible event reached its maximum brightness. Modern observatories
1:45:20
Speaker 1: now search for much higher energy examples from active galaxies
1:45:24
Speaker 1: and other extreme sources. The particles are extraordinarily difficult to
1:45:29
Speaker 1: detect precisely because they pass through matter so readily. When
1:45:33
Speaker 1: one finally interacts inside a detector, however, it can carry
1:45:37
Speaker 1: evidence from a region that electromagnetic radiation could not reveal
1:45:41
Speaker 1: in the same direct way. The oldest possible gravitational waves
1:45:46
Speaker 1: may come from cosmic inflation. If inflation occurred, the universe
1:45:51
Speaker 1: underwent an extraordinary burst of expansion during an extremely early
1:45:56
Speaker 1: fraction of its existence, quantum fluctuation present at that time
1:46:01
Speaker 1: could have produced gravitational waves with wavelengths later stretched to
1:46:05
Speaker 1: cosmic scales. These primordial waves would be far older than
1:46:10
Speaker 1: gravitational signals from colliding black holes. Because they would originate
1:46:15
Speaker 1: before stars or galaxies existed. Nobody has detected them conclusively.
1:46:21
Speaker 1: Their most famous potential signature lies in the polarization pattern
1:46:26
Speaker 1: of the cosmic microwave background. A specific swirling pattern called
1:46:31
Speaker 1: be mode polarization could preserve evidence of primordial gravitational waves.
1:46:39
Speaker 1: The search is difficult because dust within our own galaxy
1:46:43
Speaker 1: can produce polarization that mimics the desired signal. Experiments therefore
1:46:48
Speaker 1: observe multiple frequencies and compare large regions of sky to
1:46:53
Speaker 1: separate foreground contamination from cosmological effects. Other detectors asserting which
1:47:00
Speaker 1: for primordial gravitational backgrounds at very different frequencies. A confirmed
1:47:05
Speaker 1: detection would open an observational window onto a period inaccessible
1:47:09
Speaker 1: to ordinary telescopes. Light cannot show us inflation directly. Gravitational
1:47:16
Speaker 1: waves might. They could preserve physical information from an era
1:47:20
Speaker 1: so early, but the familiar particles and structures of the
1:47:24
Speaker 1: later universe had not yet taken their recognizable forms. Free
1:47:28
Speaker 1: floating planets travel through darkness without orbiting any star. Not
1:47:33
Speaker 1: every planet has a sunrise. Some worlds wander through interstellar
1:47:37
Speaker 1: space without being gravitationally bound to any star at all.
1:47:42
Speaker 1: Astronomers call them rogue or free floating planets. They may
1:47:47
Speaker 1: begin inside ordinary planetary systems and later be ejected when
1:47:53
Speaker 1: gravitational encounters destabilize their orbits. Others could possibly form more
1:47:58
Speaker 1: directly from collapsing clouds that never accumulate enough mass to
1:48:02
Speaker 1: ignite as stars. Finding these objects is difficult because they
1:48:07
Speaker 1: receive no nearby starlight to reflect. Gravitational microlensing provides one method.
1:48:14
Speaker 1: A rogue planet crossing in front of a distant star
1:48:17
Speaker 1: can briefly magnify that stars light even though the planet
1:48:21
Speaker 1: itself remains unseen. Young examples can also glow faintly and
1:48:26
Speaker 1: infrared because they retain heat from their formation. Estimates of
1:48:31
Speaker 1: their abundance remain uncertain, but surveys suggest they may represent
1:48:35
Speaker 1: a substantial hidden population. Conditions on such a world would
1:48:40
Speaker 1: be unlike those on Earth. Its sky would contain distant
1:48:45
Speaker 1: stars but no dominant sun. Yet internal heat or a
1:48:49
Speaker 1: thick atmosphere could potentially keep some environments warmer than expected.
1:48:54
Speaker 1: Tanatary existence does not necessarily require permanent membership in a
1:48:58
Speaker 1: solar system. Pulsar planets endure intense radiation from rapidly spinning
1:49:04
Speaker 1: stellar corpses. Orbiting a pulsar means existing beside one of
1:49:09
Speaker 1: the harshest compact objects a planet can encounter. A pulsar
1:49:14
Speaker 1: produces beams of radiation and a powerful wind of energetic
1:49:17
Speaker 1: particles driven by its rotating magnetic field. Any nearby planet
1:49:22
Speaker 1: is therefore exposed to conditions completely unlike those around a
1:49:26
Speaker 1: calm main sequence star. The known pulsar system PSRB twelve
1:49:32
Speaker 1: fifty seven plus twelve contains several small planets whose precise
1:49:37
Speaker 1: gravitational influence can be detected through tiny changes in pulse
1:49:41
Speaker 1: arrival times. Their skies would receive no familiar, steady sunlight
1:49:46
Speaker 1: from the neutron star. Instead, the environment would be dominated
1:49:50
Speaker 1: by high energy radiation and a pulsar's rotational output. Researchers
1:49:56
Speaker 1: have explored whether sufficiently massive atmospheres might shield hypothetical planets
1:50:01
Speaker 1: in less extreme pulsar systems, but habitability remains highly speculative.
1:50:07
Speaker 1: The importance of these worlds lies elsewhere. They prove that
1:50:11
Speaker 1: planets can occupy environments astronomers once considered bizarre. A planetary
1:50:17
Speaker 1: system does not require a normal stellar host in order
1:50:20
Speaker 1: to remain gravitationally stable. Worlds can circle an object only
1:50:25
Speaker 1: kilometers across whose radio beam sweeps across the galaxy with
1:50:30
Speaker 1: extraordinary precision. Lava planets may possess oceans of molten rock
1:50:36
Speaker 1: and metal vapor. Place a rocky world close enough to
1:50:39
Speaker 1: its star, and the surface stops behaving anything like familiar geology.
1:50:45
Speaker 1: Some known exoplanets complete extremely tight orbits, where stellar heating
1:50:49
Speaker 1: can raise daytime temperatures beyond the melting points of common rocks.
1:50:54
Speaker 1: Their surfaces may contain broad regions of molten silicate above
1:50:59
Speaker 1: those reds uens. Vaporized rock can create a thin atmosphere
1:51:03
Speaker 1: containing substances such as sodium or silicon compounds rather than
1:51:09
Speaker 1: ordinary water vapor On a tidally locked world, one hemisphere
1:51:14
Speaker 1: may permanently face the star, while the opposite side remains
1:51:17
Speaker 1: much cooler. That enormous temperature difference could drive winds carrying
1:51:22
Speaker 1: vaporized material toward the night side. There, minerals might condense
1:51:27
Speaker 1: and return toward the surface before circulating again. Researchers model
1:51:32
Speaker 1: this as a kind of rock cycle, operating through evaporation
1:51:36
Speaker 1: rather than liquid water. Several ultra hot, rocky exoplanets are
1:51:41
Speaker 1: candidates for such environments. Observations of their thermal emission are
1:51:46
Speaker 1: beginning to test where the molten surfaces really exist. These
1:51:51
Speaker 1: planets take substances that form solid ground on Earth and
1:51:55
Speaker 1: place them into the role normally occupied by oceans and
1:51:58
Speaker 1: atmospheric gases. Familiar rock becomes weather. Carbon rich planets could
1:52:05
Speaker 1: hide vast interiors filled with crystalline diamond. The chemistry available
1:52:10
Speaker 1: when a planet forms can profoundly alter what grows inside it.
1:52:14
Speaker 1: Earth developed in a region where oxygen was abundant enough
1:52:17
Speaker 1: for silicate rock to dominate in a planetary system with
1:52:21
Speaker 1: a much higher carbon to oxygen ratio, different minerals could
1:52:25
Speaker 1: become important. Under immense internal pressure, carbon can adopt crystalline forms,
1:52:32
Speaker 1: including diamond. This inspired models of carbon rich planets containing
1:52:37
Speaker 1: thick layers of diamond surrounding metallic or carbadrichy interiors. The
1:52:42
Speaker 1: popular phrase diamond planet can be misleading because no astronomer
1:52:46
Speaker 1: has confirmed a world composed almost entirely of gemstone. Candidates
1:52:51
Speaker 1: once described that way remain uncertain because stellar chemistry and
1:52:56
Speaker 1: planetary composition are difficult to infer from afar. Even so,
1:53:02
Speaker 1: the underlying physics is real. Carbon subjected to suitable pressures
1:53:08
Speaker 1: can transform into diamond deep inside planets. Researchers also expect
1:53:14
Speaker 1: diamond formation within some giant ice planets through different chemical pathways.
1:53:20
Speaker 1: The possibility shows why exoplanet geology can differ radically from Earth's.
