WEBVTT 00:00:07.439 --> 00:00:10.660 Howdy Star Gazers and welcome to Star Trails. 00:00:10.939 --> 00:00:13.740 My name is Drew and I'll be your guide to the 00:00:13.740 --> 00:00:16.980 night sky for the week of October the 19th through 00:00:16.980 --> 00:00:21.179 the 25th. The calendar says late October and 00:00:21.179 --> 00:00:24.730 the heavens agree. Crisp air, long nights, and 00:00:24.730 --> 00:00:27.609 a new moon make this one of the best observing 00:00:27.609 --> 00:00:31.190 weeks of the year. And since Halloween creeps 00:00:31.190 --> 00:00:34.270 ever closer, we're continuing our eerie tour 00:00:34.270 --> 00:00:37.890 of the cosmos with a visit to a place both beautiful 00:00:37.890 --> 00:00:42.049 and haunting, the Cosmic Graveyard, where dead 00:00:42.049 --> 00:00:46.070 stars still whisper across time. Whether you're 00:00:46.070 --> 00:00:48.689 tuning in from the backyard, the balcony, or 00:00:48.689 --> 00:00:51.189 just your imagination, I'm glad you're here. 00:00:51.340 --> 00:00:55.100 So, find a cozy spot, let your eyes adjust, and 00:00:55.100 --> 00:00:57.979 let's see what the sky holds for us this week. 00:00:59.920 --> 00:01:02.840 The moon disappears this week, reaching its new 00:01:02.840 --> 00:01:07.239 phase on Tuesday, October 21st. That means a 00:01:07.239 --> 00:01:10.019 stretch of wonderfully dark skies from Sunday 00:01:10.019 --> 00:01:13.400 through Friday, perfect for galaxies, nebula, 00:01:13.780 --> 00:01:17.329 and meteor watching. And speaking of meteors, 00:01:17.469 --> 00:01:21.269 the Orionids peak Monday night into Tuesday morning. 00:01:21.790 --> 00:01:24.890 These swift streaks are the dust of Halley's 00:01:24.890 --> 00:01:27.569 Comet, burning up as Earth plows through the 00:01:27.569 --> 00:01:30.909 debris field. With no moonlight to wash them 00:01:30.909 --> 00:01:34.150 out, you could catch 10 to 20 per hour under 00:01:34.150 --> 00:01:37.750 good conditions. Face southeast after midnight, 00:01:38.030 --> 00:01:41.730 lie back, and enjoy one of autumn's finest shows. 00:01:42.930 --> 00:01:46.950 Now for the planets. Saturn glows in the southeast 00:01:46.950 --> 00:01:51.129 after dusk, nestled in Aquarius. It's still bright 00:01:51.129 --> 00:01:54.310 and steady, and its moon Titan is visible in 00:01:54.310 --> 00:01:58.069 modest telescopes. Jupiter rises around midnight 00:01:58.069 --> 00:02:01.689 in Gemini, climbing higher each morning. Watch 00:02:01.689 --> 00:02:05.129 for its shifting cloud belts and dancing moons. 00:02:05.950 --> 00:02:09.490 Mars and Mercury linger low in the western twilight, 00:02:09.889 --> 00:02:12.710 challenging but not impossible with binoculars 00:02:12.710 --> 00:02:16.710 and a flat horizon. As the constellations wheel 00:02:16.710 --> 00:02:19.969 overhead, Pegasus and the Great Square mark the 00:02:19.969 --> 00:02:23.229 heart of the autumn sky. Follow the chain of 00:02:23.229 --> 00:02:26.270 stars east to Andromeda, and you'll find the 00:02:26.270 --> 00:02:30.729 glowing oval of M31, our neighboring galaxy, 00:02:31.090 --> 00:02:35.030 easily seen in binoculars. Below that, seek out 00:02:35.030 --> 00:02:39.550 M33, the Triangulum Galaxy, a faint but graceful 00:02:39.550 --> 00:02:43.449 swirl of starlight. Farther west, Perseus rises 00:02:43.449 --> 00:02:46.889 with a glittering double cluster, while Cassiopeia's 00:02:46.889 --> 00:02:50.930 W shape rides high, tracing the Milky Way's rich 00:02:50.930 --> 00:02:55.849 star fields. Down south near Saturn, swing your 00:02:55.849 --> 00:02:59.729 scope toward M2 in Aquarius, a fine globular 00:02:59.729 --> 00:03:02.889 cluster. And if you have a nebula filter, check 00:03:02.889 --> 00:03:06.949 out the Helix Nebula, a ghostly ring of gas that 00:03:06.949 --> 