Latest / Boring Science / The Universe_s Most Dramatic Moment_ Star Supernova

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The Universe_s Most Dramatic Moment_ Star Supernova · Boring Science

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  Speaker 1: Right now, somewhere in the universe, a star is dying,
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  not quietly fading away, but preparing for the most violent
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  explosion nature can produce a super nova, and when it happens,
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  that single star will briefly outshine an entire galaxy of
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  hundreds of billions of suns. Picture this. You're standing outside
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  on a clear night, looking up at the familiar constellations.
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  Tomorrow night, you look up again, and there's a new
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  star blazing, so bright it casts shadows visible even in daylight.
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  That's what happened in one thousand and six a d
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  when a super nova appeared in the constellation Lupus. It
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  was sixteen times brighter than Venus. People could read by
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  its light at midnight. But here's what makes this truly extraordinary.
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  That star was seventh thousand light years away, seven thousand
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  light years, and it was still bright enough to illuminate
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  medieval manuscripts. What kind of explosion does that. We're talking
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  about an event so energetic that in a few seconds
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  it releases more power than our sun will produce in
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  its entire ten billion year lifetime, more energy than a
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  trillion trillion nuclear bombs. Numbers so large they stop making sense. Yet,
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  for all their violence, supernovae aren't just cosmic fireworks. They're foundational.
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  The calcium in your bones, the iron in your blood,
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  the oxygen you're breathing right now, all of it was
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  forged in the heart of dying stars and scattered across
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  the cosmos by supernova explosions. You are literally made of
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  star dust, but not the gentle, romantic kind, the violent,
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  explosive kind. So what actually happens when a star goes
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  sup and over? How does something that's been peacefully burning
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  for millions of years suddenly tear itself apart with such fury?
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  And why do only certain stars explode while others fade
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  quietly into the cosmic night. The story begins not with death,
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  but with life, with how stars work in the first place.
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  Stars are engines of nuclear fusion. At their cause, temperatures
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  reach fifteen million degrees celsius, hot enough to slam hydrogen
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  atoms together so hard they fuse into helium, releasing tremendous
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  energy in the process. This energy pushes outward while gravity
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  pulls inward. For most of a star's life, these forces
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  balance perfectly. It's a standoff pressure versus gravity, and as
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  long as there's fuel to burn, the star stays stable.
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  But here's the thing about fusion. It's picky. Hydrogen fuses
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  into helium easily enough, but once you've built up helium,
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  fusing it into heavier elements requires even higher temperatures and pressures.
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  Carbon needs more energy, still, oxygen more. Again, each fusion
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  stage burns faster than the last. A star might spend
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  ten million years burning hydrogen, a million years, burning helium,
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  a thousand years, burning carbon, oxygen a year, silicon a week.
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  The star is racing toward a finish line. It can't
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  see now. You might think this process continues indefinitely, keep
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  fusing heavier and heavier elements forever, But physics has other plans.
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  Because there's one element where everything stops. Iron. Iron is special.
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  It's the most stable element in the universe. Fusing iron
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  doesn't release energy, it absorbs energy. Iron is the end
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  of the line, the point where fusion becomes a losing game.
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  So imagine you're a massive star. You've spent millions of
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  years building up layers like a cosmic onion, Hydrogen burning
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  in the outermost shell, helium burning beneath that, carbon, neon,
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  oxygen silicon, each layer burning at increasingly insane temperatures, and
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  at the very center iron dead, iron inert, taking up
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  space but contributing nothing. The core keeps growing more silicon
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  fuses into iron, The iron core gets heavier and heavier,
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  and gravity starts to win. For stars like our Sun,
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  this isn't a problem. The Sun will never build an
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  iron core. It'll puff up into a red giant, shed
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  its outer layers, and settle down as a white dwarf,
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  a slow, dignified retirement. But for stars at least eight
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  times more massive than the Sun, they're heading for something
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  very different. The iron core grows until it reaches a
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  critical threshold, about one point four times the mass of
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  our Sun compressed into a sphere roughly the size of Earth.
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  At this point, the pressure becomes so extreme that something
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  remarkable happens. Electrons get crushed into protons. They combine to
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  form neutrons and release ghostly particles called neutrinos. The core,
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  which was being supported by electron pressure, suddenly loses that support,
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  and it collapses, not slowly, not gradually. In less than
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  a second, the core implodes, It speeds up to twenty
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  three percent of the speed of light twenty three percent
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  of light speed. The temperature skyrockets to one hundred billion degrees.
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  That's hotter than any temperature anywhere else in the universe
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  except during the Big Bang itself. The entire core, containing
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  more mass than our Sun, collapses to a sphere just
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  thirty kilometers across thirty kilometers from something the size of Earth.
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  The collapse happens so fast that the outer layers of
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  the star don't even know it's happening yet. They're still
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  falling inward, expecting the core to be there to catch them.
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  But the core isn't there anymore. It's compressed into something else,
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  entirely a ball of neutrons, so dense that a teaspoon
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  would weigh a billion tons, a neutron star, or, if
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  the star was massive enough, something even stranger, a black hole.
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  Now here's where it gets violent. The in falling outer
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  layers slam into this impossibly dense core and bounce like
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  a rubber ball hitting concrete, except this ball is made
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  of stellar material moving at a significant fraction of light speed,
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  and the concrete is a neutron star. The bounce creates
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  a shockwave, a wall of pressure and energy that races
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  back outward through the star at ten thousand kilometers per second.
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  Everything in its path gets obliterated and accelerated to escape velocity.
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  The star doesn't just explode, it detonates. Within hours. The
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  shockwave punches through the star's surface in what astronomers call
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  the shock breakout. This is the moment when the supernova
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  becomes visible. A flash of X rays and ultraviolet light
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  announces to the universe that another star has died. But
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  most of the energy doesn't go into light. It goes
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  into neutrinos. Remember those ghostly particles released when electrons merged
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  with protons. In ten seconds, the collapsing core releases ten
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  to the power of fifty eight neutrinos. That number is
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  so large it's almost meaningless, more neutrinos than there are
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  stars in a million galaxies. These neutrinos carry away ninety
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  nine percent of the explosion's energy. They pass through matter
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  like it isn't even there. Trillions of them are passing
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  through your body right now from distant supernova, and you
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  don't feel a thing. But in nineteen eighty seven we
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  caught them. Supernova nineteen eighty seven A exploded in the
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  large which Magellanic Cloud, a small galaxy near our own.
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  It was the closest supernova visible to the naked eye
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  in four hundred years, and about three hours before the
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  light reached Earth, neutrino detectors in Japan and Ohio registered
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  twenty five neutrinos, arriving within thirteen seconds, twenty five out
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  of ten to the fifty eight. That's like standing in
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  a rainstorm and catching twenty five specific raindrops. But those
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  twenty five neutrinos told us something profound. The theoretical models
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  were right. Core collapse really does produce a massive neutrino burst.
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  We'd caught the star in the act of dying, and
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  because neutrinos travel at nearly light speed and pass through
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  matter easily, they escaped the star hours before the light did.
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  The light had to fight its way through thousands of
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  kiloma of stellar material. The neutrino's just left. For the
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  first time, we detected a supernova in neutrinos before we
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  saw it in light. The shock wave, meanwhile, is doing
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  something extraordinary as it tears through the star's outer layers.
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  It's compressing and heating material to such extreme temperatures that
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  new nuclear reactions ignite, not fusion to release energy, fusion
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  to create elements. Remember how iron was the end of
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  the line for normal fusion. Well, in a supernova, all
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  bets are off. The conditions are so extreme that elements
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  heavier than iron can form cobalt, nickel, copper, zinc, keep going, silver, tin, gold, platinum, lead, uranium.
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  Every atom of gold in every ring, every coin, every
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  circuit board was created in a supernova explosion. The extreme
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  pressures and temperatures in that expanding shockwave are the only
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  natural forge capable of building these heavy elements. A single
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  supernova can produce more gold than exists in Earth's entire crust.
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  The shockwave expands outward at five to twenty thousand kilometers
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  per second, roughly six percent of light speed. It's carrying
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  with it all the elements The stars spent millions of
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  years creating oxygen, carbon, silicon, iron, and all those heavy
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  elements borne in the explosion itself. This material slams into
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  the surrounding interstellar gas, heating it, compressing it, mixing with it.
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  Over thousands of years, the expanding debris will slow down
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  and cool off, forming what we call a supernova remnant,
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  A beautiful glowing shell of gars expanding through space. The
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  crab Nebula is one such remnant. It's what's left of
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  the supernova observed by Chinese astronomers in ten fifty four AD.
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  That explosion was visible in daylight for twenty three days
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  and remain visible at night for six hundred fifty three days,
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  nearly two years. Today, the crab Nebula spans eleven light
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  years and is still expanding. At its center, sits a
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  neutron star spinning thirty times per second, the crushed core
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  of the star that exploded. But not all supernovae are
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  created equal. What I've just described is a core collapse supernova,
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  also called a type two supernova. These require massive stars
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  at least eight times the mass of our Sun, sometimes
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  up to two hundred solar masses. There's another kind, Type
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  one A and its stranger Type one A. Supernovae don't
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  come from massive stars at all. They come from white dwarfs,
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  the dense remnants of stars like our Sun that have
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  already died once. Here's how it works. A white dwarf
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  sits in a binary system with another star, maybe a
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  red giant, maybe another white dwarf. A material from the
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  companion star falls onto the white dwarf's surface. Slowly, over
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  thousands or millions of years, the white dwarf gets heavier
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  and heavier until it approaches a critical mass one point
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  four to four times the mass of the Sun. This
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  is called the Chandrasercar limit, and it's a hard boundary.
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  Below this mass, electron degeneracy pressure can support the white
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  dwarf against gravity. Above it, the pressure fails. The carbon
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  and oxygen in the white dwarf's core reach ag nission temperature,
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  and the entire star detonates in a runaway fusion reaction.
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  Unlike core collapse supernovae, which leave behind a neutron star
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  or black hole, type one A supernovae destroy their stars completely.
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  Nothing remains but an expanding cloud of debris. These explosions
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  are remarkably consistent. They all reach roughly the same peak
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  brightness because they all happen at the same mass threshold.
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  This makes them incredibly useful as cosmic distance markers. If
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  you know how bright something actually is, and you measure
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  how bright it appears, you can calculate how far away
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  it is. Type one A supernovae are one of the
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  main tools we use to measure the expansion rate of
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  the universe. In fact, it was observations of distant type
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  one A supernovae that led to the discovery of dark
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  energy in nineteen ninety eight. But whether we're talking about
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  core collapse or thermonuclear explosion, the result is similar. A
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  star that was stable for millions of years suddenly releases
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  more energy than seems physically possible. The numbers are staggering.
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  A typical supernova releases about ten to the forty fourth
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  duels of energy. That's a one, followed by forty four
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  zeros in watts. The power output peaks at ten to
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  the forty five or forty six watts. For comparison, our
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  Sun outputs about four times ten to the twenty six watts.
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  A supernova for a brief time can be five trillion
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  times more luminous than the Sun, five trillion times brighter
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  than the object that lights our entire world. And here's
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  something that might blow your mind. On April tenth, twenty
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  twenty four, astronomers detected a supernova designated s N two
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  zero two four ggi. Just twenty six hours later, they
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  pointed the very large telescope at it twenty six hours.
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  That's barely more than a day. What they saw was unprecedented.
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  They caught the shock breakout, the actual moment when the
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  shock wave punches through the star's surface. This phase lasts
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  only a few hours, and catching it requires being incredibly
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  lucky or incredibly fast. The observations revealed something unexpected. The
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  initial blast wasn't spherical. It was shaped like an olive
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  elongated asymmetric. This tells us something profound about how stars explode.
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  The physics isn't as simple as a uniform shock wave
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  expanding in all directions. There are instabilities, asymmetries. The star's rotation,
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  magnetic fields, and internal structure all affect how it tears
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  itself apart. Every supernova is unique, a fingerprint of the
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  star that died. But here's what connects all of this.
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  From the crushing collapse of an iron core to the
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  runaway fusion of a white dwarf, from the olive shaped
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  blast of SN twoenty twenty four gg i to the
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  perfectly spherical expansion of other explosions, It's all driven by
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  the same fundamental forces. Gravity trying to crush everything into
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  a point, pressure pushing back, and nuclear physics determining what
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  happens when you can press matter beyond all reasonable limits.
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  The question is what happens next after the shockwave parts,
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  after the light fades, after the neutrinos have scattered across
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  the cosmos, what's left behind and how does that remnant
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  continue to shape the universe around it. The expanding debris
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  field becomes a cosmic laboratory. Temperatures in the billions of degrees,
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  pressures that make the center of our sun look like
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  a gentle breeze, And in these extreme conditions something remarkable happens.
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  Elements that could never form in a normal star suddenly
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  come into existence. Iron was the ceiling for normal fusion,
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  the end of the line, but in a supernova's shock wave,
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  that ceiling shatters. The shock compresses material so violently that
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  nuclei slam together with enough force to overcome the energy barrier.
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  They fuse into heavier elements cobalt, nickel, copper, zinc, all
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  the way up to uranium and beyond. This is shockwave nucleosynthesis,
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  and it's the only place in the universe where many
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  elements can form. The gold in jewelry, the silver in electronics,
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  the uranium in nuclear reactors. None of these existed in
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  the early universe. They weren't created in the Big Bang.
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  They couldn't form in stellar cores. They required the violence
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  of a supernova to be forged. Think about that for
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  a moment. Every atom of gold on Earth was created
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  in a stellar explosion. Every platinum ring, every gold bar
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  in a vault somewhere, all of it came from a
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  star that died before our sun was born. These atoms
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  were scattered into space, mixed with hydrogen and helium, and
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  eventually condensed into the cloud that became our solar system.
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  You're made of star dust. That phrase gets thrown around
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  a lot, but it's literally true. The calcium in your
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  bones was created in a supernova. The iron in your
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  blood was forged in the final moments of a dying star.
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  The oxygen you're breathing right now was synthesized in stellar
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  cores and scattered by supernova. Every breath you take contains
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  atoms that were once inside a star, but the explosion
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  doesn't create elements uniformly. Different regions of the expanding debris
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  have different compositions. The innermost layers, closest to where the
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  core collapsed are rich in iron group elements iron, nickel, cobalt.