1:53:26
Speaker 1: Two rocky worlds with similar masses might possess entirely different
1:53:30
Speaker 1: interiors because their birth environment supplied different elemental ingredients. A
1:53:35
Speaker 1: planet's mineral structure can therefore record the chemistry of the
1:53:39
Speaker 1: disk from which it assembled. Cathonian planets may be exposed
1:53:43
Speaker 1: cares of vanished gas giants. A giant planet can migrate
1:53:48
Speaker 1: so close to its star that its enormous atmosphere begins
1:53:51
Speaker 1: to escape. Extreme radiation heats the upper layers and can
1:53:56
Speaker 1: drive gas away into space. If enough material is lost,
1:54:01
Speaker 1: the world may eventually resemble the dense core that once
1:54:05
Speaker 1: lay hidden beneath a much larger envelope. Astronomers sometimes call
1:54:09
Speaker 1: this hypothetical remnant a Cathonian planet. The name refers to
1:54:14
Speaker 1: the underworld in ancient Greek tradition, but the scientific idea
1:54:19
Speaker 1: concerns atmospheric destruction. Distinguishing an exposed giant planet core from
1:54:25
Speaker 1: an ordinary rocky planet is challenging because both could appear
1:54:28
Speaker 1: small and dense. Composition provides one clue. A stripped core
1:54:35
Speaker 1: might contain unusual proportions of heavy elements inherited from its
1:54:39
Speaker 1: former life inside a gas rich planet. Researchers have identified
1:54:43
Speaker 1: several extremely hot exoplanets as possible examples, but the evolutionary
1:54:49
Speaker 1: histories remain uncertain. The concept matters because planets do not
1:54:54
Speaker 1: keep their original forms forever. Stellar radiation can sculpt them
1:54:59
Speaker 1: across billions of years. A world observed today as a compact,
1:55:03
Speaker 1: rocky object might have begun as something resembling Neptune, before
1:55:08
Speaker 1: losing layer after layer of atmosphere until only its deepest
1:55:12
Speaker 1: interior remained. Some planets orbit stars that survived swallowing their
1:55:17
Speaker 1: earlier companions. Astronomers have found planets around stars whose histories
1:55:23
Speaker 1: may include stellar mergers or engulfment events. These systems can
1:55:28
Speaker 1: be difficult to reconstruct because the dramatic interaction happened long
1:55:32
Speaker 1: before we began observing them. One route begins inside a
1:55:36
Speaker 1: multiple star system. As stars evolved, Orbital changes can drive
1:55:41
Speaker 1: two of them together until one is swallowed by the other.
1:55:46
Speaker 1: A more distant planet may survive the disturbance and continue
1:55:49
Speaker 1: orbiting the merged star. In other scenarios, planets discovered around
1:55:54
Speaker 1: unusually massive evolved stars raise questions about whether the present
1:55:59
Speaker 1: host gained mass by consuming a companion. Chemical signatures and
1:56:04
Speaker 1: abnormal stellar rotation can preserve hints of such events. The
1:56:10
Speaker 1: situation shows how misleading a calm planetary system can be.
1:56:14
Speaker 1: A planet may appear to circle a single ordinary star today,
1:56:18
Speaker 1: while the star itself contains the combined material of two
1:56:22
Speaker 1: former suns. Surviving such a transformation would require the planet
1:56:27
Speaker 1: to remain far enough away to avoid destruction while its
1:56:30
Speaker 1: gravitational environment changed. These systems give astronomers a way to
1:56:35
Speaker 1: investigate the long term stability of planets when stellar evolution
1:56:39
Speaker 1: becomes far more complicated than the solitary life of our sun.
1:56:43
Speaker 1: Ultra short period planets complete entire years within a single
1:56:47
Speaker 1: Earth day. Some planets orbit so close to their stars
1:56:52
Speaker 1: that sunrise to sunrise comparisons become almost meaningless. Ultra short
1:56:57
Speaker 1: period planets finish a complete orbit in less than about
1:57:01
Speaker 1: one Earth day. Their stars dominate enormous portions of the
1:57:04
Speaker 1: sky from the planetary surface. Many of these worlds are rocky,
1:57:09
Speaker 1: and several appear denser than Earth, which may reflect the
1:57:12
Speaker 1: loss of volatile material under relentless heating. The orbital speed
1:57:17
Speaker 1: is extraordinary because gravity is much stronger at such small distances.
1:57:22
Speaker 1: A year can pass between breakfast and bedtime on Earth.
1:57:26
Speaker 1: Researchers are fascinated by how planets reach these orbits, because
1:57:30
Speaker 1: they probably did not all form exactly where we see
1:57:33
Speaker 1: them today. Gravitational interactions and tidal forces may gradually pull
1:57:39
Speaker 1: some worlds inward. Eventually, a planet can approach so close
1:57:44
Speaker 1: that the star begins distorting it. The strongest cases may
1:57:48
Speaker 1: be heading toward destruction as orbital energy dissipates. These systems
1:57:53
Speaker 1: let scientists study planetary survival at the very edge of
1:57:57
Speaker 1: what stable orbits permit. A world can remain recognizably planetary
1:58:02
Speaker 1: while traveling around its star hundreds of times during a
1:58:05
Speaker 1: single Earth year. Circumbinary planets experienced skies ruled by two
1:58:10
Speaker 1: moving suns planets really do, or big pairs of stars.
1:58:16
Speaker 1: In a circumbinary system, the two stars circle one another
1:58:20
Speaker 1: while the planet travels around both of them on a
1:58:22
Speaker 1: wider path. Astronomers once wondered whether such complicated gravitational environments
1:58:29
Speaker 1: could support stable planets at all. Discoveries by the Kepler
1:58:33
Speaker 1: Mission showed that they can. The geometry produces experiences impossible
1:58:38
Speaker 1: on Earth. From the planet, each sun would move relative
1:58:43
Speaker 1: to the other, equipses could alter the received starlight as
1:58:47
Speaker 1: one star passes in front of its partner. The changing
1:58:51
Speaker 1: stellar configuration also means astronomers cannot search for these planets
1:58:56
Speaker 1: using perfectly regular transits. Each crossing can occur at a
1:59:01
Speaker 1: slightly different time because the stars themselves are moving. That
1:59:06
Speaker 1: irregularity became one of the clues revealing the first systems
1:59:10
Speaker 1: thanet formation. Around binary stars also tests theories, because the
1:59:15
Speaker 1: young planetary disc must survive the gravitational influence of two
1:59:20
Speaker 1: central masses, yet nature repeatedly manages it. The fictional image
1:59:26
Speaker 1: of a world beneath two suns turned out not to
1:59:29
Speaker 1: require fictional physics. Real planets can spend every year orbiting
1:59:34
Speaker 1: a constantly moving stellar partnership. Exomoons may be common, although
1:59:39
Speaker 1: none has been confirmed beyond doubt. Moons are everywhere in
1:59:44
Speaker 1: our own Solar system, so astronomers expect many planets around
1:59:49
Speaker 1: other stars to possess them as well, Proving that expectation
1:59:53
Speaker 1: has been surprisingly difficult. An exomoon is far smaller than
1:59:58
Speaker 1: its planet and usually produces only a subtle additional signal.
2:00:03
Speaker 1: One strategy looks for tiny changes in when a planet
2:00:07
Speaker 1: crosses its star. A massive moon can tug the planet
2:00:11
Speaker 1: around their shared center of mass and shift the transit timing.
2:00:15
Speaker 1: The moon might also produce its own smaller dip in starlight.
2:00:20
Speaker 1: Several candidates have attracted considerable attention, including possible moons around
2:00:25
Speaker 1: giant planets discovered by the Kepler Mission. Follow Up studies
2:00:29
Speaker 1: have challenged or reinterpreted many of those signals. As a result,
2:00:34
Speaker 1: no exo moon currently enjoys the overwhelming conformation achieved for
2:00:39
Speaker 1: thousands of exopernits. Finding one would open an enormous new field.
2:00:45
Speaker 1: Large moons can influence planetary tides and axial stability. Some
2:00:50
Speaker 1: could even possess atmospheres or subsurface oceans of their own.
2:00:54
Speaker 1: Given how diverse moons are around nearby planets, the first
2:00:58
Speaker 1: secure detection beyond them the Solar System may reveal an
2:01:02
Speaker 1: object unlike anything astronomers originally expected to find. Trojan planets
2:01:07
Speaker 1: could share one orbit around the same star. Orbital mechanics
2:01:12
Speaker 1: allows two worlds to travel around a star at the
2:01:15
Speaker 1: same average distance without repeatedly colliding. The key is geometry.
2:01:22
Speaker 1: In a stable configuration, one planet can occupy a region
2:01:26
Speaker 1: roughly sixty degrees ahead of another along their shared orbit.
2:01:30
Speaker 1: A second stable region lies the same angle behind. These
2:01:36
Speaker 1: locations are associated with gravitational balance points known as lagrange points.
