Latest / Star Trails: From Backyard Astronomy to Cosmic Wonder / Echoes from the Cosmic Graveyard

Transcript

Echoes from the Cosmic Graveyard · Star Trails: From Backyard Astronomy to Cosmic Wonder

• 0:07
  Howdy Star Gazers and welcome to Star Trails.
• 0:10
  My name is Drew and I'll be your guide to the
• 0:13
  night sky for the week of October the 19th through
• 0:16
  the 25th. The calendar says late October and
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  the heavens agree. Crisp air, long nights, and
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  a new moon make this one of the best observing
• 0:27
  weeks of the year. And since Halloween creeps
• 0:31
  ever closer, we're continuing our eerie tour
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  of the cosmos with a visit to a place both beautiful
• 0:37
  and haunting, the Cosmic Graveyard, where dead
• 0:42
  stars still whisper across time. Whether you're
• 0:46
  tuning in from the backyard, the balcony, or
• 0:48
  just your imagination, I'm glad you're here.
• 0:51
  So, find a cozy spot, let your eyes adjust, and
• 0:55
  let's see what the sky holds for us this week.
• 0:59
  The moon disappears this week, reaching its new
• 1:02
  phase on Tuesday, October 21st. That means a
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  stretch of wonderfully dark skies from Sunday
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  through Friday, perfect for galaxies, nebula,
• 1:13
  and meteor watching. And speaking of meteors,
• 1:17
  the Orionids peak Monday night into Tuesday morning.
• 1:21
  These swift streaks are the dust of Halley's
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  Comet, burning up as Earth plows through the
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  debris field. With no moonlight to wash them
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  out, you could catch 10 to 20 per hour under
• 1:34
  good conditions. Face southeast after midnight,
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  lie back, and enjoy one of autumn's finest shows.
• 1:42
  Now for the planets. Saturn glows in the southeast
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  after dusk, nestled in Aquarius. It's still bright
• 1:51
  and steady, and its moon Titan is visible in
• 1:54
  modest telescopes. Jupiter rises around midnight
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  in Gemini, climbing higher each morning. Watch
• 2:01
  for its shifting cloud belts and dancing moons.
• 2:05
  Mars and Mercury linger low in the western twilight,
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  challenging but not impossible with binoculars
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  and a flat horizon. As the constellations wheel
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  overhead, Pegasus and the Great Square mark the
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  heart of the autumn sky. Follow the chain of
• 2:23
  stars east to Andromeda, and you'll find the
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  glowing oval of M31, our neighboring galaxy,
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  easily seen in binoculars. Below that, seek out
• 2:35
  M33, the Triangulum Galaxy, a faint but graceful
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  swirl of starlight. Farther west, Perseus rises
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  with a glittering double cluster, while Cassiopeia's
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  W shape rides high, tracing the Milky Way's rich
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  star fields. Down south near Saturn, swing your
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  scope toward M2 in Aquarius, a fine globular
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  cluster. And if you have a nebula filter, check
• 3:02
  out the Helix Nebula, a ghostly ring of gas that
• 3:06
  lives up to its nickname, the Eye of God. Stay
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  up past midnight and you'll see Taurus climb
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  the eastern sky, bringing the Hyades and the
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  Pleiades, the first messengers of winter. Before
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  we get into the second half of the show, I wanted
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  to respond to an excellent listener question,
• 3:33
  and it's one that's been on my mind also. The
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  listener writes, I'm seeing the same artist's
• 3:39
  depiction of a black hole everywhere lately,
• 3:43
  notably as the logo for the AI service Grok,
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  which appears all over Twitter or X, but also
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  in movies like Interstellar. Is this really what
• 3:53
  a black hole looks like? Thanks for that question,
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  and if you follow any space news, you probably
• 4:00
  know exactly what the listener is referring to.
• 4:03
  That striking, impossible -looking figure that
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  sort of resembles a ringed planet, maybe if designed
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  by MC Escher. It's sort of a glowing lopsided
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  ring with a dark center, and it's been plastered
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  across science videos, documentaries, space agency
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  posters, and yes, the logo for the ex -owned
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  AI service, Grok. It looks almost too perfect,
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  like some digital artist cooked it up after a
• 4:32
  late -night sci -fi binge. In case you've never
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  seen one of these depictions, I'll include a
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  link to such an image in the show notes. Well,
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  here's the twist. That image is rooted in the
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  actual physics of how black holes warp light.
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  What looks like a sleek bit of graphic design
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  is possibly a very accurate visualization. Let's
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  unpack it. At the center of that image is a dark
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  patch. It isn't the black hole itself, because
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  you can't actually see a black hole. Think of
• 5:07
  it as the shadow of a black hole. When light
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  from hot gas passes near the event horizon, the
• 5:14
  black hole's gravity bends those paths. Photons
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  that get too close are trapped forever, creating
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  a dark silhouette slightly larger than the event
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  horizon. That's what we're looking at when we
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  see that central void. Surrounding it is the
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  bright thin ring. That's made of photons that
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  have orbited the black hole before escaping toward
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  us. Think of light caught in a cosmic racetrack
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  looping around at breakneck speed, then slingshotting
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  off to hit our telescopes. This is called the
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  photon ring, and its existence is a direct consequence
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  of Einstein's general relativity. But the part
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  that really gives the image its distinctive shape
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  is the crescent, the brighter arc on one side
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  of the ring. That asymmetry is due to a relativistic
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  effect called Doppler boosting. Contrary to what
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  we might think, black holes don't just suck in
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  matter from every direction. In almost all cosmic
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  environments, the gas around them has some spin.
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  Thanks to the conservation of angular momentum,