00:03:10.919 lives up to its nickname, the Eye of God. Stay 00:03:10.919 --> 00:03:14.020 up past midnight and you'll see Taurus climb 00:03:14.020 --> 00:03:17.419 the eastern sky, bringing the Hyades and the 00:03:17.419 --> 00:03:27.379 Pleiades, the first messengers of winter. Before 00:03:27.379 --> 00:03:29.960 we get into the second half of the show, I wanted 00:03:29.960 --> 00:03:32.840 to respond to an excellent listener question, 00:03:33.240 --> 00:03:36.400 and it's one that's been on my mind also. The 00:03:36.400 --> 00:03:39.569 listener writes, I'm seeing the same artist's 00:03:39.569 --> 00:03:42.650 depiction of a black hole everywhere lately, 00:03:43.169 --> 00:03:46.409 notably as the logo for the AI service Grok, 00:03:46.650 --> 00:03:50.069 which appears all over Twitter or X, but also 00:03:50.069 --> 00:03:53.650 in movies like Interstellar. Is this really what 00:03:53.650 --> 00:03:57.379 a black hole looks like? Thanks for that question, 00:03:57.699 --> 00:04:00.460 and if you follow any space news, you probably 00:04:00.460 --> 00:04:03.199 know exactly what the listener is referring to. 00:04:03.740 --> 00:04:06.879 That striking, impossible -looking figure that 00:04:06.879 --> 00:04:10.400 sort of resembles a ringed planet, maybe if designed 00:04:10.400 --> 00:04:14.849 by MC Escher. It's sort of a glowing lopsided 00:04:14.849 --> 00:04:17.829 ring with a dark center, and it's been plastered 00:04:17.829 --> 00:04:21.629 across science videos, documentaries, space agency 00:04:21.629 --> 00:04:24.990 posters, and yes, the logo for the ex -owned 00:04:24.990 --> 00:04:29.470 AI service, Grok. It looks almost too perfect, 00:04:29.569 --> 00:04:32.449 like some digital artist cooked it up after a 00:04:32.449 --> 00:04:36.089 late -night sci -fi binge. In case you've never 00:04:36.089 --> 00:04:38.290 seen one of these depictions, I'll include a 00:04:38.290 --> 00:04:42.089 link to such an image in the show notes. Well, 00:04:42.089 --> 00:04:45.490 here's the twist. That image is rooted in the 00:04:45.490 --> 00:04:48.629 actual physics of how black holes warp light. 00:04:49.310 --> 00:04:52.009 What looks like a sleek bit of graphic design 00:04:52.009 --> 00:04:57.029 is possibly a very accurate visualization. Let's 00:04:57.029 --> 00:05:01.250 unpack it. At the center of that image is a dark 00:05:01.250 --> 00:05:04.269 patch. It isn't the black hole itself, because 00:05:04.269 --> 00:05:07.569 you can't actually see a black hole. Think of 00:05:07.569 --> 00:05:11.040 it as the shadow of a black hole. When light 00:05:11.040 --> 00:05:14.879 from hot gas passes near the event horizon, the 00:05:14.879 --> 00:05:18.920 black hole's gravity bends those paths. Photons 00:05:18.920 --> 00:05:22.019 that get too close are trapped forever, creating 00:05:22.019 --> 00:05:24.920 a dark silhouette slightly larger than the event 00:05:24.920 --> 00:05:27.879 horizon. That's what we're looking at when we 00:05:27.879 --> 00:05:31.420 see that central void. Surrounding it is the 00:05:31.420 --> 00:05:34.680 bright thin ring. That's made of photons that 00:05:34.680 --> 00:05:37.720 have orbited the black hole before escaping toward 00:05:37.720 --> 00:05:41.720 us. Think of light caught in a cosmic racetrack 00:05:41.720 --> 00:05:45.879 looping around at breakneck speed, then slingshotting 00:05:45.879 --> 00:05:49.240 off to hit our telescopes. This is called the 00:05:49.240 --> 00:05:53.180 photon ring, and its existence is a direct consequence 00:05:53.180 --> 00:05:57.079 of Einstein's general relativity. But the part 00:05:57.079 --> 00:05:59.699 that really gives the image its distinctive shape 00:05:59.699 --> 00:06:02.839 is the crescent, the brighter arc on one side 00:06:02.839 --> 00:06:07.060 of the ring. That