2:01:41
Speaker 1: Our Solar System already demonstrates the principle with swarms of
2:01:45
Speaker 1: Trojan asteroids sharing Jupiter's orbit. Extending the idea to two
2:01:50
Speaker 1: planet sized bodies produces a fascinating possibility called co orbital
2:01:55
Speaker 1: or trojan planets. Simulations show that such arrangements can survive
2:02:01
Speaker 1: under suitable conditions. Astronomers have searched for evidence through transit
2:02:06
Speaker 1: timing and other orbital measurements. There have been intriguing candidates,
2:02:11
Speaker 1: but secure examples of two full sized planets locked in
2:02:14
Speaker 1: a classic trojan configuration remain elusive. Confirming one would broaden
2:02:20
Speaker 1: the meaning of a planetary orbit. We naturally imagine each
2:02:24
Speaker 1: planet occupying its own separate track around a star. Gravity
2:02:29
Speaker 1: allows something stranger. Two substantial worlds could keep the same
2:02:34
Speaker 1: year and follow the same orbital path while permanently remaining
2:02:38
Speaker 1: separated by a stable angular distance. Rogue moons may wander
2:02:43
Speaker 1: between stars after escaping their planetary systems. A moon normally
2:02:48
Speaker 1: seems inseparable from its planet, but gravitational chaos can break
2:02:53
Speaker 1: that relationship completely. During the violent early history of a
2:02:57
Speaker 1: planetary system, giant worlds can scatter one another into new orbits.
2:03:03
Speaker 1: Close encounters can also strip moons away from their hosts.
2:03:08
Speaker 1: The liberated moon might be captured elsewhere, crash into another object,
2:03:13
Speaker 1: or escape the entire system and enter interstellar space alone.
2:03:18
Speaker 1: Researchers sometimes call these objects nomadic moons or rogue exo moons.
2:03:24
Speaker 1: Detecting one would be exceptionally difficult, because a small world
2:03:28
Speaker 1: without a nearby star reflects almost no light. Young examples
2:03:33
Speaker 1: could retain enough internal heat to glow faintly in infrared wavelengths.
2:03:38
Speaker 1: Others might carry thick atmospheres that slow the loss of warmth.
2:03:42
Speaker 1: A large moon could even preserve subsurface liquid through radioactive
2:03:46
Speaker 1: heating long after leaving its parent planet. None has been
2:03:51
Speaker 1: securely identified drifting independently between stars, yet, computer simulations show
2:03:57
Speaker 1: that planetary systems can eject enormal amounts of material somewhere
2:04:02
Speaker 1: in the darkness. Objects that began life watching a giant
2:04:06
Speaker 1: planet fill their sky may now be traveling through the
2:04:09
Speaker 1: galaxy with no planet or sun beside them. A few
2:04:14
Speaker 1: asteroids travel through space from completely different star systems. For
2:04:18
Speaker 1: most of astronomical history, every small object seen passing through
2:04:23
Speaker 1: the Solar System was assumed to belong here. That changed
2:04:27
Speaker 1: when Umormor was discovered in twenty seventeen. Its trajectory was
2:04:33
Speaker 1: unmistakably hyperbolic, which meant the sum could bend its path
2:04:37
Speaker 1: but could never hold it permanently. The object had arrived
2:04:41
Speaker 1: from interstellar space. Its brightness changed dramatically as it rotated
2:04:47
Speaker 1: suggesting an unusually elongated or flattened shape. Astronomers also detected
2:04:53
Speaker 1: a slight acceleration that could not be explained by gravity alone.
2:04:58
Speaker 1: Although no obvious cometary cloud was seen around it, proposed
2:05:02
Speaker 1: explanations ranged from subtle outgassing to unusual surface properties. Whatever
2:05:08
Speaker 1: its exact nature, its origin beyond our system is clear.
2:05:13
Speaker 1: Since then, astronomers have become increasingly aware that material exchanged
2:05:18
Speaker 1: between planetary systems should be a normal consequence of planet formation.
2:05:23
Speaker 1: Giant planets can fling asteroids outward until they escape their
2:05:27
Speaker 1: home stars forever. Those fragments can then spend millions of
2:05:32
Speaker 1: years crossing the galaxy. Amoremor showed that one can eventually
2:05:36
Speaker 1: pass close enough for humanity to notice, bringing physical material
2:05:40
Speaker 1: from another planetary system directly through our celestial neighborhood. Interstellar
2:05:46
Speaker 1: comets preserve material formed around distant unknown suns. The discovery
2:05:51
Speaker 1: of comet Borisov in two thousand nineteen gave astronomers something unprecedented.
2:05:58
Speaker 1: Unlike Umu mur, this interstellar visitor clearly behaved like a comet.
2:06:04
Speaker 1: Sunlight warmed its surface and released gas and dust, producing
2:06:09
Speaker 1: a recognizable coma and tail. Its orbit showed that it
2:06:13
Speaker 1: had entered the Solar System from beyond the Sun's gravitational
2:06:16
Speaker 1: domain and would leave permanently. That meant astronomers could analyze
2:06:22
Speaker 1: matter that formed around another star without traveling anywhere. Spectrostoby
2:06:27
Speaker 1: revealed familiar cometary ingredients, but some chemical proportions differed from
2:06:32
Speaker 1: typical Solar System comets. Borisov appeared unusually rich in carbon
2:06:38
Speaker 1: monoxide during part of its passage that may hinted formation
2:06:43
Speaker 1: in a colder region around its original star, or around
2:06:46
Speaker 1: a star with conditions different from those surrounding the young Sun.
2:06:51
Speaker 1: The comet's home system is unknown because gravitational encounters over
2:06:55
Speaker 1: immense stretches of time make its path difficult to trace
2:06:59
Speaker 1: backward with certainty. Its importance lies in what survived the journey.
2:07:05
Speaker 1: Frozen material assembled around a distant star remained preserved during
2:07:09
Speaker 1: an interstellar crossing, then briefly warmed to near our Sun
2:07:13
Speaker 1: and released molecules that telescopes on Earth could examine. Active
2:07:17
Speaker 1: asteroids grow comet like tails despite orbiting within the asteroid belt.
2:07:23
Speaker 1: The boundary between asteroid and comet turned out to be
2:07:25
Speaker 1: less tidy than astronomers once imagined. Some objects travel on
2:07:30
Speaker 1: ordinary asteroid like orbits, yet suddenly developed tails or dusty clouds.
2:07:36
Speaker 1: These are known as active asteroids. Several different processes can
2:07:42
Speaker 1: produce the effect. A collision may blast surface material into space.
2:07:47
Speaker 1: Rapid routation can weaken the object until dust slides or
2:07:51
Speaker 1: breaks away. Thermal cracking can also release particles after repeated heating.
2:07:57
Speaker 1: In other cases, buried ice may turn directly into gas
2:08:02
Speaker 1: and drag dust from the surface. Because identical appearances can
2:08:06
Speaker 1: arise through very different mechanisms, each active asteroid becomes a
2:08:11
Speaker 1: small detective story. Astronomer's track how long the activity lasts,
2:08:16
Speaker 1: and whether it returns at the same part of the orbit.
2:08:20
Speaker 1: Repeated activity near the Sun can point towards sublimating ice
2:08:24
Speaker 1: rather than a single impact. These objects matter because they
2:08:28
Speaker 1: reveal that the asteroid belt is not simply a collection
2:08:31
Speaker 1: of inert rocks. Small bodies continue to collide and fracture
2:08:36
Speaker 1: there today. Some even retain volatile material after billions of years.
2:08:42
Speaker 1: The tail does not automatically make an object a traditional comet.
2:08:46
Speaker 1: Sometimes an asteroid can temporarily imitate one. Centaurs behave partly
2:08:51
Speaker 1: like asteroids and partly like unstable comets. Between Jupiter and
2:08:58
Speaker 1: Neptune lives a population of sars, small bodies whose futures
2:09:01
Speaker 1: are unusually uncertain. They are called centaurs because their behaviour
2:09:07
Speaker 1: seems divided between two familiar categories. Their orbits resemble those
2:09:13
Speaker 1: of asteroids in some respects, yet many contain volatile material
2:09:17
Speaker 1: and can develop comet like activity when sufficiently heated. More importantly,
2:09:23
Speaker 1: the giant planets constantly disturb their paths. A close encounter
2:09:28
Speaker 1: with Saturn or another massive world can dramatically alter a
2:09:33
Speaker 1: centaur's orbit. Over astronomical time scales, many are expected to
2:09:38
Speaker 1: be thrown outward, sent inward toward the Sun, or ejected
2:09:42
Speaker 1: from the Solar System entirely. Some may eventually become short
2:09:46
Speaker 1: period comets. The best known example is Chiron. It was
2:09:52
Speaker 1: initially classified as an asteroid before astronomers detected a surrounding
2:09:56
Speaker 1: coma revealing active material escaping from its surface. Other centaurs
2:10:02
Speaker 1: possess rings or unexpected color variations that add to the
2:10:06
Speaker 1: diversity of the group. Their unstable location makes them temporary
2:10:11
Speaker 1: residents of the region they occupy. They are travelers caught
2:10:15
Speaker 1: between the distant reservoir of icy bodies and the warmer
2:10:18
Speaker 1: inner solar system. Watching them allows astronomers to study small
2:10:23
Speaker 1: worlds while their orbits are actively being rewritten by giant planets.