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  These were the last elements the star created before it died.
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  Moving outward, you find lighter elements silicon, sulfur, oxygen. These
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  came from earlier stages of the star's life. The outer
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  layers contain helium and hydrogen barely processed by nuclear reactions.
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  The debris field is stratified, layered like an onion, with
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  each shell telling a story about a different phase of
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  the star's evolution. As this material expands, it collides with
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  the surrounding interstellar medium, the gas and dust floating between stars.
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  This collision creates a shock front, not the initial shockwave
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  from the explosion, but a boundary where the fast moving
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  debris slams into slower moving gas. This collision heats the
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  gas to millions of degrees, it glows in X rays,
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  and it creates what we call a supernova remnant. The
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  crab Nebula is one of the most famous examples, created
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  by the supernova of ten fifty four AD. Chinese astronomers
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  saw it appear a new star, bright enough to see
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  in daylight for twenty three days, visible at night for
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  six hundred fifty three days, Nearly two years of watching
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  a star that shouldn't exist slowly fade from view. Today,
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  almost a thousand years later, the debris is still expanding,
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  still glowing, still visible through telescopes as a complex filamentary structure,
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  gases moving at thousands of kilometers per second, magnetic fields
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  twisted into intricate patterns, and at the center, something we
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  haven't discussed yet, something that survived the explosion, a neutron star.
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  The collapsed core of the original star only about twenty
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  kilometers across, less than the width of a city, containing
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  more mass than our sun. It spins thirty times per second.
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  Each rotation sweeps a beam of radiation across space, like
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  a cosmic lighthouse. We see these beams as pulses, regular precise,
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  so precise we initially thought they might be signals from
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  alien civilizations. The crab pulsar was one of the first
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  discovered proof that neutron stars weren't just theoretical objects. They
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  were real, dense beyond comprehension. A teaspoon of neutron star
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  material would weigh a billion tons on Earth, gravity so
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  strong that if you dropped something from a height of
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  one meter, it would hit the surface at millions of
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  kilometers per hour, but not all supernovae leave neutron stars behind.
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  If the original star was massive enough, the core collapse
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  doesn't stop at neutron degeneracy. It keeps going, crushing neutrons themselves,
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  overcoming every force physics can muster, and creating a black hole.
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  The transition point is somewhere around twenty to twenty five
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  solar masses. Stars below that limit create neutron stars, stars
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  above it create black holes, but the exact boundary is fuzzy.
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  It depends on the star's composition, its rotation rate, how
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  much mass it shed during its lifetime. Every star is different.
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  Cassiopeia A is another famous remnant created by a supernova
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  that should have been visible from Earth around sixteen eighty,
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  but nobody recorded seeing it. Perhaps it was obscured by dust,
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  perhaps it happened during cloudy weather, or perhaps the explosion
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  was unusually faint. We'll never know for certain. What we
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  we do know is that the remnant is extraordinary, the
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  fastest moving debris we've ever measured in a supernova, filaments
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  of gas racing outward at thirteen point four million miles
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  per hour, about two percent of light speed. Carrying kinetic
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  energy that staggers the imagination. The shockwave from Cassiopaya A
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  is still expanding today, still sweeping up interstellar gas, still
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  heating it to millions of degrees, and in the process
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  it's creating cosmic rays, high energy particles accelerated to nearly
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  light speed by the magnetic fields in the shock front.
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  These cosmic rays are everywhere right now. Thousands of them
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  are passing through your body every second, most of them
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  created in supernova remnants scattered across the galaxy. Their one
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  reason we know supernovae are important beyond just making heavy
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  elements their cosmic particle accelerators, Nature's own version of the
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  large hadron collider, but vastly more powerful. The energy in
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  a supernova remnant doesn't disappear quickly. It takes tens of
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  thousands of years for the debris to slow down, to
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  merge with the interstellar medium, to cool, and fade from view.
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  During that time, the remnant goes through stages. First free expansion,
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  the debris moves outward at constant velocity, barely interacting with
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  surrounding gas because there's so little of it. This phase
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  lasts anywhere from decades to a few centuries, depending on
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  how dense the local environment is. Then the said of
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  tailor phase begins. The remnant has swept up enough interstellar
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  gas that it starts to matter slows, the shock front strengthens,
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  the remnant becomes a bubble of hot, glowing gas pushing
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  into the cooler material around it. This phase can last
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  thousands of years. Eventually, the remnant cools enough that it
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  stops glowing in X rays. It becomes just another cloud
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  of gas in the interstellar medium, slightly enriched in heavy
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  elements compared to its surroundings, slightly denser and potentially a
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  trigger for new star formation. Because when a supernova remnant
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  plows into a molecular cloud, it compresses the gas, squeezes it,
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  and compressed gas is unstable. Regions that are slightly denser
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  than average begin to collapse under their own gravity. They
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  fragment into smaller clumps, and those clumps become the seeds
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  of new stars. This is how star formation propagates through
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  a galaxy. One generation of stars lives and dies, their
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  supernova trigger the formation of the next generation. It's a
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  cycle that's been running for billions of years. The reason
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  our galaxy is full of stars of different ages. The
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  reason new stars are still forming today our own Sun
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  might have been triggered by a supernova. There's evidence in meteorites,
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  specifically in their composition. They contain isotopes of elements that
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  decay quickly, so quickly they shouldn't still be around unless
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  they were created shortly before the Solar System formed. The
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  most likely source a nearby supernova that enrich the cloud
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  of gas that became our Solar System and possibly triggered
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  its collapse. That's true. We owe our existence to a
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  star that died four point six billion years ago, a
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  star will never know the name of, never see, but
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  whose final explosions set in motion the chain of events
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  that led to planets, to Earth, to life to you
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  reading these words right now. But supernova remnants do more
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  than trigger star formation. They heat the interstellar medium, keep
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  it from collapsing too quickly, too completely. Without supernova, galaxies
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  will be very different places. Gas would cool condense form
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  stars far more rapidly than it does. The star formation
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  rate will be higher, but the stars would be smaller
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  on average, less massive. It's a balance. Supernova inject energy
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  into the galaxy, heat things up, stir the pot. This
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  prevents runaway star regulates the process ensures that galaxies like
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  ours form stars steadily over billions of years, rather than
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  burning through all their gas in a single burst. The
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  debris from a supernova also enriches the interstellar medium. Before
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  the first supernova, the universe contained only hydrogen, helium, and
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  trace amounts of lithium. Everything else had to be created
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  in stars and distributed by explosions. Generation after generation of
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  stars lived and died, each one adding more heavy elements
• 30:41
  to the cosmic mix. The first stars were massive, hundreds
• 30:46
  of times the Sun's mass. They lived fast and died young.
• 30:51
  Their supernova scattered the first heavy elements into space. The
• 30:56
  next generation of stars formed from gas slightly enriched in
• 31:01
  carbon and oxygen. Those stars lived and died, added more elements,
• 31:07
  and so the cycle continued. Our Sun is a third
• 31:11
  or fourth generation star. Maybe later it formed from gas
• 31:15
  already enriched in heavy elements. That's why Earth exists, why
• 31:20
  rocky planets could form, why we have the elements necessary
• 31:24
  for complex chemistry for life. Every supernova adds to this enrichment,
• 31:31
  mixes new elements into the galactic gene pool and slowly,
• 31:36
  over billions of years, the composition of the galaxy changes.
• 31:42
  The first galaxies were pure hydrogen and helium. Modern galaxies
• 31:47
  have a few percent heavy elements. In another few billion years,
• 31:52
  that percentage will be higher. Still, there's another way to
• 31:56
  think about this. Every element heavier than helium in your
• 32:00
  body was created in a star. Most of those elements
• 32:05
  were scattered by supernova. You are quite literally made from
• 32:10
  the ashes of dead stars, recycled stellar material, atoms that
• 32:17
  have been through multiple generations of stars, multiple cycles of
• 32:21
  birth and death. The oxygen in water, the carbon in proteins,
• 32:26
  the nitrogen in DNA, the calcium in bones, the phosphorus
• 32:30
  in ATP, the ion in hemoglobin. All of it was
• 32:34
  forged in stellar cores or supernova shock waves. All of
• 32:38
  it was scattered into space by dying stars. All of
• 32:42
  it eventually found its way into the cloud that formed
• 32:45
  our Solar system. Supernova are more than just explosions. They're
• 32:51
  the mechanism by which stars give back to the universe,
• 32:55
  how they enrich the cosmos, how they make future generations
• 32:59
  of stars and planets possible. Without supernovae, the universe would
• 33:05
  be a much simpler place, no rocky planets, no complex chemistry,
• 33:11
  no life, But there's something else. Supernova create something we
• 33:17
  haven't fully explored yet. When that core collapses, when it
• 33:22
  reaches densities beyond anything found in normal matter, what exactly
• 33:28
  is left behind? What is a neutron star really? And
• 33:33
  what happens in the most extreme cases when even neutron
• 33:37
  stars can't form. That's the question we need to answer.
• 33:42
  What happens when gravity wins so completely that even atoms
• 33:46
  can't survive the remnant left behind depends on the mass
• 33:51
  of the original core. If the core is between about
• 33:55
  one point four and three solar masses, you get a
• 33:58
  neutron star. Above that threshold, something even stranger emerges. But
• 34:05
  let's focus on neutron stars first, because they're already bizarre enough.
• 34:11
  Picture compressing Mount Everest into a tea spoon, that's the
• 34:16
  density we're talking about. A neutron star. Is matter crush
• 34:20
  so tightly that protons and electrons merge into neutrons. The
• 34:25
  entire star becomes one giant atomic nucleus roughly twenty kilometers across,
• 34:32
  containing more mass than the Sun. The physics at these
• 34:36
  densities is extreme. Gravity is so strong that it warps
• 34:41
  space time noticeably light bends around the star. Time runs
• 34:47
  slower near the surface, and the magnetic fields. Those are
• 34:52
  in a category of their own. Some neutron stars have
• 34:56
  magnetic fields trillions of time stronger than anything we can
• 35:00
  create on Earth. These are called magnetars. Their magnetic fields
• 35:06
  are so intense they could kill you from a thousand
• 35:08
  kilometers away, not through radiation, through the magnetic field itself,
• 35:15
  distorting the electron clouds in your atoms. Neutron stars rotate fast,
• 35:22
  Some spin hundreds of times per second. This isn't random,
• 35:27
  its conservation of angular momentum. The core that collapsed was
• 35:32
  already rotating as it shrinks, its spins faster. Same principle
• 35:38
  as a figure skater pulling in their arms, except instead
• 35:42
  of a human spinning faster, you have a stellar core
• 35:46
  rotating at a significant fraction of light speed at its equator.
• 35:51
  Some neutron stars emit beams of radiation from their magnetic poles.
• 35:57
  As the star rotates, These beams deep across space, like
• 36:01
  cosmic lighthouses. When one of these beams points toward Earth,
• 36:07
  we detect regular pulses of radiation. We call these objects pulsars.
• 36:13
  They were discovered in nineteen sixty seven by Joscelyn Bell Burnell.
• 36:18
  At first the signals were so regular they were nicknamed
• 36:22
  LGM one Little Green Men. Seriously, the pulses were that precise.
• 36:30
  Turns out it wasn't aliens, just physics being weird. The
• 36:35
  material inside a neutron star exists in states we can
• 36:38
  barely describe. Near the surface, you have a crystalline crust
• 36:44
  iron nuclei packed into a rigid lattice. Deeper down, neutrons
• 36:49
  start to drip out of nuclei. Deeper still, you reach
• 36:54
  a neutron superfluid, frictionless, flowing without resistance, and at the
• 37:00
  very center we don't actually know. The pressure there exceeds
• 37:05
  anything we can recreate in laboratories. Matter might break down
• 37:09
  into quarks or form exotic states we haven't even theorized yet.
• 37:15
  Here's something that will bend your mind. Despite being incredibly dense,
• 37:20
  neutron stars aren't black holes. Light can still escape. You
• 37:25
  could theoretically stand on the surface. Well not really, you'd
• 37:30
  be crushed instantly and vaporized by radiation. But in principle,
• 37:36
  there's a surface, a place where matter exists. Unlike what's
• 37:41
  coming next, Because if the core is too massive. Even
• 37:46
  neutron degeneracy pressure can't hold it up above roughly three
• 37:50
  solar masses. There's no known force that can stop the collapse.
• 37:55
  The core doesn't stop shrinking, it doesn't bounce, It just
• 38:00
  keeps falling inward, past the point where neutrons touch, past
• 38:05
  the point where matter has any meaning, until it becomes
• 38:09
  something we can barely comprehend, a black hole. The term
• 38:14
  is misleading. Black Holes aren't holes. Their objects extremely dense objects,
• 38:21
  but they're hidden behind an event horizon, a boundary in
• 38:25
  space time beyond which nothing can escape, not matter, not light,
• 38:31
  not information. Once you cross that threshold, all paths lead inward.
• 38:38
  There's no going back. It's not a physical barrier. It's
• 38:42
  a geometric inevitability. The curvature of space time becomes so
• 38:47
  extreme that returning would require moving faster than light. What
• 38:52
  happens to the collapsing core nobody knows. General relativity predicts
• 38:58
  it forms a singularity, a point of infinite density, but
• 39:04
  infinite densities are probably unphysical. Our equations break down. We
• 39:09
  need quantum gravity to describe what really happens, and we
• 39:14
  don't have that theory yet. So the honest answer is
• 39:18
  we don't know what's at the center of a black hole.
• 39:21
  We know what's outside. We can describe the event horizon,
• 39:25
  the ergosphere, the photon sphere, but the core itself that's
• 39:31
  still a mystery. Not all black holes form from supernovae.