asymmetry is due to a relativistic 00:06:07.060 --> 00:06:11.100 effect called Doppler boosting. Contrary to what 00:06:11.100 --> 00:06:14.220 we might think, black holes don't just suck in 00:06:14.220 --> 00:06:17.860 matter from every direction. In almost all cosmic 00:06:17.860 --> 00:06:21.259 environments, the gas around them has some spin. 00:06:22.339 --> 00:06:25.040 Thanks to the conservation of angular momentum, 00:06:25.439 --> 00:06:28.720 that gas can't just fall straight in. It forms 00:06:28.720 --> 00:06:34.050 a flat, spinning accretion disk. Over time, turbulence 00:06:34.050 --> 00:06:37.230 and magnetic forces shuffle angular momentum 00:06:37.230 --> 00:06:40.629 outward, letting material slowly spiral inward 00:06:40.629 --> 00:06:44.370 and heat up. This disk is what lights up so brightly 00:06:44.370 --> 00:06:47.310 that we can actually see the black hole's surroundings, 00:06:47.810 --> 00:06:50.569 even though the hole itself remains invisible. 00:06:51.529 --> 00:06:54.250 The gas in the accretion disk is whipping around 00:06:54.250 --> 00:06:56.990 the black hole at a significant fraction of the 00:06:56.990 --> 00:06:59.939 speed of light. On the side rotating towards 00:06:59.939 --> 00:07:03.160 us, the light is intensified. On the opposite 00:07:03.160 --> 00:07:06.779 side, it's dimmed. The result is that glowing 00:07:06.779 --> 00:07:11.600 curve you see. In 2019, the Event Horizon Telescope 00:07:11.600 --> 00:07:14.699 gave us the first real image of a black hole's 00:07:14.699 --> 00:07:19.160 shadow in the galaxy M87, and it looked a lot 00:07:19.160 --> 00:07:23.379 like these simulation images. A glowing asymmetric 00:07:23.379 --> 00:07:27.779 ring around a dark center. So far, it's our best 00:07:27.779 --> 00:07:30.959 glimpse at gravity in its purest, most extreme 00:07:30.959 --> 00:07:35.199 form. In a moment, we'll leave the living sky 00:07:35.199 --> 00:07:39.100 behind and step into a darker realm, a place 00:07:39.100 --> 00:07:42.720 where suns have burned out, galaxies devour one 00:07:42.720 --> 00:07:46.980 another, and time itself decays to silence. We're 00:07:46.980 --> 00:07:50.240 headed into the cosmic graveyard. That's coming 00:07:50.240 --> 00:08:06.779 up after the break. Stay with us. Welcome back. 00:08:07.939 --> 00:08:11.620 Tonight we walk among the tombstones of the universe. 00:08:12.500 --> 00:08:15.779 Our destination is not a place, but a condition. 00:08:16.399 --> 00:08:20.120 The cold and quiet aftermath of creation itself. 00:08:20.839 --> 00:08:29.360 This is the Cosmic Graveyard. When you look up, 00:08:29.560 --> 00:08:33.629 the stars seem eternal. But many of those pinpoints 00:08:33.629 --> 00:08:37.190 are already dead, their light still traveling 00:08:37.190 --> 00:08:40.590 towards us, tricking our eyes with the glow of 00:08:40.590 --> 00:08:44.889 long -expired suns. The universe is a cemetery 00:08:44.889 --> 00:08:48.929 of extinguished stars and broken galaxies, a 00:08:48.929 --> 00:08:52.070 realm where everything bright must one day fade. 00:08:57.089 --> 00:09:00.710 First, let's take a look at white dwarves, the 00:09:00.710 --> 00:09:05.889 embers of suns. Stars like our sun end their 00:09:05.889 --> 00:09:10.230 lives gently. They swell into red giants, shed 00:09:10.230 --> 00:09:12.830 their outer layers, and leave behind a dense 00:09:12.830 --> 00:09:16.970 core about the size of Earth. That remaining 00:09:16.970 --> 00:09:20.830 ember is a white dwarf, a glowing cinder cooling 00:09:20.830 --> 00:09:24.710 slowly for billions of years. Someday, each will 00:09:24.710 --> 00:09:27.840 fade to invisibility. becoming a black dwarf, 00:09:28.399 --> 00:09:31.039 though the universe isn't old enough for any 00:09:31.039 --> 00:09:35.740 to exist yet. They are the quiet ashes of creation. 