2:10:29
Speaker 1: Contact binaries are two small worlds gently joined together. Some
2:10:34
Speaker 1: objects that look like single, oddly shaped bodies are actually
2:10:38
Speaker 1: two separate lobes touching at a narrow neck. This structure
2:10:42
Speaker 1: is called a contact binary. Arakoth provided a spectacular example
2:10:49
Speaker 1: when the New Horizon spacecraft flew past it in two
2:10:52
Speaker 1: thousand nineteen. The distant object consists of two flattened comperments
2:10:58
Speaker 1: joined together. Their remarkably undisturbed appearance suggests they did not
2:11:02
Speaker 1: smash into one another at high speed. Instead, the pieces
2:11:07
Speaker 1: may have formed nearby within the Young Solar System and
2:11:11
Speaker 1: gradually lost orbital energy until they came together slowly. That
2:11:15
Speaker 1: makes Arikov a valuable record of how planetesimals assembled. A
2:11:20
Speaker 1: violent collision would have shattered or heavily deformed the components,
2:11:25
Speaker 1: their survival points toward a much gentler meeting. Similar double
2:11:29
Speaker 1: lobed shapes appear among comets and asteroids, although not every
2:11:33
Speaker 1: example must share exactly the same history. Contact binaries challenge
2:11:38
Speaker 1: the instinct to imagining planetary formation as constant high speed
2:11:42
Speaker 1: impact at least some building box may have approached one
2:11:46
Speaker 1: another gradually enough to remain recognizable after joining. A world
2:11:51
Speaker 1: can therefore be assembled from two former companions whose final
2:11:55
Speaker 1: orbital motion ended not with destruction but with permanent concon
2:12:01
Speaker 1: Metal rich asteroids may be fragments of shattered planetary cores.
2:12:06
Speaker 1: When the Young Solar System was crowded with growing worlds,
2:12:10
Speaker 1: some small bodies became hot enough for their interiors to
2:12:14
Speaker 1: separate into layers. Dens iron and nickel sank toward their centres,
2:12:19
Speaker 1: while lighter rock moved upward. These differentiated objects were essentially
2:12:24
Speaker 1: miniature planets with metallic cores. Many were later destroyed by collisions.
2:12:30
Speaker 1: If a catastrophic impact stripped away the rocky exterior, pieces
2:12:34
Speaker 1: of the exposed core could survive as metal rich asteroids.
2:12:39
Speaker 1: The asteroid Psyche has attracted enormous interest because radar observations
2:12:44
Speaker 1: and measurements of its density suggest that metal is an
2:12:47
Speaker 1: important part of its composition. Scientists once imagined it might
2:12:52
Speaker 1: be an almost completely exposed planetary core. More recent evidence
2:12:57
Speaker 1: points toward a complicated mixture of metal and rock, making
2:13:01
Speaker 1: its true history even more interesting. A spacecraft is traveling
2:13:06
Speaker 1: to investigate it. Directly studying such objects could reveal processes
2:13:11
Speaker 1: normally hidden thousands of kilometers beneath pernitory surfaces. Earth's core
2:13:17
Speaker 1: is inaccessible to direct exploration, but a shattered protoplanet may
2:13:22
Speaker 1: have scattered comparable material into space, and metallic asteroid can
2:13:27
Speaker 1: therefore function as a surviving fragment from the internal anatomy
2:13:30
Speaker 1: of a world that ceased to exist billions of years ago.
2:13:34
Speaker 1: Mine belt comets contain ancient ice in unexpectedly warm regions.
2:13:40
Speaker 1: Ice is usually associated with the cold outer Solar System,
2:13:44
Speaker 1: far beyond the orbit of Jupiter. Yet astronomers have found
2:13:48
Speaker 1: objects within the main asteroid belt that repeatedly released dust
2:13:52
Speaker 1: and away, consistent with buried ice turning into gas. These
2:13:57
Speaker 1: bodies are called main belt comets. Their existence was surprising
2:14:02
Speaker 1: because they have spent immense periods much closer to the
2:14:05
Speaker 1: Sun than ordinary comets. Surface ice exposed for billions of
2:14:09
Speaker 1: years should disappear, the solution may lie underground. A protective
2:14:15
Speaker 1: layer of dust and rock can insulate ice and allowed
2:14:19
Speaker 1: to survive at depth. A small landslide or impact can
2:14:24
Speaker 1: expose a fresh patch, allowing sunlight to trigger temporary activity.
2:14:29
Speaker 1: These objects have important implications for the history of water
2:14:33
Speaker 1: in the Inner Solar System. Icy bodies from the asteroid
2:14:36
Speaker 1: region may have contributed some water to the young terrestrial
2:14:39
Speaker 1: planets during repeated impacts. Mang Bald comets also show that
2:14:44
Speaker 1: the early Solar System did not divide cleanly into rocky
2:14:47
Speaker 1: material near the Sun and icy material farther away. Ancient
2:14:52
Speaker 1: volatile substances can survive in places where their presence was
2:14:56
Speaker 1: once considered unlikely. Protected beneath dark cellar for enormous stretches
2:15:01
Speaker 1: of time, some comets become visible only once before leaving
2:15:06
Speaker 1: the Sun forever. Most familiar comets either return periodically or
2:15:11
Speaker 1: remain gravitationally bound on extremely long orbits. Hyperbolic comets follow
2:15:17
Speaker 1: a different destiny. If an object reaches the Inner Solar
2:15:21
Speaker 1: System with enough energy, its path around the Sun remains open,
2:15:25
Speaker 1: rather than closing into an ellipse. After passing perihelion, it
2:15:30
Speaker 1: travels outward without returning. Some began inside our own system
2:15:35
Speaker 1: and gained escape velocity through a close encounter with a
2:15:38
Speaker 1: giant planet. Others can receive a smaller gravitational change after
2:15:43
Speaker 1: approaching the Sun on an orbit already close to the
2:15:46
Speaker 1: escape boundary. Interstellar visitors represent the most extreme examples because
2:15:52
Speaker 1: they were never bound to the Sun in the first place.
2:15:55
Speaker 1: For observers, this creates a unique encounter. Humanity may have
2:16:01
Speaker 1: only one opportunity to study the object before it disappears
2:16:05
Speaker 1: permanently into deep space. There will be no return apparition
2:16:10
Speaker 1: for future astronomers with better instruments, Measurements must be made
2:16:14
Speaker 1: during their brief passage, every spectrum and image becomes irreplaceable.
2:16:20
Speaker 1: Comets are often described as recurring celestial visitors, but some
2:16:25
Speaker 1: are more accurately cosmic departures. We see them during the
2:16:29
Speaker 1: single moment when their paths cross the Inner Solar System
2:16:33
Speaker 1: before they continue outward without another scheduled meeting. Sedna follows
2:16:38
Speaker 1: an orbit so distant its origin remains uncertain. Sedna spends
2:16:43
Speaker 1: most of its extraordinary journey far beyond the familiar planets.
2:16:47
Speaker 1: Even at its closest approach, it remains roughly twice as
2:16:50
Speaker 1: far from the Sun as Neptune. At the distant end
2:16:54
Speaker 1: of its orbit, it travels hundreds of times farther from
2:16:57
Speaker 1: the Sun than Earth does. Completing one revolution takes more
2:17:01
Speaker 1: than ten thousand years. The real mystery is how Sedna
2:17:06
Speaker 1: acquired such an elongated path, Neptune is too distant from
2:17:10
Speaker 1: it to provide the necessary gravitational kick under present conditions.
2:17:15
Speaker 1: One possibility reaches back to the Sun's birth cluster. A
2:17:19
Speaker 1: neighbouring star may have passed close enough to disturb Sedna
2:17:23
Speaker 1: while the Solar System was still young. Another explanation involves
2:17:28
Speaker 1: gravitational effects from an undiscovered distant planet. Sedna might also
2:17:33
Speaker 1: represent the inner edge of the Aught Cloud, although its
2:17:37
Speaker 1: relationship to that enormous hypothetical reservoir remains uncertain. Only a
2:17:43
Speaker 1: small number of objects with somewhat similar extreme orbits are known.
2:17:48
Speaker 1: Each new discovery helps test the competing ideas Sedna is
2:17:53
Speaker 1: not interesting merely because it travels far away. Its orbit
2:17:57
Speaker 1: appears to preserve evidence of an event or gravitational influence
2:18:01
Speaker 1: that astronomers have not yet conclusively identified. Antimatter is abundant
2:18:06
Speaker 1: in laboratories but exceptionally scarce throughout ordinary space. Every known
2:18:12
Speaker 1: particle has an antimatter counterpart with the same mass but
2:18:15
Speaker 1: opposite electrical properties. Where charge applies. When matter and antimatter meat,
2:18:21
Speaker 1: they can annihilate and convert their mass into other forms
2:18:24
Speaker 1: of energy. Physicists routinely create antiparticles in accelerators, and positrons
2:18:30
Speaker 1: are also produced naturally in certain radioactive decays and energetic
2:18:35
Speaker 1: astrophysical processes. The deeper puzzle is why the observable universe
2:18:40
Speaker 1: is overwhelmingly built from matter. The early universe should have
2:18:44
Speaker 1: produced matter and antimatter in nearly equal amounts. According to
2:18:49
Speaker 1: simple expectations. If perfect balance had persisted, almost everything would
2:18:54
Speaker 1: have annihilated. Instead, a tiny excess of matter apparently survived,
2:18:59
Speaker 1: and if ventrally formed galaxies, planets, and people. Experiments study
2:19:04
Speaker 1: subtle differences in the behavior of particles and antiparticles in
2:19:09
Speaker 1: search of an explanation. Large regions made from antimatter are
2:19:14
Speaker 1: considered unlikely because boundaries where they encountered normal matter should
2:19:19
Speaker 1: produce distinctive gamma radiation. None has been established. Antimatter itself
2:19:26
Speaker 1: is therefore not mythical or impossibly rare we manufacture it.