• 39:36
  Some form when neutron stars collide. Others grow by accreting
• 39:41
  matter over time. The black holes at the centers of
• 39:45
  galaxies probably form through mergers countless smaller black holes combining
• 39:51
  over billions of years. Our galaxy has one Sagittarius, a
• 39:56
  star four million solar masses sitting quietly at the galactic center,
• 40:03
  occasionally eating a star that wanders too close. But stellar
• 40:07
  mass black holes those formed from supernovae range from about
• 40:13
  three to one hundred solar masses, maybe more. We've detected
• 40:18
  some through gravitational waves. When two black holes orbit each other,
• 40:23
  they lose energy, the orbit decays. Eventually they merge, and
• 40:28
  when they do, they release gravitational waves ripples in space
• 40:33
  time itself. Ligo detected the first one in twenty fifteen.
• 40:39
  Two black holes, each about thirty solar masses, spiraling together.
• 40:46
  The collision released more energy than all the stars in
• 40:49
  the observable universe. Combined for a fraction of a second.
• 40:54
  That's gravitational wave astronomy, a completely new way of observing
• 40:58
  the universe. We're not using light anymore. We're detecting distortions
• 41:04
  in the fabric of space time, ripples from the most
• 41:08
  violent events in the cosmos, black hole mergers, neutron star collisions,
• 41:15
  maybe even echoes from the Big Bang itself. It's like
• 41:20
  gaining a new sense. We spent our entire history looking
• 41:25
  at the universe through light. Now we can feel it too.
• 41:29
  Neutron star collisions are particularly interesting. When two neutron stars merge,
• 41:36
  they create what's called a Kiloanova. It's similar to a supernova,
• 41:40
  but powered by different physics. The collision ejects neutron rich
• 41:45
  material at high speeds. That material undergoes rapid neutron capture.
• 41:51
  The r process. Elements heavier than iron form, gold, platinum, uranium,
• 42:00
  all the really heavy elements in the periodic table, most
• 42:04
  of them come from kilonovi. In twenty seventeen, we detected
• 42:09
  gravitational waves from a neutron star merger GW one seven
• 42:14
  eight one seven, but we also saw it in light
• 42:18
  gamma rays, X rays, visible light, infrared, radio waves. Every
• 42:24
  telescope on Earth and in space turned to look. It
• 42:28
  was the most studied astronomical event in history, and it
• 42:33
  confirmed something we'd suspected. Kilonov are the primary source of
• 42:38
  heavy elements in the universe. The gold in jewelry, the
• 42:42
  uranium in nuclear reactors. All of it was forged in
• 42:47
  neutron star collisions, scattered across space, mixed into the clouds
• 42:53
  that formed later stars and planets. You're wearing atoms from
• 42:58
  dead neutron stars. The calcium in your bones might have
• 43:02
  come from a supernova, but the iodine in your thyroid
• 43:07
  that probably came from a chilanova, two neutron stars colliding
• 43:12
  billions of years ago, creating the elements necessary for complex
• 43:17
  chemistry for biology. For you, this brings us back to
• 43:22
  supernovae because they're not just explosions. They're part of a cycle.
• 43:28
  Stars form from gas clouds. They fuse lighter elements into
• 43:33
  heavier ones, they explode, They scatter enriched material back into space.
• 43:40
  New stars form from that enriched material, and the cycle continues.
• 43:46
  Each generation of stars is slightly richer in heavy elements
• 43:50
  than the last. The first stars in the universe contained
• 43:54
  almost no heavy elements just hydrogen and helium from the
• 43:59
  Big Bang. They were massive, hundreds of solar masses. They
• 44:04
  lived fast, dyed young. Their supernovae scattered the first carbon
• 44:09
  and oxygen into space. The next generation of stars formed
• 44:14
  from slightly enriched gas. Those stars added more elements, and
• 44:19
  so it went generation after generation, the universe slowly filling
• 44:25
  with the debris of dead stars. Our Sun is a
• 44:29
  late generation star. It formed about four point six billion
• 44:33
  years ago from a cloud already rich in heavy elements.
• 44:38
  That's why we have rocky planets, why Earth exists. The
• 44:43
  first generation of stars couldn't have planets like Earth. There
• 44:47
  wasn't enough solid material, just gas. But by the time
• 44:51
  our solar system formed, there was plenty of carbon, oxygen, silicon, iron,
• 44:57
  enough to build planets, moons, ast and eventually life. Supernovae
• 45:03
  made that possible. Without them, the universe would be a
• 45:07
  simpler place. Hydrogen and helium, gas clouds, maybe some stars,
• 45:13
  but no complexity, no chemistry, no life. Every element in
• 45:18
  your body heavier than helium was created in a star.
• 45:22
  Most of those elements were scattered by supernovae. You exist
• 45:27
  because stars die violently. There's something poetic about that. Stars
• 45:32
  live for millions or billions of years, quietly fusing hydrogen
• 45:37
  into helium, then helium into carbon, carbon into oxygen, building
• 45:43
  up layers, creating heavier and heavier elements until they reach
• 45:48
  iron the end of the line, and then they die, collapse, explode,
• 45:54
  and give everything back to the universe. Ah The energy
• 45:58
  output is staggering. A typical core collapse supernova releases about
• 46:03
  ten to the forty fourth jewels of visible light. That's
• 46:08
  more energy than the Sun will emit in its entire
• 46:10
  ten billion year lifetime, released in a few weeks. But
• 46:15
  that's not even the main energy output. The neutrinos carry
• 46:19
  away far more about ten to the forty sixth jewels.
• 46:25
  Ninety nine percent of the explosion's energy leaves as neutrinos,
• 46:29
  weakly interacting particles that pass through the expanding debris almost unhindered.
• 46:36
  They stream out at nearly light speed, carrying information about
• 46:40
  the core collapse. In nineteen eighty seven, we detected neutrinos
• 46:45
  from a supernova for the first time s N nineteen
• 46:50
  eighty seven A. It exploded in the large Magellanic Cloud,
• 46:56
  a small galaxy orbiting the Milky Way about one hundred
• 47:00
  and sixty thousand light years away. Two neutrino detectors on
• 47:05
  Earth picked up the signal about twenty neutrino's total out
• 47:10
  of the ten to the fifty eight that the supernova released.
• 47:14
  That's how weekly neutrinos interact. Fifty eight orders of magnitude
• 47:19
  were created, twenty detected, but those twenty confirmed. Our models
• 47:25
  told us we understood core collapse at least roughly. The
• 47:30
  detection happened hours before the light arrived. Because neutrinos escaped immediately,
• 47:36
  light had to diffuse through the expanding debris. It took
• 47:40
  time hours or days. The neutrino's got a head start.
• 47:46
  This will be important for future supernova observations. If we
• 47:52
  detect a neutrino burst from a nearby supernova, we'll know
• 47:56
  to point our telescopes at that part of the sky
• 48:00
  before the light arrives, before the shock breaks through the surface.
• 48:05
  We might catch the shock breakout. That brief flash when
• 48:10
  the shockwave first emerges. It's one of the brightest phases,
• 48:16
  but it only lasts a few hours. Shock breakout is
• 48:19
  hard to observe. You need to be looking at the
• 48:23
  right star at exactly the right time. Most supernovae are
• 48:27
  discovered after they've already brightened. We missed the early phases,
• 48:32
  but in twenty twenty four astronomers got lucky. SN twenty
• 48:37
  twenty four g g I was caught just twenty six
• 48:42
  hours after the explosion. They pointed a telescope at it,
• 48:46
  immediately caught the shock breakout, saw the initial flash, and
• 48:50
  learn something surprising. The shockwave wasn't spherical. It was shaped
• 48:56
  like an olive stretched along one axe, compressed along another.
• 49:02
  This tells us something about the star before it exploded.
• 49:07
  Red supergiants aren't perfect spheres. Their lumpy, turbulent convection currents
• 49:14
  churn through their outer layers. The shockwave follows the path
• 49:18
  of least resistance, where the density is lower, so it
• 49:23
  breaks out asymmetrically, in this case, in an olive shape.
• 49:28
  That's new information. Our models assumed spherical explosions. Reality is messier,
• 49:34
  and that's the theme here. Reality is always more complicated
• 49:38
  than our models suggest. Supernova aren't clean. Their chaotic, asymmetric turbulent.
• 49:46
  The core doesn't collapse smoothly. It wobbles, sloshes. The shockwave stalls.
• 49:52
  Neutrinos might help revive it. Magnetic fields, twist rotation matters.
• 49:58
  Every supernova unique different mass, different composition, different rotation rate,
• 50:06
  different magnetic field. The details matter, and we're still learning
• 50:10
  what those details are. But here's where it gets even stranger.
• 50:15
  Not all supernovae follow the same path we've been talking about.
• 50:20
  Core collapse, massive stars running out of fuel, iron cores, imploding,
• 50:26
  shock waves blasting outward. That's type two and types one
• 50:32
  B and one C, which are similar but have lost
• 50:35
  their outer hydrogen layers before exploding, stripped by stellar winds
• 50:40
  or companion stars. But there's another category entirely Type one A.
• 50:48
  These don't come from massive stars at all. They come
• 50:51
  from white dwarfs. White dwarfs are stellar corpses, the remnants
• 50:56
  of stars like our sun stars that weren't massive enough
• 51:00
  to go super and nova themselves. They burn through their
• 51:03
  fuel hydrogen to helium, helium to carbon and oxygen, then
• 51:09
  stopped no more fusion. The core contracted became incredibly dense,
• 51:16
  a star's worth of mass compressed into something the size
• 51:20
  of Earth, held up not by thermal pressure but by
• 51:24
  quantum mechanics electron degeneracy pressure, Electrons packed so tightly they
• 51:30
  can't be squeezed any closer. This pressure supports the white
• 51:34
  dwarf against gravity, but there's a limit, the Chandraseca limit
• 51:39
  about one point four to four solar masses. If a
• 51:43
  white dwarf exceeds this mass, electron degeneracy pressure fails, gravity winds,
• 51:49
  the star collapses, and something remarkable happens. Most white dwarfs
• 51:55
  sit quietly, cooling slowly over billions of years, but some
• 52:01
  exist in binary systems two stars orbiting each other. If
• 52:06
  the companion is a normal star, close enough, the white
• 52:09
  dwarf can steal material, accrete it pull gas from the
• 52:13
  companion's outer layers onto itself. Slowly, over millions of years,
• 52:20
  the white dwarf gains mass, approaches the Chandrasecar limit. Or
• 52:26
  sometimes two white dwarfs orbit each other, losing energy to
• 52:30
  gravitational waves spiraling inward. Eventually they merge combine their masses
• 52:38
  exceed the limit. Either way. Once you cross one point
• 52:42
  four four solar masses, the white dwarf becomes unstable. It
• 52:46
  starts to collapse, and here's the critical difference from core
• 52:51
  collapse supernovae. White dwarfs are made of carbon and oxygen,
• 52:56
  not iron. Carbon and oxygen confuse release energy. When the
• 53:02
  white dwarf collapses, the core heats up, reaches the ignition
• 53:06
  temperature for carbon fusion, and then everything happens at Once
• 53:11
  carbon fusion begins, releases energy, heats the surrounding material, which
• 53:18
  triggers more fusion runaway reaction. The entire white dwarf becomes
• 53:23
  a nuclear bomb. No gradual burning, no layers of different elements,
• 53:29
  just instant detonation. The whole star fuses in seconds, converts
• 53:34
  to iron group elements. Nickel fifty six mostly releases enormous
• 53:40
  energy about ten to the forty fourth duels, similar to
• 53:44
  core collapse, but the mechanism is completely different. The white
• 53:49
  dwarf is completely destroyed, nothing left behind, No neutron star,
• 53:55
  no black hole, just expanding debris moving at ten thousand
• 54:00
  kilometers per second six percent light speed, slightly slower than
• 54:06
  core collapse ejector, but still incredibly fast. Type one A
• 54:12
  supernova are important for cosmology because they're remarkably consistent. Every
• 54:18
  Type one A has roughly the same peak brightness, about
• 54:22
  five billion times brighter than the sun. This makes them
• 54:27
  standard candles. If you know how bright something is intrinsically,
• 54:33
  and you measure how bright it appears, you can calculate
• 54:37
  its distance simple inverse square law. Astronomers use type one
• 54:43
  A supernova to measure distances across the universe billions of
• 54:49
  light years, far beyond where other methods work. This is
• 54:53
  how we discover dark energy. In the late nineteen nineties,
• 54:58
  two teams study distant Type one A supernovae. Expected to
• 55:04
  see the universe's expansions slowing down, gravity pulling everything back together,
• 55:10
  But they found the opposite. The expansion was accelerating. Distant
• 55:16
  supernovae were dimmer than expected, farther away than they should be.
• 55:22
  Something was pushing the universe apart. We call it dark energy.
• 55:28
  Still don't understand what it is, but Type one A
• 55:32
  supernovae revealed its existence. Though even Type one A aren't
• 55:38
  perfectly uniform. There's scatter, Some are brighter, some dimmer. Astronomers
• 55:45
  have learned to correct for this, standardize them. Use the
• 55:49
  light curve shape how quickly they brighten and fade. Brighter
• 55:54
  ones fade slower, dimmer ones fade faster. There's a relationship.
• 56:00
  You can measure the light curve, apply corrections, get a
• 56:04
  more accurate standard candle, and recently we've found exceptions. Super Chandrasekhar.