00:09:40.500 --> 00:09:45.360 Then there are neutron stars, the undead pulsars. 00:09:46.240 --> 00:09:50.120 Massive stars die violently. Their cores collapse 00:09:50.120 --> 00:09:53.600 in a flash, crushing protons and electrons into 00:09:53.600 --> 00:09:57.750 neutrons. The resulting neutron star packs the 00:09:57.750 --> 00:10:01.389 sun's mass into a sphere just a dozen miles wide. 00:10:02.029 --> 00:10:05.309 A teaspoon of that matter outweighs a mountain. 00:10:07.070 --> 00:10:10.950 Some spin rapidly, beaming radio pulses into 00:10:10.950 --> 00:10:20.309 space. We call them pulsars, rotating corpses 00:10:20.309 --> 00:10:25.820 that tick like cosmic clocks. When first discovered 00:10:25.820 --> 00:10:30.539 they were nicknamed LGM 1 for little green men 00:10:30.539 --> 00:10:33.899 But these aren't signals from aliens. They're 00:10:33.899 --> 00:10:38.360 the heartbeats of dead stars that refuse to stop 00:10:38.360 --> 00:10:46.559 Then there are black holes Graves with no bottom 00:10:46.559 --> 00:10:50.500 for the heaviest stars gravity wins completely 00:10:50.500 --> 00:10:54.100 their cores collapse beyond recovery forming 00:10:54.100 --> 00:10:57.700 black holes, regions where not even light can 00:10:57.700 --> 00:11:01.879 escape. They devour nearby stars, twist time 00:11:01.879 --> 00:11:06.019 and shape entire galaxies. They're tombs without 00:11:06.019 --> 00:11:09.539 headstones, yet they also sculpt the cosmos. 00:11:13.899 --> 00:11:16.919 But even black holes will not endure forever. 00:11:17.620 --> 00:11:20.539 Physicist Stephen Hawking showed that black holes 00:11:20.539 --> 00:11:24.710 leak energy. tiny sparks of radiation. And that 00:11:24.710 --> 00:11:27.850 means given enough time, even these ultimate 00:11:27.850 --> 00:11:37.769 graves will evaporate into nothing. Even galaxies 00:11:37.769 --> 00:11:42.389 can die, and they cannibalize each other. Galaxies 00:11:42.389 --> 00:11:45.789 themselves expire through consumption. Big ones 00:11:45.789 --> 00:11:48.870 devour small ones, scattering stellar remains 00:11:48.870 --> 00:11:56.159 across the cosmos. Our own Milky Way is guilty. 00:11:56.419 --> 00:11:59.539 Right now, it's consuming the Sagittarius dwarf 00:11:59.539 --> 00:12:03.460 galaxy. It's stars smeared across the sky like 00:12:03.460 --> 00:12:07.960 ashes scattered by a cosmic wind. And in about 00:12:07.960 --> 00:12:11.340 four billion years, Andromeda will collide with 00:12:11.340 --> 00:12:15.320 us. Two spirals locked together, merging into 00:12:15.320 --> 00:12:19.179 a single bloated relic. Even in death, gravity 00:12:19.179 --> 00:12:26.259 hungers. The far future brings the great dimming. 00:12:26.700 --> 00:12:30.899 Eventually, star birth ceases, the last red dwarfs 00:12:30.899 --> 00:12:35.879 fade, the galaxies darken, and black holes evaporate. 00:12:43.240 --> 00:12:47.500 The cosmos cools toward absolute zero, the heat 00:12:47.500 --> 00:12:53.200 death of everything. It's a state of perfect 00:12:53.200 --> 00:12:56.259 equilibrium where no energy remains to power 00:12:56.259 --> 00:13:01.019 change, light, or life. Just the last photons 00:13:01.019 --> 00:13:14.379 drifting through infinite darkness. If the stars 00:13:14.379 --> 00:13:16.539 spoke to you this week or if a question's been 00:13:16.539 --> 00:13:20.059 on your mind, I'd love to hear it. Visit StarTrails 00:13:20.059 --> 00:13:23.700 .Show where you can contact me and explore past 00:13:23.700 --> 00:13:27.039 episodes. Be sure to follow Star Trails on Blue 00:13:27.039 --> 00:13:30.259 Sky and YouTube. Links are in the show notes. 00:13:30.919 --> 00:13:33.419 Until we meet again beneath the stars, clear 00:13:33.419 --> 00:13:34.259 skies everyone.