2:19:31
Speaker 1: What remains astonishingly rare is antimatter assembled into enduring, large
2:19:36
Speaker 1: scale structures. The cosmos somehow chose matter overwhelmingly, and physicists
2:19:42
Speaker 1: still do not completely understand why strangelets could be tiny
2:19:47
Speaker 1: stable fragments of hypothetical quark matter. Ordinary atomic nuclei are
2:19:53
Speaker 1: belt from protons and neutrons. Each of those particles is
2:19:58
Speaker 1: itself made from quark. At sufficiently extreme densities, theorists have
2:20:04
Speaker 1: explored whether quarks could exist together in larger collections without
2:20:08
Speaker 1: remaining confined inside individual nucleons. One proposed form is strange
2:20:15
Speaker 1: quark matter, which would contain up, down, and strange quarks.
2:20:20
Speaker 1: A small stable fragment of this material is called a strangelet.
2:20:26
Speaker 1: No strangehert has been confirmed. Physicists have searched for them
2:20:31
Speaker 1: in cosmic rays and particle collisions, because discovering one would
2:20:36
Speaker 1: reveal an entirely new stable form of matter. Theoretical predictions
2:20:41
Speaker 1: vary enormously. Strange hurts might be unstable and disappear almost immediately,
2:20:47
Speaker 1: or certain combinations could persist under suitable conditions. Neutron star
2:20:52
Speaker 1: collisions have been suggested as one possible natural source if
2:20:56
Speaker 1: strange matter exists inside compact star. Safety concerns sometimes appear
2:21:03
Speaker 1: in popular discussions of strangelets, but collider experiments have not
2:21:07
Speaker 1: produced evidence of dangerous self growing matter. Their real scientific
2:21:12
Speaker 1: importance is more fundamental. A confirmed strange lit would show
2:21:16
Speaker 1: that familiar nuclei are not the only possible long lived
2:21:20
Speaker 1: arrangements of quarks. Nature may possess an additional category of
2:21:25
Speaker 1: matter that ordinary planets almost never encounter. Magnetic monopoles are
2:21:30
Speaker 1: predicted particles, but nobody has conclusively detected. Cut an ordinary
2:21:35
Speaker 1: bar magnet in half, and each piece still has both
2:21:38
Speaker 1: a north and south pole. No matter how often the
2:21:41
Speaker 1: process is repeated, an isolated magnetic pole never appears. Some
2:21:47
Speaker 1: theories of particle physics predict that truly fundamental particles carrying
2:21:52
Speaker 1: a single magnetic charge could nevertheless exist. These hypothetical objects
2:21:57
Speaker 1: are called magnetic monopole. Their discovery would be profound because
2:22:03
Speaker 1: it could explain why electric charge occurs in discrete units
2:22:07
Speaker 1: and provide evidence for attempts to unify fundamental forces. Certain
2:22:13
Speaker 1: grand unified theories suggest monopoles may have formed during extremely
2:22:17
Speaker 1: early cosmic phase transitions. Inflation could then have diluted their
2:22:22
Speaker 1: abundance so dramatically that finding one today became extraordinarily unlikely.
2:22:28
Speaker 1: Experiments have searched through particle detector data and even examined
2:22:33
Speaker 1: unusual materials for trapped monopoles. There have been intriguing events,
2:22:38
Speaker 1: but no result has achieved. Convincing confirmation. A monopole would
2:22:43
Speaker 1: behave unlike any ordinary magnet, because it could possess a
2:22:47
Speaker 1: north pole without a corresponding south pole or the reverse.
2:22:52
Speaker 1: The concept is mathematically elegant enough that physicists have searched
2:22:56
Speaker 1: for decades. Nature has simply refused so far to reveal
2:23:01
Speaker 1: whether the particle exists outside the equations. Actions may be
2:23:06
Speaker 1: incredibly like particles filling the universe. Unseen dark matter outweighs
2:23:12
Speaker 1: the ordinary matter that forms stars and planets, yet its
2:23:16
Speaker 1: microscopic identity remains unknown. Actions are among the most intriguing candidates.
2:23:22
Speaker 1: They were originally proposed to solve an unrelated puzzle involving
2:23:26
Speaker 1: the strong nuclear force. Physicists then realized that enormous numbers
2:23:32
Speaker 1: of very light actions produced in the early universe could
2:23:36
Speaker 1: also behave as cold dark matter. An individual action might
2:23:40
Speaker 1: possess o mere tiny fraction of an electron's mask, but
2:23:43
Speaker 1: the collective population could still exert the gravity required to
2:23:46
Speaker 1: shape galaxies. Detecting them is extremely difficult because their interactions
2:23:52
Speaker 1: with normal matter would be extraordinarily weak. Some experiments use
2:23:56
Speaker 1: intense magnetic fields and exquisitely sensitive electronics to search for
2:24:01
Speaker 1: the possibility that an action converts into a photon. Others
2:24:06
Speaker 1: look toward the Sun, where action like particles might potentially
2:24:10
Speaker 1: be produced in the hot interior. No experiment has confirmed them.
2:24:15
Speaker 1: The appeal of the idea lies in its efficiency. One
2:24:19
Speaker 1: hypothetical particle could connect a problem in nuclear physics with
2:24:22
Speaker 1: the astronomical mystery of invisible mass. If actions exist, the
2:24:28
Speaker 1: space around you could contain vast numbers of them passing
2:24:32
Speaker 1: unnoticed through Earth. At this very moment, sterile neutrinos could
2:24:37
Speaker 1: exist without feeling most known forces. The three known types
2:24:41
Speaker 1: of neutrinos are already remarkably elusive. They ignore the electromagnetic
2:24:47
Speaker 1: force and interact through the weak nuclear force as well
2:24:50
Speaker 1: as gravity. A proposed sterile neutrino would go further. It
2:24:55
Speaker 1: would not participate directly in the weak force at all.
2:25:00
Speaker 1: Scientists could detect it only indirectly if it mixed with
2:25:03
Speaker 1: ordinary neutrinos or influenced other measurable processes. The idea emerged
2:25:09
Speaker 1: partly because neutrinos possess mass, which requires physics beyond the
2:25:14
Speaker 1: simplest original version of the standard model. Sterile neutrinos have
2:25:19
Speaker 1: also been proposed as possible contributors to dark matter, depending
2:25:23
Speaker 1: on their mass. Several experiments have reported anomalies that inspired
2:25:28
Speaker 1: interest in additional neutrino states, but results from different detectors
2:25:32
Speaker 1: have not produced a consistent discovery. Searches continue using nuclear reactors,
2:25:39
Speaker 1: particle accelerators, and astronomical observations. The name sterile does not
2:25:45
Speaker 1: mean chemically inert. It describes the particle's extraordinary isolation from
2:25:51
Speaker 1: familiar interactions. If such neutrinos exist, entire populations could have
2:25:57
Speaker 1: crossed the universe while barely acknowledging ordinary matter. Discovering one
2:26:02
Speaker 1: would enlarge the known neutrino family and reveal a particle
2:26:06
Speaker 1: that lives even farther outside everyday physics than the already
2:26:10
Speaker 1: ghost like neutrinos we know. Ultra high energy cosmic rays
2:26:15
Speaker 1: arrive with energies that remain difficult to explain. Every so often,
2:26:20
Speaker 1: Earth's atmosphere is struck by a subatomic particle carrying an
2:26:24
Speaker 1: almost ridiculous amount of energy. The most extreme cosmic rays
2:26:28
Speaker 1: can possess the kinetic energy of a well hit tennis
2:26:31
Speaker 1: bore concentrated into a single atomic nucleus or proton. When
2:26:36
Speaker 1: one enters the atmosphere, it collides with molecules and produces
2:26:40
Speaker 1: a vast cascade of secondary particles that spreads across kilometers
2:26:46
Speaker 1: ground based observatories. We construct the original event from this shower.