• 56:10
  Supernova type one A events that seem to come from
• 56:15
  white dwarfs exceeding one point four to four solar masses,
• 56:20
  some up to two point four solar masses. How we're
• 56:24
  not sure, maybe rapid rotation, centrifugal force providing extra support,
• 56:30
  or strong magnetic fields adding pressure. These are rare, but
• 56:35
  they exist, and they challenge our models. What happens after
• 56:40
  a supernova? The star is gone destroyed, but it leaves
• 56:45
  something behind, a remnant. For type one A, it's just
• 56:50
  expanding debris, gas and dust spreading into space. But for
• 56:55
  core collapse, there's also the core, the collapsed remnant. If
• 57:01
  the original star was between about eight and twenty solar masses,
• 57:05
  the core becomes a neutron star, something extraordinary. The core
• 57:10
  collapses until neutrons themselves provide degeneracy pressure similar to electron
• 57:16
  degeneracy in white dwarfs, but at even higher density. A
• 57:22
  neutron star contains about one point four solar masses compressed
• 57:26
  into a sphere twenty kilometers across. A city sized ball
• 57:31
  of neutrons, density beyond comprehension. A tea spoon of neutron
• 57:36
  star material would weigh a billion tons on Earth. Neutron
• 57:41
  stars are laboratories for extreme physics. Gravity so strong it
• 57:46
  warps spacetime noticeably. Magnetic fields are trillion times earths. Some
• 57:52
  neutron stars spin hundreds of times per second pulsars. We
• 57:57
  detect them as rhythmic pulses of radio waves lighthouse beams
• 58:02
  sweeping across space incredibly precise. Some pulsars keep time better
• 58:08
  than atomic clocks. But if the core is massive enough,
• 58:12
  even neutron degeneracy can't hold it up. Above about three
• 58:16
  solar masses, nothing can stop the collapse. The core shrinks
• 58:21
  to zero volume infinite density, a singularity surrounded by an
• 58:28
  event horizon. A black hole forms the ultimate end point
• 58:34
  where matter disappears from the observable universe, falls into a
• 58:39
  region where even light can't escape. We think most massive
• 58:43
  stars above about twenty solar masses leave black holes. Smaller
• 58:49
  ones leave neutron stars. The boundary isn't sharp depends on
• 58:55
  mass loss during the star's life, how much material was
• 58:59
  blown away by by winds, whether it had a companion
• 59:02
  stripping mass. The final core mass determines the remnant. Either way,
• 59:08
  the explosion itself creates a supernova remnant the expanding debris
• 59:14
  from the star's outer layers. This material plows into the
• 59:18
  surrounding interstellar medium, sweeps it up, creates a shock wave.
• 59:24
  The remnant grows hundreds of light years across, eventually glowing
• 59:30
  in X rays and visible light. We can see many
• 59:34
  of them in our galaxy. The crab Nebula is a
• 59:37
  famous example remnant of s N one thousand fifty four,
• 59:41
  the supernova Chinese astronomers recorded in July one thousand fifty four.
• 59:47
  It appeared in the constellation Taurus, bright enough to see
• 59:51
  during the day, visible for twenty three days in daylight
• 59:56
  six hundred fifty three days at night, then faded, but
• 1:00:00
  it left behind a glowing cloud, still expanding today, still
• 1:00:07
  visible through telescopes. At its center a pulsar spinning thirty
• 1:00:13
  times per second. The collapsed core Cassiopeia A is another
• 1:00:20
  younger exploded about three hundred forty years ago, but we
• 1:00:24
  don't have historical records. It should have been visible bright enough,
• 1:00:29
  but no one recorded. It. May be obscured by dust,
• 1:00:33
  or maybe we just missed it happens, the remnant is spectacular,
• 1:00:40
  one of the brightest radio sources in the sky. Expanding
• 1:00:44
  at thirteen million miles per hour, fastest supernova shock wave.
• 1:00:49
  We know. These remnants are crucial there where the heavy
• 1:00:53
  elements mix into space, carbon, oxygen, silicon, iron, all forged
• 1:01:00
  in the star's core blusted outward by the explosion. Eventually
• 1:01:05
  this material will be incorporated into new stars, new planets us.
• 1:01:11
  Every atom in your body heavier than helium came from
• 1:01:14
  a star, most from supernovae. You're made of star dust literally.
• 1:01:21
  Supernova remnants also accelerate cosmic rays, high energy particles that
• 1:01:26
  zip through space at nearly light speed Protons, mostly some
• 1:01:30
  heavier nuclei. They bombard Earth constantly. We're not sure exactly
• 1:01:36
  how supernovae accelerate them, something to do with the shock
• 1:01:40
  waves magnetic fields, particles bouncing back and forth across the shock,
• 1:01:47
  gaining energy each time, eventually reaching enormous energies. Some cosmic
• 1:01:53
  rays have energies equivalent to a baseball traveling sixty miles
• 1:01:57
  per hour concentrated in a single proton. We don't know
• 1:02:02
  how that's possible, but supernova are the leading candidates. The
• 1:02:08
  remnants can also trigger new star formation if the expanding
• 1:02:13
  shock wave encounters a molecular cloud it compresses the gas density, increases,
• 1:02:20
  gravity takes over regions collapse form new stars. So supernova
• 1:02:26
  seed their own replacements, one generation dying, enriching the galaxy,
• 1:02:32
  triggering the next generation. Our Sun might have formed this way.
• 1:02:37
  There's evidence meteorites contain isotopes that decay quickly aluminum twenty six,
• 1:02:44
  iron sixty. They shouldn't still exist. They should have decayed
• 1:02:49
  billions of years ago, unless they were created recently, just
• 1:02:53
  before the Solar System formed. Supernova produce these isotopes. The
• 1:02:59
  theory is the nearby supernova exploded shock wave hit a
• 1:03:03
  molecular cloud, compressed it, triggered collapse, and injected freshly made isotopes.
• 1:03:10
  The Sun and planets formed from that enriched material. We're
• 1:03:14
  here because of a supernova possibly. How often does supernova
• 1:03:19
  happen in our galaxy? About one every fifty years on average,
• 1:03:25
  But they're not evenly distributed, Sometimes centuries pass, sometimes multiple
• 1:03:30
  in a decade, and most are hidden. Our galaxy is dusty,
• 1:03:35
  especially toward the center. Dust blocks visible light. We can't
• 1:03:41
  see most of the galaxy optically. We rely on radio
• 1:03:44
  and infrared X rays, wavelengths that penetrate dust. The last
• 1:03:50
  visible supernova in the Milky Way was sixteen oh four
• 1:03:54
  Kepler's supernova, before telescopes existed. Johannes Kepler observed it, recorded
• 1:04:00
  its brightness position. It faded after a year. Since then
• 1:04:06
  nothing four hundred twenty years. We're overdue statistically, though, that
• 1:04:12
  doesn't mean one is imminent. Random processes don't work that way.
• 1:04:17
  But we have seen supernovae in nearby galaxies. Thousands, tens
• 1:04:22
  of thousands automated surveys scan the sky nightly looking for
• 1:04:27
  new points of light transience. Most are supernovae. We discover
• 1:04:34
  hundreds every year. Now study their spectra, light curves, learn
• 1:04:39
  about different types, progenitors, mechanisms, and we've learned something surprising.
• 1:04:47
  There's more variety than we thought. Superluminous supernovae a hundred
• 1:04:52
  times brighter than normal. We're not sure what causes them.
• 1:04:57
  May be pair instability In very massive stars, gamma rays
• 1:05:03
  becomes so energetic they create electron positron pairs, reduces pressure,
• 1:05:09
  core collapses, triggers massive thermonuclear explosion completely destroys the star.
• 1:05:16
  No remnant or maybe magnetars Neutron stars with extreme magnetic
• 1:05:22
  fields spinning rapidly, releasing energy powering the light. Super and
• 1:05:28
  ov impostors stars that brighten like super and Ova, then fade,
• 1:05:34
  then do it again. Etacarrine is the most famous. It
• 1:05:38
  erupted in the eighteen forties, became one of the brightest
• 1:05:41
  stars in the sky, then faded but didn't explode. Still there,
• 1:05:48
  still massive, about one hundred solar masses, probably unstable. Might
• 1:05:54
  actually explode someday or might not. We're watching calcium rich transients,
• 1:06:01
  faint supernova rich in calcium found far from galaxies in
• 1:06:07
  intergalactic space. We don't understand them. White dwarfs maybe, but
• 1:06:13
  the locations are strange. The more we observe, the more
• 1:06:16
  complexity we find. Supernovae aren't one phenomenon. They're a family,
• 1:06:23
  different mechanisms, different progenitors, different outcomes. The universe is creative,
• 1:06:32
  finds many ways to explode stars, and we're still cataloging them,
• 1:06:39
  still trying to understand. Let's talk about s N nineteen
• 1:06:43
  eighty seven, a February twenty third, nineteen eighty seven Ian
• 1:06:49
  Shelton astronomer working at Las Campanas Observatory in Chile, photographing
• 1:06:55
  the large Magellanic Cloud small satellite galaxy orbits. The Milky Way,
• 1:07:01
  about one hundred sixty thousand light years away. He developed
• 1:07:06
  the photographic plate, noticed something, a bright spot wasn't there before,
• 1:07:12
  checked previous images, definitely new. He stepped outside, looked up,
• 1:07:18
  saw it with his naked eye. A supernova visible without
• 1:07:23
  a telescope, first one since sixteen oh four. The news
• 1:07:27
  spread fast, Telescopes worldwide turned toward it. Observatories scrambled. Everyone
• 1:07:34
  wanted data. This was unprecedented, a nearby supernova in the
• 1:07:39
  modern era. With modern instruments spectroscopes, CCD cameras, radio telescopes,
• 1:07:46
  neutrino detectors, we could study it properly, not just sketch
• 1:07:51
  its position, actually measure, analyze, understand, and it delivered s
• 1:07:58
  N nineteen eighty six A taught us more about supernova
• 1:08:04
  than any observation before it, maybe since two. Here's what
• 1:08:08
  made it special. The progenitor star was identified Sandulique negative
• 1:08:14
  sixty nine degrees two hundred two, a blue supergiant about
• 1:08:18
  twenty solar masses. We had images of it from before
• 1:08:22
  the explosion. We knew what it was. This was new.
• 1:08:27
  Usually we arrive after star already gone, debris expanding, But
• 1:08:33
  here we had before and after we could compare confirm theories.
• 1:08:39
  The light curve was strange. It brightened, then plateaued, then
• 1:08:43
  brightened again, not the smooth rise and fall we expected.
• 1:08:48
  Turns out the star had a complex history. It was
• 1:08:51
  born as a blue supergiant, then evolved into a red supergiant, expanded,
• 1:08:57
  then contracted back became blue again. Just before it exploded,
• 1:09:03
  the extended envelope from its red phase was still there
• 1:09:08
  surrounding the core. When the shock wave hit this envelope,
• 1:09:13
  it created the unusual light curve multiple peaks. We learned
• 1:09:17
  something stellar evolution isn't smooth. Stars change, contract expand interact
• 1:09:25
  with their own past. And then there were the neutrinos.
• 1:09:29
  Three detectors caught them, Cameo Kande in Japan, IMB in
• 1:09:34
  the United States, Baksen in Russia, water based detectors designed
• 1:09:40
  to catch rare interactions newtrinos passing through colliding with protons,
• 1:09:46
  creating flashes of light. On February twenty third, they all
• 1:09:50
  registered a burst twelve neutrinos at Cameocande, eight at IMB,
• 1:09:57
  five at Baksan within thirty seconds from the same direction
• 1:10:03
  large magellanic cloud. Three hours before the optical light arrived.
• 1:10:08
  This confirmed theory. Neutrinos escape first, they're weakly interacting. Pass
• 1:10:14
  through the star light takes longer trapped in the dense material,
• 1:10:19
  scattering diffusing outward. Eventually breaks free, but hours later. The
• 1:10:26
  neutrino detection was monumental. It proved core collapse releases most
• 1:10:32
  energy as neutrinos, about ten to the fifty three ergs,
• 1:10:36
  almost all carried by neutrinos. Only one percent becomes light
• 1:10:42
  kinetic energy, the visible explosion, the rest invisible ghosting through
• 1:10:48
  the universe. We also learned about neutrino physics. The burst
• 1:10:53
  arrived over thirteen seconds, not instantaneously. This told us something.
• 1:10:59
  Netrino's have mass very small but not zero. Massless particles
• 1:11:05
  travel at light speed. All arrive together, but if they
• 1:11:08
  have mass slightly slower, different energies, different speeds, small delays
• 1:11:16
  measurable over one hundred and sixty thousand light years. From
• 1:11:20
  those thirteen seconds, we calculated neutrino mass less than a
• 1:11:25
  few electron vaults, tiny but not nothing. One supernova. Three
• 1:11:31
  neutrino detectors a new field born neutrino astronomy. Now we
• 1:11:36
  watch for them always. Detectors running waiting for the next one,
• 1:11:42
  because neutrinos arrive first early warning system. If we detect
• 1:11:47
  a burst, we know supernova happening somewhere. Point telescopes fast
• 1:11:53
  catch the shop breakout. The earliest light SN nineteen eighty
• 1:11:58
  seven A also revealed rings, not immediately took months. As
• 1:12:03
  debris expanded, it illuminated surrounding material gas dust ejected by
• 1:12:10
  the star thousands of years earlier during its red giant phase.
• 1:12:15
  Stellar wind blown outward formed a structure, an hour glass,
• 1:12:20
  two lobes connected by a ring equatorial. The supernova lit
• 1:12:26
  it up like a cosmic flashlight, ultraviolet radiation ionizing the gas,
• 1:12:33
  making it glow. We watched the ring brighten over years, decades.
• 1:12:39
  It's still visible, still evolving. The shockwave reached the ring
• 1:12:43
  around two thousand, thirteen years after the explosion, impact compression
• 1:12:49
  heating new emission X rays. The ring started changing, brightening,
• 1:12:55
  developing hotspots, knots, dense clumps getting hit radiating. We're still
• 1:13:01
  observing it Hubble Chandra Alma watching the interaction how shock
• 1:13:06
  waves heat, gas transfer energy. It's a laboratory, real time
• 1:13:11
  astrophysics unfolding over decades, and we're learning about circumstellar material,
• 1:13:17
  mass loss, stellar winds, how stars shed mass before they die.
• 1:13:24
  SN nineteen eighty seven A also had a mystery. The
• 1:13:29
  compact object core collapse should leave something neutron star or
• 1:13:35
  black hole. We've looked hard, no pulser detected, no X
• 1:13:41
  ray signature. Maybe it's there hidden, buried in dust debris
• 1:13:46
  blocking our view. Or maybe it formed a black hole directly.
• 1:13:51
  No bounce, just collapse straight through. We don't know the
• 1:13:56
  missing remnant still unsolved thirty seven years left, but there
• 1:14:01
  are hints recent observations Alma infrared. A blob center of
• 1:14:07
  the remnant could be dust warm dust heated by something
• 1:14:12
  compact object, maybe accreting material generating heat, or could be
• 1:14:17
  radioactive decay isotopes still glowing. We're not sure. The data
• 1:14:23
  is ambiguous. We need more, better resolution, longer wavelengths James
• 1:14:29
  Web maybe or future telescopes extremely large telescope coming online
• 1:14:35
  soon might resolve it. Find the core, solve the mystery
• 1:14:40
  s n nineteen eighty seven. A keeps teaching us even now.