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  that gas can't just fall straight in. It forms
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  a flat, spinning accretion disk. Over time, turbulence
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  and magnetic forces shuffle angular momentum
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  outward, letting material slowly spiral inward
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  and heat up. This disk is what lights up so brightly
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  that we can actually see the black hole's surroundings,
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  even though the hole itself remains invisible.
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  The gas in the accretion disk is whipping around
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  the black hole at a significant fraction of the
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  speed of light. On the side rotating towards
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  us, the light is intensified. On the opposite
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  side, it's dimmed. The result is that glowing
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  curve you see. In 2019, the Event Horizon Telescope
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  gave us the first real image of a black hole's
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  shadow in the galaxy M87, and it looked a lot
• 7:19
  like these simulation images. A glowing asymmetric
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  ring around a dark center. So far, it's our best
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  glimpse at gravity in its purest, most extreme
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  form. In a moment, we'll leave the living sky
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  behind and step into a darker realm, a place
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  where suns have burned out, galaxies devour one
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  another, and time itself decays to silence. We're
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  headed into the cosmic graveyard. That's coming
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  up after the break. Stay with us. Welcome back.
• 8:07
  Tonight we walk among the tombstones of the universe.
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  Our destination is not a place, but a condition.
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  The cold and quiet aftermath of creation itself.
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  This is the Cosmic Graveyard. When you look up,
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  the stars seem eternal. But many of those pinpoints
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  are already dead, their light still traveling
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  towards us, tricking our eyes with the glow of
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  long -expired suns. The universe is a cemetery
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  of extinguished stars and broken galaxies, a
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  realm where everything bright must one day fade.
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  First, let's take a look at white dwarves, the
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  embers of suns. Stars like our sun end their
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  lives gently. They swell into red giants, shed
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  their outer layers, and leave behind a dense
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  core about the size of Earth. That remaining
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  ember is a white dwarf, a glowing cinder cooling
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  slowly for billions of years. Someday, each will
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  fade to invisibility. becoming a black dwarf,
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  though the universe isn't old enough for any
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  to exist yet. They are the quiet ashes of creation.
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  Then there are neutron stars, the undead pulsars.
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  Massive stars die violently. Their cores collapse
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  in a flash, crushing protons and electrons into
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  neutrons. The resulting neutron star packs the
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  sun's mass into a sphere just a dozen miles wide.
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  A teaspoon of that matter outweighs a mountain.
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  Some spin rapidly, beaming radio pulses into
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  space. We call them pulsars, rotating corpses
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  that tick like cosmic clocks. When first discovered
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  they were nicknamed LGM 1 for little green men
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  But these aren't signals from aliens. They're
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  the heartbeats of dead stars that refuse to stop
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  Then there are black holes Graves with no bottom
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  for the heaviest stars gravity wins completely
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  their cores collapse beyond recovery forming
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  black holes, regions where not even light can
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  escape. They devour nearby stars, twist time
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  and shape entire galaxies. They're tombs without
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  headstones, yet they also sculpt the cosmos.
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  But even black holes will not endure forever.
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  Physicist Stephen Hawking showed that black holes
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  leak energy. tiny sparks of radiation. And that
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  means given enough time, even these ultimate
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  graves will evaporate into nothing. Even galaxies
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  can die, and they cannibalize each other. Galaxies
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  themselves expire through consumption. Big ones
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  devour small ones, scattering stellar remains
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  across the cosmos. Our own Milky Way is guilty.
• 11:56
  Right now, it's consuming the Sagittarius dwarf
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  galaxy. It's stars smeared across the sky like
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  ashes scattered by a cosmic wind. And in about
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  four billion years, Andromeda will collide with
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  us. Two spirals locked together, merging into
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  a single bloated relic. Even in death, gravity
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  hungers. The far future brings the great dimming.
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  Eventually, star birth ceases, the last red dwarfs
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  fade, the galaxies darken, and black holes evaporate.
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  The cosmos cools toward absolute zero, the heat
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  death of everything. It's a state of perfect
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  equilibrium where no energy remains to power
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  change, light, or life. Just the last photons
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  drifting through infinite darkness. If the stars
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  spoke to you this week or if a question's been
• 13:16
  on your mind, I'd love to hear it. Visit StarTrails
• 13:20
  .Show where you can contact me and explore past
• 13:23
  episodes. Be sure to follow Star Trails on Blue
• 13:27
  Sky and YouTube. Links are in the show notes.
• 13:30
  Until we meet again beneath the stars, clear
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  skies everyone.