2:26:51
Speaker 1: The mystery is where such particles are accelerated. Ordinary stellar
2:26:56
Speaker 1: processes struggle to reach the required energies. Candidate sources include
2:27:01
Speaker 1: powerful jets from active galaxies and other environments containing enormous
2:27:06
Speaker 1: magnetic fields. Yet, charged particles do not travel straight through
2:27:11
Speaker 1: space because galactic and intergalactic magnetism bends their trajectories. That
2:27:17
Speaker 1: makes tracing them back to their origins extremely difficult. The
2:27:22
Speaker 1: highest energy examples also interact with background radiation during long journeys,
2:27:27
Speaker 1: which limits how far they can travel before losing energy.
2:27:31
Speaker 1: Their very arrival therefore implies that sufficiently powerful accelerators exist
2:27:36
Speaker 1: somewhere within the accessible cosmic neighborhood. Nature is launching individual
2:27:42
Speaker 1: particles at energy's Human made accelerators cannot remotely approach, and
2:27:46
Speaker 1: the exact machines responsible remain uncertain. Some atomic nuclei survive
2:27:52
Speaker 1: journeys across space at nearly light speed. Cosmic rays are
2:27:57
Speaker 1: not rays of light. Many are actual pieces of atoms
2:28:02
Speaker 1: stripped of their electrons and accelerated to enormous speeds. Protons dominate,
2:28:08
Speaker 1: but detectors also find nuclei ranging from helium to iron
2:28:12
Speaker 1: and beyond. These particles can spend immense periods traveling through
2:28:17
Speaker 1: magnetic fields before eventually colliding with Earth's atmosphere. A heavy
2:28:22
Speaker 1: nucleus moving close to light speed experiences conditions far removed
2:28:26
Speaker 1: from anything in an ordinary atom. Its electrons are gone,
2:28:30
Speaker 1: yet its protons and neutrons remain bound together, while the
2:28:34
Speaker 1: entire nucleus carries extraordinary kinetic energy. Where the different species
2:28:40
Speaker 1: originate is an active field of research. Supernova remnants can
2:28:45
Speaker 1: accelerate many lower energy cosmic rays through shock waves. More
2:28:49
Speaker 1: energetic particles may require larger or more powerful environments. By
2:28:55
Speaker 1: measuring the proportions of different nuclei and their energies, researchers
2:28:59
Speaker 1: can infer ifer something about their sources and what happened
2:29:02
Speaker 1: during the journey. Some unstable isotopes can even function as
2:29:07
Speaker 1: cosmic clocks because their decay constrains travel times. A fragment
2:29:13
Speaker 1: of an atomic nucleus can therefore cross interstellar space for
2:29:17
Speaker 1: ages before striking our atmosphere and revealing clues about remote
2:29:21
Speaker 1: astrophysical accelerators. Positronium forms briefly. When matter binds directly with antimatter,
2:29:29
Speaker 1: An electron and its antimatter counterpart can do something remarkable
2:29:33
Speaker 1: before they destroy one another. Instead of annihilating immediately, the
2:29:38
Speaker 1: negatively charged electron can orbit together with the positively charged
2:29:43
Speaker 1: positron and form an exotic atom called positronium. No proton
2:29:49
Speaker 1: or neutron is required. The two particles have equal mass,
2:29:53
Speaker 1: so they orbit their shared center very differently from an
2:29:56
Speaker 1: electron moving around a heavy atomic nucleus. Positronium survives only
2:30:02
Speaker 1: briefly because its components eventually annihilate and produce photons. The
2:30:07
Speaker 1: exact lifetime depends on how their spins are arranged. Despite
2:30:11
Speaker 1: its fleeting existence, physicists can create positronium in laboratories and
2:30:16
Speaker 1: use it for extremely precise tests of quantum electrodynamics. Researchers
2:30:21
Speaker 1: have even produced excited forms and are investigating where the
2:30:25
Speaker 1: collections of positronium can be manipulated for more elaborate experiments.
2:30:31
Speaker 1: The system provides perhaps the cleanest possible meeting between matter
2:30:35
Speaker 1: and antimatter. They do not simply collide at random. For
2:30:39
Speaker 1: a tiny interval, they form a genuine bound structure with
2:30:43
Speaker 1: measurable energy levels. An atom can therefore exist without any
2:30:48
Speaker 1: conventional nucleus and contain equal amounts of matter and antimatter
2:30:53
Speaker 1: right up until the moment both disappear into radiation. Wollonium
2:30:58
Speaker 1: is an exotic atom built without any ordinary atomic nucleus.
2:31:03
Speaker 1: Replace the proton in hydrogen with a positively charged antimuon,
2:31:08
Speaker 1: and a strange but genuine atom appears. It is called muonium.
2:31:14
Speaker 1: An electron orbits the anti moon. Because the two particles
2:31:18
Speaker 1: carry opposite electric charges. Unlike an ordinary nucleus, the antimuine
2:31:23
Speaker 1: is considered an elementary particle rather than a composite object
2:31:27
Speaker 1: made from Quarksmuonium therefore gives physicists an exceptionally clean system
2:31:33
Speaker 1: for testing fundamental theories. It lasts only as long as
2:31:37
Speaker 1: its anti muin survives, which is a little over two
2:31:40
Speaker 1: millionths of a second on average. That tiny window is
2:31:44
Speaker 1: enough for precision experiments. Scientists measure its energy levels and
2:31:49
Speaker 1: magnetic behavior to compare them with predictions from quantum electrodynamics.
2:31:55
Speaker 1: Researchers are also searching for an astonishing transformation in which
2:31:59
Speaker 1: moorn could spontaneously become antimomonium, observing that would violate familiar
2:32:06
Speaker 1: conservation rules and signal new physics. Despite its name, muonium
2:32:12
Speaker 1: contains no muon in the usual negative form. The positive
2:32:17
Speaker 1: antimuon takes the central role. For a few microseconds, Nature
2:32:23
Speaker 1: constructs an atom with no proton or neutron at all,
2:32:26
Speaker 1: using an unstable elementary particle as the anchor around which
2:32:30
Speaker 1: an electron moves. Ridberg matter contains atoms expanded to extraordinary
2:32:36
Speaker 1: sizes by excited electrons. An ordinary atom is already mostly
2:32:41
Speaker 1: empty space, but a Ridberg atom pushes that idea to
2:32:45
Speaker 1: an extraordinary extreme. One electron is promoted into a state
2:32:50
Speaker 1: with very high energy. Its typical distance from the nucleus
2:32:55
Speaker 1: can then become hundreds or thousands of times greater than
2:32:58
Speaker 1: in the atom's normal Collections of highly excited atoms can
2:33:03
Speaker 1: sometimes interact to form unusual condensed states described as rid
2:33:08
Speaker 1: Bird matter. Their exaggerated dimensions give them remarkable electrical properties
2:33:14
Speaker 1: and make neighbouring atoms extraordinarily sensitive to one another. Even
2:33:19
Speaker 1: weak external fields can dramatically affect them. Physicists exploit these
2:33:25
Speaker 1: characteristics in experiments involving quantum information and precision sensing. Individual
2:33:31
Speaker 1: Rieberg atoms can be arranged with lasers and made to
2:33:34
Speaker 1: control where the nearby atoms become excited. This creates a
2:33:39
Speaker 1: phenomenon called ride Berg blockade that can act like a
2:33:43
Speaker 1: switch between quantum states. The atoms are not permanently enormous,
2:33:50
Speaker 1: their excited configurations eventually decay and release energy for the
2:33:55
Speaker 1: period in which they survive. However, the scale of the
2:33:59
Speaker 1: electronic orbit is transformed. Quantum mechanics can take a microscopic
2:34:04
Speaker 1: atom and temporarily expand one part of its structure toward
2:34:08
Speaker 1: dimensions that begin to approach the nanoscale world. Natural nuclear
2:34:13
Speaker 1: reactors once operated inside ancient uranium deposits on Earth. More
2:34:18
Speaker 1: than one and a half billion years before humans built
2:34:21
Speaker 1: a reactor, Nature assembled several of its own beneath what
2:34:25
Speaker 1: is now Gabon in Central Africa. The phenomenon was discovered
2:34:29
Speaker 1: at Oaklo when scientists noticed that uranium ore contained slightly
2:34:33
Speaker 1: unusual isotope ratios. The explanation was extraordinary. Roughly two billion
2:34:40
Speaker 1: years ago, natural uranium contained a larger fraction of uranium
2:34:44
Speaker 1: two thirty five than it does today in certain rich
2:34:48
Speaker 1: deposits ground water entered cracks in the ore and slowed
2:34:53
Speaker 1: neutrons enough to sustain nuclear fission. As the reaction heated
2:34:57
Speaker 1: the water, some boiled or moved all away and reduced
2:35:01
Speaker 1: the neutron moderation. The reactor then weakened until water returned.
2:35:06
Speaker 1: This created a natural, self regulating cycle. The reactions continued
2:35:12
Speaker 1: intermittently over immense periods and produced many of the same
2:35:16
Speaker 1: kinds of fission products associated with engineered reactors. Their remains
2:35:21
Speaker 1: have helped scientists study how radioactive elements migrate through geological
2:35:25
Speaker 1: material across enormous spans of time. Ochlod demonstrates that nuclear
2:35:31
Speaker 1: technology relies on physical conditions. Nature can occasionally assemble unaided.