• 1:14:46
  It's a gift, a nearby explosion, well documented, monitored continuously.
• 1:14:52
  We'll study it for generations. Compare models, test theories understand physics,
• 1:14:58
  extreme conditions, de densities, temperatures, magnetic fields. Nothing else comes close.
• 1:15:05
  But what about the future. Could a supernova threaten Earth?
• 1:15:09
  It's possible theoretically if one exploded close enough, within thirty
• 1:15:15
  light years, maybe the radiation gamma rays X rays could
• 1:15:20
  damage our atmosphere, strip the ozone layer, increase UV exposure
• 1:15:25
  harm life, or the cosmic rays high energy particles accelerated
• 1:15:31
  by the shock bombarding Earth for centuries, affecting climate, causing mutations,
• 1:15:38
  mass extinctions. Even some researchers think this happened. Past extinctions
• 1:15:44
  correlate with supernova timing isotopes in rock layers. Iron sixty
• 1:15:50
  doesn't occur naturally, comes from supernova found in ocean sediments
• 1:15:56
  two million years ago. Evidence of a nearby explosion Scorpius
• 1:16:01
  Centaurus association group of stars about four hundred light years away.
• 1:16:07
  One of them exploded close enough deposited iron sixty on Earth.
• 1:16:14
  Did it affect life? Hard to say. The Pliocene epoch
• 1:16:19
  climate changes, some species disappeared coincidence maybe or cause an effect.
• 1:16:26
  We don't know, but currently we're safe. No massive stars nearby.
• 1:16:32
  Beetlejuice is close six hundred fifty light years will explode someday,
• 1:16:38
  could be tomorrow, could be one hundred thousand years, but
• 1:16:41
  it's far enough. Won't hurt us, Just spectacular brighten the
• 1:16:46
  sky visible during the day, outshine the moon for weeks,
• 1:16:52
  maybe months, then fade gradually over years, leaving a nebula
• 1:16:59
  expanding remnant. Future astronomers hundreds of years from now will
• 1:17:05
  study it like we study Cassio payer a crab nebula,
• 1:17:10
  but will see it happen live real time. What would
• 1:17:14
  it look like? Predictions vary, brightness, duration, color, beetle jewice
• 1:17:20
  is red, cooler star. The supernova might have a reddish
• 1:17:24
  hue initially, then blue white as it heats up the
• 1:17:29
  light curve, rise and fall over months. We'd track it spectroscopy,
• 1:17:35
  measure composition, expansion, velocity, asymmetries. It would dominate astronomy for years,
• 1:17:42
  every telescope pointed at it, professional, amateur students, everyone, A
• 1:17:50
  once in civilization event and its coming question is when
• 1:17:55
  could you see a supernova right now? Probably with a telescope.
• 1:18:00
  They happen constantly in distant galaxies. Automated surveys fine dozens weekly,
• 1:18:06
  Zwiki Transient Facility ZTF scans the sky every night, compares images,
• 1:18:13
  looks for changes, new points brightening. Most are supernova thousands
• 1:18:19
  discovered every year, classified spectra taken, redshifts measured, distances calculated,
• 1:18:26
  added to databases available to researchers worldwide. This is modern astronomy,
• 1:18:32
  big data, automated, fast within hours, discovery, classification, follow up,
• 1:18:39
  coordinated telescopes around the world, space based, ground based, different wavelengths, optical, infrared, ultraviolet,
• 1:18:50
  X ray, radio, full picture, multi wavelength. The data is
• 1:18:55
  staggering light curves tea housands of them, each one unique,
• 1:19:01
  slightly different, different progenitors, masses, compositions, environments. We analyze them statistically,
• 1:19:10
  look for patterns, correlations, brightness versus decay rate, spectra versus
• 1:19:17
  peak luminosity. This is how we refine models, test predictions,
• 1:19:23
  understand diversity and diversity. There is Supernovae come in flavors.
• 1:19:30
  We've mentioned types IA two IBIC, but within those subtypes
• 1:19:37
  two P plateau flat light curve, two L linear steady decline,
• 1:19:43
  two B shows helium, two N narrow lines interacts with
• 1:19:48
  circumstellar material. Each tells a story, different progenitor, different death,
• 1:19:53
  different physics. Type one A are the strangest thermonuclear white
• 1:19:59
  dwarf cretees matter reaches critical mass one point four solar
• 1:20:04
  masses chandrasecar limit, carbon ignites runaway, fusion, entire star obliterated,
• 1:20:11
  no remnant, just debris expanding, glowing, powered by radioactive decay
• 1:20:17
  nickel fifty six, cobalt fifty six, iron fifty six. This
• 1:20:21
  decay produces light. The glow for months. The light curve
• 1:20:26
  very consistent. Type one A all similar, same mass, same explosion,
• 1:20:33
  same brightness, peak luminosity known makes them standard candles measure
• 1:20:40
  apparent brightness, calculate distance. This is how we discovered dark energy.
• 1:20:46
  Nineteen ninety eight. Two teams study in distant Type one
• 1:20:51
  A expected them to be certain brightness, but they were dimmer,
• 1:20:56
  farther away than predicted. Universe expanding faster, accelerating, not slowing
• 1:21:03
  as expected. Gravity should decelerate, pull everything back, but no
• 1:21:10
  expansion speeding up. Something pushing dark energy, mysterious, unexplained, makes
• 1:21:17
  up seventy percent of the universe. We don't know what
• 1:21:21
  it is, just that it's there. Accelerating expansion supernovae told
• 1:21:28
  us this Type one A standard candles revealed the universe's fate.
• 1:21:34
  It will expand forever, faster galaxies receding eventually beyond our horizon,
• 1:21:42
  unreachable universe becoming emptier, colder, darker, heat death trillions of
• 1:21:49
  years from now, but certain unless something changes. Dark energy
• 1:21:54
  evolves unlikely but possible. We're still measuring more supernovae, better data,
• 1:22:00
  refining models, Understanding acceleration, how it changes over time. The
• 1:22:06
  equation of state of dark energy critical parameter tells us
• 1:22:11
  future fate. Everything and supernova are the key. They probe
• 1:22:17
  cosmic history. Expansion rate at different epochs near far, early
• 1:22:23
  universe recent. Build a timeline map expansion. Understand dark energy.
• 1:22:28
  This is cosmology driven by explosions, stellar deaths across billions
• 1:22:34
  of years light reaching us now from when universe was
• 1:22:40
  young half its current age. Third, we measure compare, learn
• 1:22:46
  the Universe's story written in supernovae. But there's something else,
• 1:22:51
  something we haven't touched. The sound. You can't hear explosions
• 1:22:56
  in space. No medium sound needs air, molecule vibrating transmitting
• 1:23:01
  pressure waves. Space is vacuum, empty, silent, but supernova create
• 1:23:07
  pressure waves in gas nebulae surrounding material. These waves travel
• 1:23:13
  compress heat. We can detect them. Radio telescopes measure density, fluctuations,
• 1:23:19
  map them convert to sound. Soonification NASA does this, takes
• 1:23:24
  data X ray, radio infrared maps brightness, position over time,
• 1:23:30
  converts to audio pitch, volume, tone. You can listen to
• 1:23:36
  supernova remnants Cassiopaya, a crab nebula. They have voices, eerie, haunting, beautiful, whistles, rumbles, tones, rising, falling.
• 1:23:50
  It's not real sound, not what you'd hear if you
• 1:23:53
  were there, because you'd hear nothing, but it represents the data,
• 1:23:58
  the physics waves propagating, energy, distributing, structure forming, and it's moving, emotional,
• 1:24:05
  even to hear the death cry of a star translated
• 1:24:11
  into something we can perceive. Our brains process sound differently
• 1:24:16
  than images, patterns, rhythms, changes, We notice things we'd miss
• 1:24:22
  in pictures. Soonification is at aol scientific but also artistic, communicative.
• 1:24:29
  It brings the universe closer, makes it relatable human because
• 1:24:35
  these events, supernovae, they're violent, destructive, cataclysmic, but also creative, generative, beautiful.
• 1:24:44
  They end and begin, destroy and create, death and birth
• 1:24:50
  all at once, and we're drawn to that, the duality.
• 1:24:54
  We understand it instinctively. Everything in life carries this tension,
• 1:24:59
  end that seed beginnings, loss that enables gain. Supernova embody
• 1:25:05
  this truth on cosmic scale. But let's talk about something
• 1:25:10
  we haven't fully explored. The observers, the humans who study
• 1:25:14
  these events, the astronomers staring into darkness, waiting, hoping for
• 1:25:21
  stars to die. It sounds morbid, maybe it is, but
• 1:25:25
  it's also essential because supernova don't announce themselves. They just
• 1:25:30
  happen somewhere in some galaxy among billions of stars. One goes,
• 1:25:37
  and if we're not watching, we miss it. Gone, The
• 1:25:41
  light fades, evidence disappears, opportunity lost. So astronomers scan every night,
• 1:25:48
  automated telescopes surveys, photographing patches of sky, repeatedly comparing images,
• 1:25:55
  looking for changes, new points of light where there was
• 1:26:00
  nothing before. It's tedious, computational mostly algorithms flag potential candidates,
• 1:26:07
  then humans check, confirm, classify, measure, follow up. Some nights, nothing, weeks, months,
• 1:26:16
  then alert new transient brightening rapidly could be supernova, could
• 1:26:22
  be something else, asteroid, variable, star camera glitch. Cosmic ray
• 1:26:27
  needs verification. Spectroscopy reveals the truth. Elements present, velocities, expansion, temperature,
• 1:26:35
  the signature unmistakable, it's a supernova, and the clock starts.
• 1:26:41
  Because supernovae evolve quickly. At first, the light curve rises, peaks,
• 1:26:48
  then declines different rates, depending on type. Type one a
• 1:26:54
  rise in weeks, peak, stay bright month or so, then
• 1:26:58
  fade gradually over months, powered by radioactive decay. Predictable type
• 1:27:05
  two more varied summrise fast, peak, quickly fade faster. Others plateau,
• 1:27:12
  stay bright longer, then drop. Each one unique, but patterns emerge.
• 1:27:18
  Classifications help, but observation is everything. The more data, the better.
• 1:27:25
  Multiple wavelengths X ray, ultraviolet, optical, infrared, radio, each reveals
• 1:27:32
  different physics, different layers, different processes, shock, heating, radioactive glow,
• 1:27:38
  dust formation, interaction with surrounding material, all happening simultaneously, overlapping,
• 1:27:46
  competing creating the signal we observe, and timing matters. Early
• 1:27:52
  observations crucial. The first hours days capture processes we can't
• 1:27:58
  see later, the shock breakout, That initial flash when the
• 1:28:03
  shock wave bursts through the star's surface, its brief hours
• 1:28:08
  at most mostly X ray ultraviolet difficult to catch, requires
• 1:28:13
  luck and fast response. S N twenty twenty four GGI
• 1:28:19
  court early just twenty six hours after first detection. Yang
• 1:28:24
  astronomer pointed the VLT very large telescope at it immediately
• 1:28:30
  got spectra imaging captured. The early evolution saw something remarkable.
• 1:28:37
  The explosion wasn't spherical. It was olive shaped, elongated, asymmetric.
• 1:28:43
  The progenitor red supergiant twelve to fifteen solar masses radius
• 1:28:49
  five hundred times the sun huge, and when it exploded,
• 1:28:53
  the blast emerged unevenly, not uniform, one direction, stronger faster
• 1:29:01
  than others. Why we don't know exactly. Maybe rotation, magnetic fields,
• 1:29:07
  asymmetries in the core convection instabilities. Stars aren't perfect spheres
• 1:29:14
  inside their turbulent, roiling convective cells rising, falling, mixing, and
• 1:29:20
  when they collapse that chaos amplifies. The core bounces, but
• 1:29:26
  not symmetrically. The shock propagates irregularly. Jets can form matter
• 1:29:32
  streams outward, preferentially along poles or equators, depending on conditions.
• 1:29:40
  We're learning that asymmetry is common, not the exception. Most
• 1:29:45
  supernovae are lopsided to some degree. We see it in
• 1:29:49
  remnants Cassiopayer, a clearly asymmetric debris moving faster one side
• 1:29:57
  than the other knots filaments, jets all evidence of complex
• 1:30:03
  explosion geometry, and this matters for understanding the mechanism. How
• 1:30:09
  exactly does the shock revive after stalling in core collapse.
• 1:30:15
  It's a problem. The bounce shock loses energy, dissociates nuclei
• 1:30:20
  into protons, neutrons, endothermic absorbs energy. Shock weakens, stalls at
• 1:30:27
  a few hundred kilometers from the core. Sohow does it restart,
• 1:30:33
  break through, eject the star neutrinos? The answer probably the
• 1:30:39
  core collapses into neutron star or black hole. Incredibly hot
• 1:30:45
  radiating neutrinos trillions per second ten to the fifty eight
• 1:30:50
  in total. Most escape straight through everything, but a tiny fraction,
• 1:30:56
  maybe one percent less interacts matter behind the shock, deposits energy,
• 1:31:03
  heats it drives convection turbulence, and this revives the shock,
• 1:31:09
  pushes it outward explodes the star. This is the theory
• 1:31:14
  neutrino driven explosion, supported by simulations three dimensional models showing
• 1:31:25
  how convect iron turbulence asymmetry help the shock succeed, But
• 1:31:32
  we're not certain. Observations of neutrinos from supernova Rare SN
• 1:31:39
  nineteen eighty seven A only one detected, with neutrinos twenty
• 1:31:44
  five events total from two detectors in nineteen eighty seven
• 1:31:49
  supernova in large Magellanic cloud one hundred sixty thousand light
• 1:31:53
  years away close for supernova, and we detected neutrinos hours
• 1:31:59
  before optical signal. Because neutrinos escape immediately cor collapse happens,
• 1:32:06
  neutrinos stream out light speed through the star out into space.
• 1:32:12
  Light trapped inside dense envelope takes time to diffuse hours days,
• 1:32:19
  eventually breaks free. We see it, but neutrinos already gone
• 1:32:24
  arrived earlier. This is powerful early warning system. If we
• 1:32:29
  detect neutrino burst from direction in sky, we know supernova
• 1:32:36
  happening right now. Point telescopes immediately catch the rise, the
• 1:32:42
  breakout everything. Future neutrino detectors larger, more sensitive ice cube
• 1:32:49
  at South Pole detecting high energy neutrinos, not supernova energy range,
• 1:32:56
  but others. Hypercameo Cande in Japan, successor two super Cameo
• 1:33:01
  Kanda bigger better. We'll detect galactic supernova easily, thousands of neutrinos.
• 1:33:08
  If one goes off in Milky Way, we'll know immediately
• 1:33:12
  alert the world. Every telescope turns watches. It'll be incredible
• 1:33:18
  once in lifetime event for astronomy. The last galactic supernova
• 1:33:23
  visible to naked eye was sixteen O four Keplers supernova,
• 1:33:29
  over four hundred years ago. We're overdue. Statistically, Milky Way
• 1:33:35
  should have a few per century. We haven't seen one
• 1:33:39
  in four centuries. They've happened, probably just on far side
• 1:33:46
  galaxy hidden by dust obscured. We can't see through galactic
• 1:33:53
  plane thick with gas. Dust blocks optical light, but infrared
• 1:33:59
  radio X ray penetrate. We've found remnants recent relatively Cassiopea
• 1:34:06
  A exploded around sixteen eighty approximately, but no record of observation.
• 1:34:12
  Too faint or hidden or missed. Unlucky. When will the
• 1:34:16
  next galactic supernova occur? We don't know. Could be tomorrow,
• 1:34:22
  could be one hundred years, could be thousand, random, unpredictable,
• 1:34:27
  but candidates exist. Beetlejuice, famous red super giant in Orion
• 1:34:33
  ten to twenty solar masses approaching end of life. Could
• 1:34:38
  explode any time next million years or tomorrow. We don't
• 1:34:44
  know exactly. Its mass uncertain, evolutionary state unclear, It's variable.
• 1:34:51
  Dims brightons in twenty nineteen dimmed dramatically. Speculation was it
• 1:34:59
  going supernova? No turned out, dust cloud ejected material, blocking light. Temporarily,
• 1:35:06
  it recovered beetlejuice is still there for now, but someday
• 1:35:11
  it will explode, and when it does, it'll be spectacular
• 1:35:15
  visible daytime, bright as quarter moon, maybe brighter, depending on details.
• 1:35:22
  It's only six hundred and fifty light years away, approximately
• 1:35:27
  close cosmically speaking, safe for Earth, far enough radiation won't
• 1:35:33
  harm us, but close enough to study in detail every wavelength,
• 1:35:38
  every instrument pointed at it, learning everything we can about
• 1:35:44
  core collapse in real time. Imagine that the data, the
• 1:35:49
  insights it would revolutionize our understanding supernova physics, stellar evolution, nucleosynthesis, everything,
• 1:36:00
  And it's coming someday, we just don't know when. Meanwhile,
• 1:36:03
  we watch other galaxies, distant stars dying millions billions light
• 1:36:09
  years away, their light reaching us now, from when universe
• 1:36:15
  was younger. We're seeing the past, learning history of stars
• 1:36:20
  across time. Supernova in young galaxies, different metallicity, lower, fewer
• 1:36:27
  heavy elements, stars formed from more primordial gas, hydrogen, helium,
• 1:36:34
  little else. These stars burn differently, explode differently. Maybe we're
• 1:36:39
  testing models predictions against observations. James Webb Space Telescope found
• 1:36:47
  super nova from when universe only seven hundred and thirty
• 1:36:51
  million years old. Sn in GRB two five zero three
• 1:36:56
  one four A associated with gamma burst extremely energetic long
• 1:37:03
  duration burst sign of massive star collapse and web detected
• 1:37:09
  it imaged host galaxy measured properties. This is era of reionization,
• 1:37:15
  first stars, galaxies emerging, ionizing neutral hydrogen filling universe. Supernovae
• 1:37:23
  played role in this, enriching gas with metals, oxygen, carbon, iron,
• 1:37:29
  seeding next generation stars, planets, life. Eventually, these ancient supernovae
• 1:37:35
  our ancestors to everything we see today, including us. The
• 1:37:41
  iron in your blood forged in supernova billions of years ago,
• 1:37:46
  ejected into space, mixed with gas, collapsed into new star sun,
• 1:37:53
  Planets formed, Earth cooled, life emerged evolved. Here. You are
• 1:38:00
  made of star dust, literally supernova ash. It's poetic but
• 1:38:06
  also factual. Carl Sagan said it, we are star stuff
• 1:38:11
  contemplating stars, and he was right. Every atom heavier than
• 1:38:17
  helium in your body came from stellar nucleosynthesis, most from supernova.
• 1:38:22
  The calcium in bones, oxygen you breathe, carbon in DNA,
• 1:38:27
  nitrogen in proteins, phosphorus, sulfur, all forged in stars dispersed
• 1:38:34
  by explosions. Supernova are not just destruction. Their creation engines,
• 1:38:40
  cosmic recycling, plants, death gives life. Literally Without supernova, no
• 1:38:46
  heavy elements, no planets, no chemistry complex enough for life.
• 1:38:52
  Universe would be hydrogen helium, boring, sterile, dark, but supernova
• 1:38:58
  change that enriched cosmos made diversity possible, and they continue.
• 1:39:04
  Every supernova adds to the galactic inventory metals, slowly increasing
• 1:39:13
  metallicity over time. Early universe low metallicity, now higher. Sun
• 1:39:20
  has about two percent metals by mass rest hydrogen helium,
• 1:39:26
  but that two percent critical planets formed from it. Life
• 1:39:32
  depends on it, and it's all from stars dyeing, exploding,
• 1:39:37
  scattering their guts across space and time. This cycle continues,
• 1:39:42
  will continue as long as stars form die billions of
• 1:39:47
  years into future, until star formation ceases. Eventually universe expands
• 1:39:54
  too much, galaxies isolated, gas depleted, used up, no more
• 1:39:59
  stars form, Existing stars burnout, die, white dwarfs, neutron stars,
• 1:40:05
  black holes left behind, cold dark remnants, no more supernova,
• 1:40:10
  no more light, just darkness expanding forever, heat death, trillions
• 1:40:16
  of years away but inevitable unless something changes. We don't
• 1:40:22
  expect it. Two dark energy accelerating expansion, continuing Universe headed
• 1:40:28
  toward cold, empty end. Supernova told us this type one
• 1:40:35
  A standard Candles measured distances red shifts discovered acceleration nineteen
• 1:40:43
  ninety eight, Nobel Prize twenty eleven saw Pearl Mutter, Brian
• 1:40:48
  Schmidt Adam Reese recognized for this discovery changed cosmology forever.
• 1:40:55
  Before we thought universe might recollapse big crunch or expand
• 1:41:01
  forever coasting, slowing but still expanding. Now we know its
• 1:41:06
  accelerating dark energy dominates future is expansion, isolation, darkness. Supernova
• 1:41:14
  revealed this fate their light carrying messages across cosmic time,
• 1:41:21
  and we listen, measure, learn what the universe is telling
• 1:41:27
  us about itself, its history, its future, and our place
• 1:41:34
  within it. But let's bring this story closer to something.
• 1:41:38
  You can almost touch your body right now. This moment
• 1:41:43
  contains fragments of dozens, maybe hundreds, of different supernova. Each
• 1:41:50
  atom with heavier nucleus than helium came from a star
• 1:41:55
  that died violently. The iron in hemoglobin carrying oxygen through
• 1:42:00
  your bloodstream forged in core collapse supernova, maybe six billion
• 1:42:06
  years ago, maybe more recently. That particular iron atom has
• 1:42:12
  been recycled through multiple generations of stars, planets, cosmic dust
• 1:42:19
  before ending up in you temporarily because you'll return it
• 1:42:26
  eventually back to Earth, back to cosmic cycle. Nothing is
• 1:42:32
  permanent except the cycle itself. The calcium strengthening your bones
• 1:42:37
  right now. Different super and ova, different time, different place
• 1:42:42
  in galaxy, but same process. Silicon burning in massive stars,
• 1:42:48
  core final hours, creating calcium, then explosion, scattering it across
• 1:42:53
  light years, mixing with other material, collapsing into new stars, planets,
• 1:42:59
  four Earth, growing, life, emerging, evolving, until that calcium ended
• 1:43:06
  up in you, supporting your skeleton. As you read this,
• 1:43:11
  think about that every element playing essential role in your
• 1:43:16
  biology has history stretching back billions of years across vast distances,
• 1:43:23
  through violent deaths and gentle births. The phosphorus in your
• 1:43:30
  DNA backbone supernova origin without it, no DNA, no genetic code,
• 1:43:37
  no heredity, no evolution, no life as we know it.
• 1:43:41
  Supernova made that possible. The sulfur in proteins supernova, the
• 1:43:46
  chlorine in cells supernova. Even trace elements zinc, copper, selenium,
• 1:43:52
  tiny amounts, but crucial for enzymes, for metabolism, for life,
• 1:43:57
  all supernova products. You are literally walking, talking thinking supernova remnant.
• 1:44:05
  Not poetic exaggeration, scientific fact. Chemical analysis confirms it. We
• 1:44:11
  know where elements come from, most from supernova, some from
• 1:44:16
  other processes, but bulk of heavy elements stellar explosions. This
• 1:44:23
  means something profound about connection between us and cosmos. We're
• 1:44:29
  not separate from universe, observing it from outside. We're part
• 1:44:37
  of it, made from it, intimately connected to its history,
• 1:44:42
  its processes, its evolution. When you look at stars, you're
• 1:44:47
  looking at relatives, distant ones, but relatives nonetheless, same material,
• 1:44:53
  same origins, same cosmic story. Carl Sagan understood this deeply.
• 1:44:59
  His rays Star Stuff contemplating Stars captures it perfectly. But
• 1:45:05
  there's more to this story than just our composition. Supernova
• 1:45:10
  shaped Solar system in ways beyond just providing elements. Evidence
• 1:45:16
  suggests that supernova might have triggered solar systems formation. About
• 1:45:23
  four zero point six billion years a go, cloud of
• 1:45:28
  gas and dust floating in Milky Way, mostly stable, not collapsing,
• 1:45:34
  just drifting. Then something disturbed it compressed it shock wave,
• 1:45:39
  perhaps from nearby supernova compression triggered gravitational collapse. Cloud began contracting, spinning,
• 1:45:47
  flattening into disk at center. Sun formed in disk, Planets
• 1:45:53
  grew from dust and gas, including Earth. We have evidence
• 1:45:58
  four this super trigger found in meteorites, primitive ones formed
• 1:46:04
  early in Solar system history. They contain short lived radioactive
• 1:46:10
  isotopes like aluminum twenty six half life only seven one
• 1:46:15
  hundred thousand years. Shouldn't exist in meteorites billions of years
• 1:46:21
  old unless it was created shortly before Solar system formed,
• 1:46:28
  and only one known process creates aluminum twenty six in
• 1:46:33
  large quantities, supernova nucleosynthesis. So supernova exploded nearby, perhaps ten
• 1:46:40
  light years away, injected fresh radioactive material into cloud. Shockwave,
• 1:46:47
  compressed cloud triggered collapse, Solar system began forming. We owe
• 1:46:53
  our existence not just to material from supernova, but possibly
• 1:46:58
  to supernova trigger Solar systems birth. Without that explosion, cloud
• 1:47:05
  might never have collapsed. No Sun, no planets, no Earth,
• 1:47:09
  no US. Of course, this is hypothesis, not proven definitively,
• 1:47:15
  but evidence is strong and its beautiful idea that violent
• 1:47:20
  death of star light years away, billions of years ago
• 1:47:25
  led directly to our existence. Cause and effect across cosmic scales.
• 1:47:32
  This brings us two bigger question, how common are supernova
• 1:47:37
  in galaxy? How often do they happen? Current estimates suggest
• 1:47:42
  milky Way experiences about two to three supernova per century
• 1:47:48
  on average. Sounds rare, but consider galaxy has hundreds of
• 1:47:54
  billions of stars and has existed four billions of years.
• 1:48:01
  Total number of supernovae in milky Way's history is enormous,
• 1:48:08
  hundreds of millions, perhaps billion or more, each one enriching
• 1:48:13
  galaxy with metals, each one contributing two galactic chemical evolution.
• 1:48:20
  Over time, metallicity increases. Early universe almost pure hydrogen helium.
• 1:48:26
  First stars population three, no metals. They lived, died exploded
• 1:48:32
  enriched gas. Next generation population two low metallicity, but some
• 1:48:38
  metals present. They lived, died, exploded, further enrichment. Current generation
• 1:48:44
  population one Sun is population one, higher metallicity about two
• 1:48:50
  percent metals, enough to form rocky planets, support complex chemistry,
• 1:48:56
  enable life. This progression took billions of years, countless supernovae
• 1:49:02
  gradually building up inventory of heavy elements, and its still ongoing.
• 1:49:09
  Every super nova today adds to total galactic metallicity continues
• 1:49:14
  rising slowly over cosmic time. Eventually, star formation will cease,
• 1:49:21
  gas will be depleted, no more stars born, existing stars
• 1:49:26
  will die, last super and nova will occur, Then silence,
• 1:49:30
  no more explosions, just remnants, white dwarfs, neutron stars, black holes, cooling,
• 1:49:38
  fading forever. But that's trillions of years away. For now,
• 1:49:43
  supernova continue shaping galaxy, enriching it, driving its evolution, and
• 1:49:49
  occasionally they're visible from earth naked eye. Supernova Throughout history
• 1:49:57
  humans have witness them. Ancient China astronomers kept detailed records
• 1:50:03
  guest stars appearing suddenly, fading slowly over weeks or months.
• 1:50:10
  First recorded super nova year one eighty five a D.