2:35:37
Speaker 1: Long before any creature understood the atom, ground water and
2:35:42
Speaker 1: uranium combined underground to create sustained nuclear chain reactions. Helium
2:35:49
Speaker 1: hydride was probably the universe's first molecular bond. Before stars existed,
2:35:55
Speaker 1: The young universe had to make chemistry from an extremely
2:35:58
Speaker 1: limited collection of ingredients. Hydrogen and helium dominated. After the
2:36:03
Speaker 1: cosmos cooled enough for atomic nuclei to capture electrons, the
2:36:08
Speaker 1: first molecule expected to form was heviium hydride ion. It
2:36:13
Speaker 1: consists of helium bonded with ionized hydrogen and is written
2:36:17
Speaker 1: by scientists as he H plus. Chemists predicted its existence
2:36:23
Speaker 1: in space for decades, yet finding it proved surprisingly difficult.
2:36:28
Speaker 1: Laboratory experiments could make it, but astronomical searches repeatedly failed.
2:36:34
Speaker 1: Consummation finally came from observations of the planetary nebula n
2:36:39
Speaker 1: Gc seven zero two seven. Conditions there recreate some of
2:36:44
Speaker 1: the chemistry needed to produce the ion strongly enough for
2:36:47
Speaker 1: its distinctive infrared signal to become detectable. The discovery did
2:36:52
Speaker 1: more than identify an unusual molecule. It confirmed an important
2:36:57
Speaker 1: step in models describing the universe's fives chemistry. Helium hydride
2:37:02
Speaker 1: could later react and help open pathways toward molecular hydrogen,
2:37:07
Speaker 1: which became crucial for cooling primordial gas before early stars formed.
2:37:12
Speaker 1: The first molecular bond in cosmic history was therefore lightly
2:37:16
Speaker 1: created from two of the simplest elements available, long before
2:37:20
Speaker 1: planets provided anything resembling the chemical complexity surrounding us today.
2:37:26
Speaker 1: Technetium appears naturally only in tiny quantities and short lived
2:37:31
Speaker 1: cosmic environments. Every isotope of technetium is radioactive, none survives indefinitely,
2:37:39
Speaker 1: which explains why substantial primordial deposits disappeared from Earth long ago.
2:37:45
Speaker 1: Yet technetium does exist naturally because ongoing nuclear processes can
2:37:50
Speaker 1: create fresh atoms. Tiny amounts arise from spontaneous fission in
2:37:55
Speaker 1: uranium ores. Far more dramatically, a stronomer discovered technetium inside
2:38:02
Speaker 1: certain aging stars. That observation became a breakthrough in understanding
2:38:07
Speaker 1: how stars manufacture elements. If technetium appeared in a stellar
2:38:12
Speaker 1: atmosphere despite having no stable isotope, it must have been
2:38:16
Speaker 1: produced relatively recently on astronomical time scales. The star itself
2:38:21
Speaker 1: was therefore making heavy nuclei and transporting them toward its surface.
2:38:26
Speaker 1: This provided direct evidence for stellar nucleosynthesis while the process
2:38:31
Speaker 1: was still unfolding. Technetium can formed through neutron capture reactions
2:38:36
Speaker 1: inside evolved giant stars before convective mixing brings newly created
2:38:41
Speaker 1: material outward. Its name comes from a word meaning artificial,
2:38:46
Speaker 1: because it was the first element produced artificially before being
2:38:50
Speaker 1: securely identified in nature. That history gives it an unusual identity.
2:38:55
Speaker 1: Humanity first knew it as something manufactured in a laboratory
2:39:00
Speaker 1: then discovered that stars had been quietly producing the same
2:39:03
Speaker 1: unstable element for billions of years. Promethium is produced by stars,
2:39:08
Speaker 1: but rarely survives for long. Between neodymium and semarium sits
2:39:13
Speaker 1: an element with no stable isotope at all. Promethium is
2:39:17
Speaker 1: radioactive in every form, and even its longest lived isotopes
2:39:21
Speaker 1: decay on timescales tiny compared with the age of Earth.
2:39:25
Speaker 1: Any primordial promethium incorporated into our planet disappeared billions of
2:39:30
Speaker 1: years ago. The atoms present naturally today must therefore have
2:39:35
Speaker 1: been created more recently. Trace amounts can arise through the
2:39:40
Speaker 1: radioactive decay of heavier elements and through nuclear reactions. Stars
2:39:45
Speaker 1: can also manufacture promethium during neutron capture processes, although detecting
2:39:50
Speaker 1: it astronomically as challenging because its spectral signatures are faint
2:39:54
Speaker 1: and surrounding stellar atmospheres containing many competing line Most prometheum
2:40:02
Speaker 1: encountered in practical research is produced artificially in reactors. Its
2:40:08
Speaker 1: rarity once created a conspicuous gap in the periodic table.
2:40:12
Speaker 1: Chemists knew an element had to occupy the position, but
2:40:16
Speaker 1: struggled twice lated convincingly until fission products provided enough material.
2:40:21
Speaker 1: During the twentieth century. Prometheum illustrates how temporary an element
2:40:26
Speaker 1: can be on cosmic time scales. The laws of physics
2:40:30
Speaker 1: permit its nuclei to form, yet none possess the stability
2:40:34
Speaker 1: required to accumulate naturally. Over geological ages, every promethium atom
2:40:40
Speaker 1: is effectively living on borrowed nuclear time. Astetine may be
2:40:45
Speaker 1: the rarest naturally occurring element in Earth's crust. At any
2:40:49
Speaker 1: given moment, the entire natural supply of asteteine in Earth's
2:40:53
Speaker 1: crust may amount to less than a gram. Some estimates
2:40:57
Speaker 1: place it far below that. The reason is not that
2:41:01
Speaker 1: astetine cannot form. It appears briefly in radioactive decay chains
2:41:06
Speaker 1: involving much heavier elements. The problem is survival. Every known
2:41:13
Speaker 1: astetine isotope is unstable, and the longest lived examples persist
2:41:18
Speaker 1: for only hours. An atom created naturally therefore disappears relatively
2:41:24
Speaker 1: quickly through further radioactive decay. New ones are continuously generated,
2:41:30
Speaker 1: while older one spanish, leaving an extraordinarily small standing population.
2:41:37
Speaker 1: Asteteine lies beneath iodine on the periodic table and belongs
2:41:41
Speaker 1: to the halogen family. But its extreme scarcity makes its
2:41:45
Speaker 1: bulk chemical behavior difficult to study directly. Researchers usually create
2:41:51
Speaker 1: tiny quantities artificially and must work before the sample decays away.
2:41:56
Speaker 1: Nobody has ever assembled a visible lump of elemental asteris enough.
2:42:01
Speaker 1: Concentrated material would also heat itself through radioactivity, creating additional
2:42:06
Speaker 1: experimental problems. It occupies a strange position among the elements.
2:42:12
Speaker 1: Asteteine is naturally produced on Earth right now, yet almost
2:42:16
Speaker 1: none exists at any single instant because nuclear instability erases
2:42:20
Speaker 1: it nearly as quickly as nature makes it. Super Heavy
2:42:24
Speaker 1: elements exist for moments before their unstable nuclei break apart,
2:42:29
Speaker 1: but the far end of the periodic table, scientists create
2:42:33
Speaker 1: atoms that nature does not leave lying around for us
2:42:36
Speaker 1: to collect. Super heavy elements contain enormous numbers of protons
2:42:41
Speaker 1: packed into one nucleus. The electrical repulsion between those positively
2:42:47
Speaker 1: charged particles makes stability increasingly difficult. Researchers produce these atoms
2:42:54
Speaker 1: by accelerating one kind of nucleus into another and hoping
2:42:58
Speaker 1: that a rare collision causes them to fees. Most attempts fail.
2:43:03
Speaker 1: Successful experiments may create only a few atoms. After weeks
2:43:07
Speaker 1: or months of bombardment. The new nucleus then announces itself
2:43:12
Speaker 1: through a chain of radioactive decays. Some super heavy isotopes
2:43:16
Speaker 1: survive for milliseconds, while others persist longer. Nuclear physicists are
2:43:22
Speaker 1: searching for a predicted region known as the island of stability,
2:43:26
Speaker 1: where particular combinations of protons and neutrons might produce unexpectedly
2:43:31
Speaker 1: longer lifetimes. Reaching it would test our understanding of how
2:43:35
Speaker 1: nuclei are structured. Elements this heavy also push chemistry into
2:43:40
Speaker 1: unusual territory, because electrons move so rapidly near the highly
2:43:44
Speaker 1: charged nucleus that relativistic effects become important. At the edge
2:43:49
Speaker 1: of the periodic table, discovering an element can mean creating
2:43:53
Speaker 1: just a handful of atoms and watching how they disappear.
2:43:58
Speaker 1: Presolar grains contain mineral older than the Solar System itself.