• 1:50:18
  Chinese astronomers noted it visible four eight months. Modern astronomers
• 1:50:23
  identified remnant RCW eighty six in southern sky. Another famous one,
• 1:50:30
  year one zero zero six a D supernova one zero
• 1:50:34
  zero six, brightest super nova in recorded history, visible magnitude
• 1:50:41
  minus seven point five, brighter than Venus, visible during daytime
• 1:50:47
  for weeks, night sky for months. Multiple cultures recorded it China, Japan, Egypt, Europe,
• 1:50:54
  possibly Americas. Remnants still visible today, expanding shell of gas,
• 1:51:00
  beautiful structure. Then Year one zero five to four July
• 1:51:05
  fourth crab Nebula supernova. Chinese Japanese Arab astronomers recorded it
• 1:51:11
  visible in daylight four twenty three days night sky for
• 1:51:16
  six one hundred fifty three days, nearly two years. Remnant
• 1:51:23
  is crab Nebula, one of most studied objects in astronomy.
• 1:51:28
  Contains pulsar spinning neutron star rotating thirty times per second,
• 1:51:34
  emitting beams of radiation like cosmic lighthouse. Remarkable object. More
• 1:51:40
  recent super and over one six zero four Kepler's supernova.
• 1:51:45
  Johannes Kepler observed it. Last super nova visible two naked
• 1:51:50
  eye in Milky Way, over four hundred years a go.
• 1:51:55
  We're overdue for another statistically speaking, but galaxy is big.
• 1:52:00
  Most supernova happened far away, obscured by dust interstellar material.
• 1:52:07
  We don't see them invisible light, but we detect them
• 1:52:12
  other wavelengths radio, X ray, infrared, and we see plenty
• 1:52:18
  in other galaxies. Every year, hundreds discovered, thousands, Even with
• 1:52:23
  modern surveys, automated telescopes scanning sky nightly looking for transience,
• 1:52:30
  new objects appearing supernova show up regularly. Each one studied
• 1:52:36
  analyzed add into our knowledge. One supernova changed everything. Supernova
• 1:52:43
  one nine eight seven A February nineteen eighty seven, visible
• 1:52:48
  from southern Hemisphere in large Magellanic cloud, small galaxy orbiting
• 1:52:54
  Milky Way, about one sixty thousand light years away. Closest
• 1:53:00
  supernova since Kepler's and first observed with modern instruments, telescopes, detectors,
• 1:53:08
  neutrino observatories, everything it was gold mine of information before
• 1:53:14
  optical light arrived. Neutrinos detected. Three different neutrino observatories around
• 1:53:21
  world detected burst of neutrinos about three hours before optical brightening. Why.
• 1:53:29
  Because neutrinos travel nearly light speed interact weekly with matter,
• 1:53:36
  They escape stars core immediately during collapse. Light photons trapped
• 1:53:41
  inside dense stellar material takes hours, sometimes days to diffuse
• 1:53:47
  outward reach surface escape, so neutrinos arrive first early warning
• 1:53:53
  system for supernova. Super Nova one nine eight seven A.
• 1:53:59
  Twenty five neutrinos detected. Total doesn't sound like much, but
• 1:54:04
  considering how weakly neutrinos interact, detecting any is remarkable. Those
• 1:54:10
  twenty five neutrinos told us enormous amount about core collapse process, energy, released,
• 1:54:19
  neutrino flavors. Timing. Everything matched theoretical predictions, beautifully confirmed models
• 1:54:27
  of core collapse supernovae validated decades of theoretical work. It
• 1:54:33
  was triumph for astrophysics, and supernova one nine eight seven
• 1:54:39
  are kept giving over years. Decades. Astronomers watched Remnant expand
• 1:54:45
  saw rings of material ejected before explosion, lit up by
• 1:54:50
  shock wave, saw elements being created, detected radioactive decay of
• 1:54:55
  cobalt fifty six into iron fifty six, powering life light curve,
• 1:55:01
  studied pulsar or neutron star left behind, Learned about progenitor
• 1:55:07
  star blue super giant, about twenty solar masses, everything about
• 1:55:12
  supernova one nine eight seven a advanced hour, understanding enormously,
• 1:55:20
  and its still being studied today. Over thirty five years later,
• 1:55:26
  Remnant continues evolving, new features appearing as shock wave interacts
• 1:55:31
  with surrounding material. Its gift that keeps on giving. Now
• 1:55:36
  we wait for next nearby supernova in our galaxy or
• 1:55:41
  close neighbour. When it happens, will be ready. Network of telescopes,
• 1:55:48
  neutrino detectors, gravitational wave observatories, all coordinated or watching, We'll
• 1:55:54
  capture it in unprecedented detail, every wavelength, every messenger, neutrinos, photons,
• 1:56:02
  maybe even gravitational waves. If conditions rite, it will be
• 1:56:07
  spectacular scientific event of lifetime. But when will it happen
• 1:56:13
  We don't know. Could be tomorrow, could be hundred years
• 1:56:18
  from now. Stars don't announce their deaths in advance, well
• 1:56:24
  some do. Bettle juice red super giant in Orion about
• 1:56:28
  seven hundred light years away. It's nearing end of life.
• 1:56:33
  Could explode anytime, astronomically speaking, could be tomorrow, could be
• 1:56:39
  one hundred thousand years from now. We don't know precisely,
• 1:56:44
  but when it does, it will be bright visible during
• 1:56:49
  day for weeks, night sky for months, brighter than full moon.
• 1:56:55
  Perhaps it will be spectacular sight and comple deletely safe.
• 1:57:01
  Seven hundred light years too far to harm Earth. We'll
• 1:57:06
  just enjoy show, learn everything we can. Another candidate, Eta Karrinae,
• 1:57:13
  massive binary system about seven thousand light years away, one star,
• 1:57:19
  over hundred solar masses, extremely unstable, had eruption in eighteen forties.
• 1:57:26
  Great eruption ejected huge amount of material, created spectacular hermunculous
• 1:57:32
  nebula visible today. Ettakarnae could go supernova soon or might
• 1:57:38
  be thousands of years. Still, we watch it closely because
• 1:57:44
  when it explodes, it will be visible from Earth, potentially
• 1:57:49
  very bright. These are just two examples. Many massive stars
• 1:57:55
  in galaxy are candidates for future supernova. We monitor them,
• 1:58:00
  study them, try to predict, but prediction is difficult. Stars
• 1:58:05
  are complex, final stages, uncertain, so we wait and watch,
• 1:58:13
  and when next one happens, will be there, recording it,
• 1:58:19
  learning from it, adding to our understanding of these cosmic
• 1:58:25
  catastrophes that paradoxically create rather than just destroy until that
• 1:58:33
  moment arrives. Let's reflect on what supernovae mean for existence itself.
• 1:58:38
  These explosions aren't just spectacular light shows in distant corners
• 1:58:42
  of the universe. They're foundational events that made everything possible,
• 1:58:47
  including you. Every breath you take contains oxygen from supernovae,
• 1:58:54
  every heartbeat powered by iron from Stella corese, Calcium in
• 1:59:00
  your bones, carbonin your DNA, nitrogen in proteins, all forged
• 1:59:05
  in stars scattered by explosions. We are literally made of
• 1:59:10
  star stuff, as Carl Sagan said, but more specifically, we
• 1:59:15
  are made of supernova stuff. Think about that. For moment,
• 1:59:20
  billions of years ago, star somewhere in galaxy reached end
• 1:59:25
  of life. Collapsed, exploded, scattered elements into space. Those atoms
• 1:59:31
  drifted through interstellar medium, eventually condensed into new stars planets.
• 1:59:38
  One planet became Earth. Those atoms became part of oceans, mountains,
• 1:59:45
  atmosphere life. You're carrying atoms right now that were inside
• 1:59:51
  dying star experienced temperatures of billions degrees, were accelerated to
• 1:59:57
  fraction of light speed, traveled through space for eons, found
• 2:00:03
  their way here into you. Its profound connection to cosmos.
• 2:00:08
  Not metaphorical, not poetic exaggeration, its literal physical fact. Your
• 2:00:14
  body is recycled star dust supernova remnants walking around, thinking, feeling,
• 2:00:21
  wondering about their origins. But supernova do more than create elements.
• 2:00:27
  They trigger star formation. Compression from shock waves can cause
• 2:00:32
  molecular clouds to collapse form new stars. Our Sun might
• 2:00:38
  have been born this way, triggered by nearby supernova billions
• 2:00:43
  of years ago. Evidence suggests this. We find isotopes in
• 2:00:50
  meteorites that could only come from supernova present when Solar
• 2:00:57
  system formed. Short lived radioactive isotopes like aluminum twenty six
• 2:01:04
  half life just seven one hundred thousand years found in
• 2:01:08
  oldest meteorites must have been injected into solar nebula right
• 2:01:14
  before or during formation? Where could it come from? Nearby?
• 2:01:19
  Supernova explosion enriched cloud with fresh heavy elements, including radioactive ones.
• 2:01:27
  Shock wave compressed cloud triggered collapse, Sun and planets formed.
• 2:01:33
  We exist because supernova happened at right place, right time,
• 2:01:38
  nearby enough to enrich are cloud, not so close to
• 2:01:43
  destroy it. Timing had to be perfect too early isotopes
• 2:01:48
  would have decayed before incorporation, too late, Solar system already formed,
• 2:01:54
  But it happened just right Goldilocks supernova that made us possible.
• 2:02:01
  This raises fascinating question. How common is life in universe
• 2:02:06
  if it requires such specific conditions? Needs supernova to create elements,
• 2:02:12
  but not too close, not too far, Just write enrichment,
• 2:02:17
  just write timing. Given billions of stars in galaxy, trillions
• 2:02:22
  of galaxies in universe, countless supernova happening, odds seem good
• 2:02:28
  that right conditions occur many places. Maybe life isn't rare.
• 2:02:33
  Maybe it's inevitable given enough stars, enough time, enough supernovae.
• 2:02:40
  We don't know yet, but studying supernovae helps us understand
• 2:02:46
  requirements for life. Where elements come from, how they're distributed,
• 2:02:52
  what conditions needed for planets to form. Supernovae also shape
• 2:02:59
  galaxies see structure. Energy they release heats interstellar medium, creates bubbles, cavities,
• 2:03:08
  drives galactic winds. Material ejected from galaxy entirely sometimes affects
• 2:03:15
  star formation rates, galaxy evolution. In small galaxies, especially supernova
• 2:03:22
  can blow out significant fraction of gas Holt star formation
• 2:03:27
  for long periods. Galaxies too small to hold onto gas
• 2:03:32
  against supernova explosions stay small, don't form many stars in
• 2:03:38
  larger galaxies like ours. Supernova create feedback loops regulate star formation.
• 2:03:46
  Too many stars forming means more supernova, which heats gas,
• 2:03:51
  slows formation. Too few stars means fewer supernova gas calls
• 2:03:58
  formation increases its self regular system. They're also major source
• 2:04:03
  of cosmic rays, high energy particles, mostly protons that zip
• 2:04:09
  through galaxy at near light speed. Where do they come from?
• 2:04:15
  Shock Waves from supernova remnants accelerate particles to enormous energies.
• 2:04:21
  Cosmic rays have effects on Earth. They create isotopes in
• 2:04:26
  atmosphere like carbon fourteen used for dating. They cause mutations
• 2:04:33
  in DNA, contribute to evolution. They might even affect climate
• 2:04:39
  by influencing cloud formation. Hypothesis still debated but possible. So
• 2:04:45
  supernovae influence Earth even now, not just in past when
• 2:04:53
  they created elements, but ongoing through cosmic rays they produce.
• 2:05:00
  And then there's dark energy Type one A supernova. Remember
• 2:05:07
  standard candles, same brightness wherever whenever they explode. By measuring
• 2:05:13
  apparent brightness, we determine distance. By measuring redshift, we determine
• 2:05:19
  recession velocity. In nineteen nineties, two teams did this for
• 2:05:24
  distant type one A supernova. Expected to find universe expansion
• 2:05:31
  slowing down. Gravity should pull everything together, slow expansion. Instead,
• 2:05:37
  they found opposite, universe expanding faster now than past expansion accelerating.
• 2:05:44
  This was shocking, completely unexpected, one Nobel prize in two
• 2:05:50
  thy eleven. What could cause this? Some form of energy
• 2:05:55
  permeating space, pushing everything apart. They called it dark energy.
• 2:06:01
  We still don't understand what it is, but it's real,
• 2:06:06
  and it's seventy percent of universe discovered through supernova type
• 2:06:12
  one A explosions billions of light years away told us
• 2:06:17
  something fundamental about cosmos. Universe not only expanding, but acceleration.
• 2:06:22
  Fate of universe to expand forever, growing colder, darker, more empty.
• 2:06:30
  Eventually that's far future, trillions of years away. But supernova
• 2:06:37
  revealed it changed cosmology forever. Now, let's come back to present.
• 2:06:45
  What happens when we detect supernova today? Alert systems constantly
• 2:06:51
  scanning sky, automated telescopes taking images, comparing to previous images,
• 2:06:57
  looking for new points of light. When one appears, alert
• 2:07:02
  goes out within minutes. Astronomers worldwide, notified telescopes swing into action,
• 2:07:09
  ground based, space based, radio, optical, X ray, gamma ray.
• 2:07:14
  Everyone wants piece of data. Follow Up observations begin immediately.
• 2:07:20
  Spectro taken to classify type, light curves measured to track evolution.
• 2:07:27
  Neutrino detectors checked for signals if close enough. Gravitational wave
• 2:07:34
  observatories listen for signals from neutron star mergers, which also
• 2:07:41
  produce explosions. Data shared openly, rapidly. Astronomy community works together
• 2:07:48
  on transience. Time sensitive. Can't wait for publications, need data
• 2:07:54
  now to coordinate observations, understand what's happening. It's beautiful example
• 2:08:01
  of science working as should, collaboration, open sharing, collective effort
• 2:08:07
  to understand universe, and what we learn is incredible. Each
• 2:08:13
  supernova different, even same type, shows variations tells us about
• 2:08:19
  progenitor star environment, explosion mechanism. We're learning how massive stars die,
• 2:08:26
  what determines whether core collapses to neutron star or black whole,
• 2:08:32
  how much mass ejected, how elements distributed. Recent observations particularly
• 2:08:37
  interesting super nova twoenty twenty four g g I, detected
• 2:08:43
  April twenty twenty four, observed just twenty six hours after discovery.
• 2:08:50
  Very quick astronomers found shock wave breakout looked olive shaped,
• 2:08:55
  not spherical as expected. Star wasn't symmetrical when it exploded.
• 2:09:02
  Tells us something about final moments before collapse. Maybe rotation,
• 2:09:08
  maybe convection, maybe magnetic fields where still figuring out. Every
• 2:09:15
  new observation adds peace to puzzle, refines models, challenges assumptions.
• 2:09:21
  That's how science progresses, observation theory, observation theory, back and
• 2:09:28
  forth until we converge on truth. But some mysteries remain.
• 2:09:34
  How exactly does explosion mechanism work in core collapse supernova
• 2:09:40
  Models show that initial shock from bounce stalls shouldn't make
• 2:09:45
  it out, shouldn't explode star, But they do explode obviously,
• 2:09:51
  so something else must be happening. Current leading theory new
• 2:09:56
  trinos massive flux of neutrinos from proto neutron star usually
• 2:10:02
  pass through matter easily, but flux so intense, so dense,
• 2:10:07
  that's small. Fraction get absorbed by stalled shock, deposits energy,
• 2:10:13
  revives shock, drives explosion. It's called neutrino driven mechanism. Seems
• 2:10:19
  to work in simulations, matches, observations, but details still uncertain.
• 2:10:26
  Computer models incredibly complex, three dimensional, turbulent, magnetic fields, rotation,
• 2:10:34
  nuclear physics, neutrino transport, all interacting. We're getting better at simulations,
• 2:10:42
  more computing power, better physics input, but still not perfect.
• 2:10:48
  Still uncertainties. That's okay, that's science. We don't know everything yet.
• 2:10:54
  That's what makes it exciting. There's still more to discover.
• 2:11:00
  Another mystery supernova remnants, some symmetrical, some not. Some show jets,
• 2:11:07
  some don't Why. What determines structure Probably depends on progenitor star, explosion, mechanism,
• 2:11:15
  surrounding environment, but exact relationships unclear. We're studying remnants in detail.
• 2:11:23
  X ray observations show hot gas, radio observations show magnetic fields,
• 2:11:30
  cosmic rays, optical observations show filaments, knots, Infrared shows dust, molecules,
• 2:11:37
  all pieces of puzzle. Young remnants like Cassiopaya a particularly interesting,
• 2:11:45
  only about three hundred fifty years old, still expanding rapidly
• 2:11:53
  about twenty one million kilometers per hour. One of fi
• 2:12:00
  justiced shock waves ever observed shows asymmetries jets suggests explosion
• 2:12:07
  wasn't spherical, maybe star rotating. Maybe jets formed during collapse,
• 2:12:13
  punched through poles, created asymmetric remnant. We're watching it change
• 2:12:19
  in real time, comparing images from years apart, seeing expansion,
• 2:12:25
  seeing features evolve. Its living laboratory for studying supernova physics.
• 2:12:31
  Older remnants like Crab Nebula different story, about thousand years old,
• 2:12:37
  expanding slower but still active. Has pulsa in centre spinning
• 2:12:43
  thirty times per second. Powering Nebula with relativistic wind creates
• 2:12:49
  beautiful complex structure. Crab Pulser neutron star leftover from Supernova
• 2:12:55
  eleven fifty four, observed by Chinese Japanese Arab astronomers, recorded
• 2:13:02
  as guest star, visible during day for weeks nightfall months.
• 2:13:08
  Today we see remnant glowing brightly across electromagnetic spectrum. Radio
• 2:13:15
  two gamma rays powered by pulsar slowing down converting rotational
• 2:13:21
  energy into radiation particle acceleration. It will eventually fade, pulsar
• 2:13:27
  will slow stop radiating, nebula will disperse into interstellar medium,
• 2:13:34
  enriching it with heavy elements from supernova. Cycle continues. That's
• 2:13:40
  beauty of supernova. They're not end their beginning, end of star,
• 2:13:45
  but beginning of enrichment of new star, formation of planets,
• 2:13:52
  of life. Eventually, every atom in your body except hydrogen
• 2:13:57
  was made in star or supernova, your end result of
• 2:14:02
  billions of years of cosmic evolution, stellar birth, death, rebirth.
• 2:14:07
  Next time you look up at night sky, remember stars
• 2:14:12
  you see will some day die massive ones in supernova.
• 2:14:17
  They'll scatter elements into space. Those elements will form new stars,
• 2:14:23
  new planets, may be new life, and somewhere billions of
• 2:14:27
  years from now, being made from atoms created in supernova
• 2:14:32
  happening today, might look up at their sky wonder about
• 2:14:37
  their origins, just like you. That's legacy of supernova, not
• 2:14:43
  just destruction, creation, not just death, but life. They connect
• 2:14:48
  past to future stars, to planets, cosmos too, consciousness. So
• 2:14:54
  when next nearby supernova happens, whether beetlejuice or eater Carinae
• 2:14:59
  or unknown star don't just see it as distant explosion.
• 2:15:05
  See it as cosmic forge, creating elements that will someday
• 2:15:12
  become part of new world's, new beings, new stories. You're
• 2:15:18
  part of that story right now, made of super nova,
• 2:15:23
  remnants from past, living on planet, enriched by stellar deaths,
• 2:15:29
  looking out at universe that continues to evolve through saying processes.
• 2:15:35
  That's what supernova teach us. We're not separate from universe.
• 2:15:41
  We're part of it, products of it, participants in ongoing
• 2:15:46
  cosmic story of creation, destruction, transformation. Every super nova that
• 2:15:52
  happens anywhere in universe adds to that story, creates new elements,
• 2:15:59
  triggers new star formation, shapes galaxy, evolution, influences cosmic structure,
• 2:16:06
  and we're here to witness it, study it, understand it,
• 2:16:10
  appreciate it. That's privilege and responsibility to learn everything we
• 2:16:16
  can about these magnificent explosions that made us possible. The
• 2:16:22
  universe speaks through supernovae, tells us about stella evolution, nuclear physics,
• 2:16:31
  cosmic history, our own origins. All we need to do
• 2:16:38
  is listen. So here we are at the end of
• 2:16:41
  this cosmic journey through stellar death and rebirth, We've traced
• 2:16:46
  supernovae from their violent beginnings through their spectacular endings, from
• 2:16:53
  collapsing cause to expanding debris fields, from neutrino bursts to
• 2:16:58
  element creation. But what does it all mean. Let me
• 2:17:03
  tell you what strikes me most about supernova It's not
• 2:17:07
  their brightness, not their power, not even their violence. It's
• 2:17:12
  their generosity. Think about it. A star spends millions of
• 2:17:17
  years building up elements in its core layer after layer, hydrogen, helium, carbon, oxygen, silicon, iron,
• 2:17:28
  creating complexity from simplicity, building heavier elements through patient fusion. Then,
• 2:17:34
  in its final moments, it gives everything away, doesn't keep anything,
• 2:17:40
  doesn't hoard its treasures, just explodes, scatters everything it created
• 2:17:46
  across light years of space, seeds the galaxy with the
• 2:17:50
  building blocks of planets, of life of you. That's profound
• 2:17:55
  selflessness on cosmic scale. Your body can canes atoms from
• 2:18:01
  dozens of different supernovae, maybe hundreds. Each one died billions
• 2:18:07
  of years ago. Each one contributed something essential. Calcium from one,
• 2:18:13
  iron from another, oxygen from a third, all assembled in
• 2:18:17
  you temporarily because you'll give those atoms back eventually return
• 2:18:23
  them to Earth, to the cosmic cycle. Someday they'll be
• 2:18:28
  part of another star, another planet, maybe another being, looking
• 2:18:35
  up at their sky wondering about their origins. That's the
• 2:18:39
  real story of supernovae, not destruction, transformation, not endings, transitions,
• 2:18:46
  their bridges between stellar generations, connecting past to future, old
• 2:18:51
  stars to new worlds. Without them, no complexity, no chemistry
• 2:18:57
  beyond hydrogen and helium, no rocky planets, no water, no
• 2:19:02
  organic molecules, no life. The universe would be simple, boring, empty,
• 2:19:09
  but supernova changed that. They enrich the cosmos, made diversity possible,
• 2:19:15
  made us possible. Every breath you take contains oxygen from supernovae.
• 2:19:21
  Every heartbeat pumps iron created in stellar cores. Your bones
• 2:19:26
  are built from calcium forged in dying stars. Your thoughts
• 2:19:31
  flow through neurons using elements scattered by explosions billions of
• 2:19:36
  years ago. You're not just made of star stuff. You're
• 2:19:39
  made of supernova stuff. The most violent creative force in
• 2:19:44
  the universe runs through your veins. That connection to the cosmos,
• 2:19:49
  to these distant explosions. It's not metaphor. Its physics, chemistry, biology,
• 2:19:57
  all intertwined, and it continues right now somewhere in the universe.
• 2:20:03
  A star is collapsing, building towards supernova. In a few hours, days, years,
• 2:20:10
  it will explode, scatter fresh elements into space, start the
• 2:20:14
  cycle again. Maybe those elements will drift through space for
• 2:20:18
  millions of years, eventually condense into new stars, new planets.
• 2:20:24
  Maybe someday far in the future, those atoms will be
• 2:20:29
  part of living beings looking up at their sky, asking
• 2:20:34
  the same questions we ask, Where did we come from?
• 2:20:38
  What are we made of? Why are we here? The
• 2:20:41
  answers lead back to supernova. Always we're still learning. Every
• 2:20:47
  new observation teaches us something. S N twenty twenty four
• 2:20:52
  GGI with its olive shaped blast, s N nineteen eighty
• 2:20:57
  seven A with its neutrino burst, and mysterious missing remnant,
• 2:21:02
  each one unique, each one revealing new physics. Future supernova
• 2:21:07
  will teach us more when beetlejuice explodes. Whenever that happens,
• 2:21:13
  we'll watch it in unprecedented detail, every wavelength, every messenger, neutrinos, photons,
• 2:21:21
  maybe gravitational waves. It'll revolutionize our understanding. But we already
• 2:21:26
  know enough to appreciate what supernovae mean. They're not just
• 2:21:31
  astronomical events, their cosmic necessity. Without them, universe stays simple
• 2:21:39
  hydrogen and helium forever. With them, complexity emerges, Chemistry develops,
• 2:21:47
  life becomes possible. They're destructive and creative, simultaneously ending and
• 2:21:54
  beginning in same moment. That duality, that paradox. It's beautiful
• 2:22:00
  found because life works the same way. Endings enable beginnings,
• 2:22:05
  Death feeds life. Nothing lasts forever, but everything transforms, continues
• 2:22:12
  in different form. Supernova embody this truth on grandest scale.
• 2:22:17
  Star diyes, galaxy, lives, elements scatter new world's form. Consciousness
• 2:22:24
  emerges from stellar ashes, looks back at the process that
• 2:22:28
  created it, marvels at its own existence. That's where we
• 2:22:34
  are right now, products of supernova, made from their remnants,
• 2:22:41
  studying them, understanding them, appreciating them. Its circular, recursive, self referential,
• 2:22:51
  the universe examining itself through us, Supernova creating the observers
• 2:22:57
  who observe supernova. Karl Sagan said, where star stuff contemplating stars.
• 2:23:03
  He was right, but more specifically, where supernova remnants, contemplating supernova,
• 2:23:10
  the explosions that made us possible. There's poetry in that
• 2:23:15
  science and beauty intertwined. When you look up tonight at
• 2:23:19
  the stars scattered across the darkness. Remember, some of them
• 2:23:24
  will explode someday, scatter their contents across space, enrich the
• 2:23:30
  galaxy further, trigger new star formation, continue the cycle, and
• 2:23:35
  atoms from those explosions, billions of years from now might
• 2:23:41
  become part of something wonderful, something alive, something conscious, something
• 2:23:47
  asking questions about its origins, just like atoms from ancient supernova,
• 2:23:53
  long gone, long forgotten, became part of you. That's the legacy,
• 2:23:59
  the gift, the meaning of supernova not destruction, creation, not death,
• 2:24:05
  life not endings, transformations that never truly end. The universe
• 2:24:10
  recycles everything. Nothing is wasted, nothing is lost, just transformed, redistributed,
• 2:24:18
  reborn in different forms. Supernovae are the engines of this transformation,
• 2:24:24
  cosmic forges, stellar phoenixes, rising from their own ashes to
• 2:24:29
  create something new. And your proof it works, standing here, breathing, thinking, wondering,
• 2:24:39
  made entirely from the ashes of dead stars, from supernova
• 2:24:44
  remnants that drifted through space for eons before finding their
• 2:24:48
  way to Earth into you. That's not just science. That's miracle,
• 2:24:54
  cosmic miracle written in physics and chemistry, but miracle nonetheless.
• 2:25:01
  So the next time you hear about a supernova somewhere
• 2:25:05
  in some distant galaxy. Don't just think of it as explosion.
• 2:25:09
  Think of it as creation, as cosmic gardener, planting seeds
• 2:25:14
  that will grow into stars and planets and maybe life.
• 2:25:18
  Think of it as your ancestor, your maker, the source
• 2:25:22
  of everything you are, because that's exactly what it is.
• 2:25:26
  And somewhere right now, another star is preparing to give
• 2:25:31
  that gift, to scatter its treasures across the cosmos, to
• 2:25:35
  seed the future with possibility. The cycle continues, always has,
• 2:25:41
  always will until the last star burns out, the last
• 2:25:45
  super nova explodes, and the universe goes dark. But that's
• 2:25:50
  trillions of years away. For now, the fireworks continue, the
• 2:25:55
  creation continues, the transformation continues, and we're here to witness it,
• 2:26:01
  study it, understand it, be grateful for it, because without supernova,
• 2:26:07
  you wouldn't be here reading this, breathing, thinking existing. You
• 2:26:14
  owe your existence to stellar explosions, to violent deaths of stars,
• 2:26:19
  to the generosity of the cosmos giving everything away so
• 2:26:23
  something new can emerge. That's what really happens. When a
• 2:26:27
  star goes super nova. It dies, so you can live