2:44:03
Speaker 1: Some meteorites contain microscopic pieces of solid matter that existed
2:44:07
Speaker 1: before the Sun was born. These presolar grains survived the
2:44:11
Speaker 1: collapse of the cloud that formed our Solar system and
2:44:14
Speaker 1: became trapped inside primitive asteroids. When pieces of those asteroids
2:44:19
Speaker 1: later reached Earth as meteorites, laboratories gained access to material
2:44:24
Speaker 1: originating around ancient stars. The grains can be made from
2:44:29
Speaker 1: substances such as silicon, carbide and graphite. Their isotope ratios
2:44:34
Speaker 1: are dramatically different from typical Solar System material, which reveals
2:44:38
Speaker 1: that they formed in other stellar environments. Some condensed in
2:44:43
Speaker 1: winds from aging giant stars. Others appear to have formed
2:44:47
Speaker 1: in supernova ejecta. Researchers isolate them through painstaking chemical procedures
2:44:54
Speaker 1: and examine individual grains using extremely sensitive instruments. Sutain specimens
2:45:00
Speaker 1: have ages billions of years greater than the Solar System itself.
2:45:04
Speaker 1: Holding a meteorite can therefore mean holding dust that already
2:45:08
Speaker 1: existed before Earth, the planets, or the Sun. These grains
2:45:12
Speaker 1: survived stellar outflows, interstellar travel, the birth of a new
2:45:17
Speaker 1: star system, and eventual incorporation into rock. Their tiny crystals
2:45:23
Speaker 1: are actual pieces of astrophysical history, rather than merely light
2:45:27
Speaker 1: arriving from distant objects. Star dust crystals preserve chemical fingerprints
2:45:33
Speaker 1: from individual vanished stars. A microscopic grain can reveal what
2:45:38
Speaker 1: happened inside a star that no longer exists. Different nuclear
2:45:43
Speaker 1: reactions create distinctive proportions of isotopes. When dust condenses around
2:45:48
Speaker 1: an aging star or inside expanding supernova debris, those ratios
2:45:53
Speaker 1: become locked into the solid material. Billions of years later,
2:45:58
Speaker 1: Scientists can measure them atom by atom inside presolar grains.
2:46:04
Speaker 1: The pattern may identify whether the parent star was a
2:46:07
Speaker 1: red giant, a nova, or a stellar explosion. Some grains
2:46:12
Speaker 1: contain isotopic combinations that expose specific neutron capture reactions occurring
2:46:18
Speaker 1: deep inside ancient stars. Others preserve evidence that material from
2:46:23
Speaker 1: different layers of a supernova mixed together before the dust crystallized.
2:46:29
Speaker 1: This makes star dust fundamentally different from most astronomical evidence.
2:46:34
Speaker 1: Telescopes analyze light from large populations or distant surfaces. A
2:46:39
Speaker 1: presolar crystal can provide a physical sample from one particular
2:46:43
Speaker 1: stellar environment. The original star may have disappeared before the
2:46:47
Speaker 1: Solar system formed, but part of its chemical history survived
2:46:51
Speaker 1: in solid form. Scientists can place that grain into an
2:46:55
Speaker 1: instrument on Earth and reconstruct events that occurred inside and
2:46:59
Speaker 1: otherwise unreachable star. Cosmic archaeology sometimes operates on objects smaller
2:47:05
Speaker 1: than the grain of dust. The cosmic microwave background contains
2:47:09
Speaker 1: exceptionally rare patches of unusual temperature across most of the sky.
2:47:14
Speaker 1: The after glow of the early universe is astonishingly uniform.
2:47:19
Speaker 1: Tiny temperature differences reveal the density fluctuations that eventually grew
2:47:23
Speaker 1: into galaxies. Against that regular pattern, A few unusually large
2:47:29
Speaker 1: features have attracted intense attention. The best known is the
2:47:33
Speaker 1: CMB cold spot. It covers a broad area of sky
2:47:38
Speaker 1: where the microwave background appears cooler than average in a
2:47:41
Speaker 1: statistically unusual way. Astronomers have investigated whether a vast under
2:47:47
Speaker 1: dense region along the line of sight could account for
2:47:50
Speaker 1: part of the effect by subtly changing the energy of
2:47:53
Speaker 1: passing photons. Such structures do not seem to explain the
2:47:57
Speaker 1: entire anomaly straightforwardly. Another possibility is much less dramatic. In
2:48:03
Speaker 1: a universe containing campless random fluctuations, rare patterns occasionally appear
2:48:09
Speaker 1: simply by chance. More speculative explanations have also been proposed,
2:48:15
Speaker 1: but none is required by current evidence. The cold spot
2:48:19
Speaker 1: fascinates cosmologists precisely because unusual does not automatically mean new physics.
2:48:27
Speaker 1: Researchers must distinguish a genuine clue from an improbable but
2:48:31
Speaker 1: natural statistical accident. One strange patch in ancient radiation can
2:48:36
Speaker 1: therefore become a rigorous test of how confidently we understand
2:48:40
Speaker 1: the randomness built into our cosmological models. Intelligent observers may
2:48:45
Speaker 1: be among the rarest outcomes of cosmic evolution. The universe
2:48:50
Speaker 1: has spent billions of years producing stars and planets, yet
2:48:54
Speaker 1: we currently possess only one confirmed example of a species
2:48:58
Speaker 1: capable of investigating cosmic history. Whether that reflects genuine rarity
2:49:04
Speaker 1: or simply our limited search remains completely unknown. Life itself
2:49:09
Speaker 1: may begin readily when suitable chemistry exists, while technological intelligence
2:49:14
Speaker 1: could require a much more improbable sequence. Evolution on Earth
2:49:19
Speaker 1: offers no evidence that intelligence was an inevitable destination. Complex
2:49:25
Speaker 1: life assisted for immense periods without radio, telescopes or spacecraft.
2:49:30
Speaker 1: Many successful organisms never developed technology because natural selection rewards
2:49:35
Speaker 1: survival rather than scientific capability. At the same time, one
2:49:41
Speaker 1: example cannot reveal the underlying probability. The Milky Way contains
2:49:47
Speaker 1: vast numbers of planets, and even an extremely unlikely process
2:49:51
Speaker 1: could happen repeatedly across such a large population. Searches for
2:49:56
Speaker 1: signals and other signs of technology are beginning to test
2:49:59
Speaker 1: that disability. No confirmed extraterrestrial civilization has yet been found.
2:50:06
Speaker 1: This leaves humanity facing one of science's most extraordinary uncertainties.
2:50:11
Speaker 1: Intelligence capable of understanding the universe might be common enough
2:50:15
Speaker 1: to appear many times within a galaxy, or so rare
2:50:18
Speaker 1: that a world asking these questions is itself a cosmic exception.
2:50:23
Speaker 1: And that brings us to the end of our journey
2:50:26
Speaker 1: through some of the rarest things in the universe. We've
2:50:29
Speaker 1: encountered objects that exist only under extraordinary conditions. We've seen
2:50:34
Speaker 1: stars caught in brief stages of their lives, planets surviving
2:50:38
Speaker 1: in places that seem almost impossible, and particles that can
2:50:42
Speaker 1: cross vast distances while barely touching anything at all. Some
2:50:47
Speaker 1: of these rarities of the remains of violent events. Others
2:50:51
Speaker 1: are ancient survivors from the earliest chapters of cosmic history,
2:50:56
Speaker 1: and some may still exist only as possibilities, waiting for
2:50:59
Speaker 1: better time telescopes or more sensitive instruments to reveal whether
2:51:03
Speaker 1: nature truly made them. What makes these discoveries so remarkable
2:51:08
Speaker 1: is not simply that they are uncommon. It is that
2:51:12
Speaker 1: each one shows us another way the universe can behave.
2:51:15
Speaker 1: And now, with all of that behind us, there is
2:51:18
Speaker 1: nothing more you need to follow. Let those distant stars
2:51:23
Speaker 1: continue without you for a while. Let the galaxies turned
2:51:27
Speaker 1: slowly in the darkness. The universe will keep moving long
2:51:31
Speaker 1: after this moment has passed. Allow your breathing to settle
2:51:35
Speaker 1: into its own rhythm. Let your shoulders soften against whatever
2:51:39
Speaker 1: is supporting you. There is nowhere else you need to
2:51:43
Speaker 1: be right now. If you enjoyed this journey, you're always
2:51:47
Speaker 1: welcome to like the video, subscribe to the channel, or
2:51:50
Speaker 1: leave a thought below. And if you happen to still
2:51:53
Speaker 1: be awake, there should be another sleepy science journey waiting
2:51:57
Speaker 1: for you on the screen. You can follow it whenever
2:52:00
Speaker 1: you're ready, and let the next subject carry your thoughts
2:52:03
Speaker 1: a little further. But for now, simply rest, Let the
2:52:08
Speaker 1: questions fade, Let the day grow distant, and allow yourself
2:52:13
Speaker 1: to drift naturally towards sleep. Sleep well, and good night,
2:53:02
Speaker 1: says included Indi