WEBVTT 00:00:07.139 --> 00:00:10.419 Howdy Star Gazers and welcome to Star Trails. 00:00:10.679 --> 00:00:13.400 I'm Drew and I'll be your guide to the night 00:00:13.400 --> 00:00:17.320 sky for the week of October the 12th to the 18th. 00:00:17.500 --> 00:00:20.339 This week we're moving deeper into autumn and 00:00:20.339 --> 00:00:23.960 the sky is shifting gears. Longer nights, crisp 00:00:23.960 --> 00:00:27.179 air, and the fading moon are about to make for 00:00:27.179 --> 00:00:31.039 some excellent observing conditions. Also, we 00:00:31.039 --> 00:00:33.780 continue our march toward Halloween with another 00:00:33.780 --> 00:00:37.539 eerie observation. This week we journey into 00:00:37.539 --> 00:00:40.780 the house of a thousand mirrors to examine one 00:00:40.780 --> 00:00:44.979 of my favorite topics, the weird world of gravitational 00:00:44.979 --> 00:00:48.539 lensing. Whether you're tuning in from the backyard, 00:00:48.859 --> 00:00:51.780 the balcony, or just your imagination, I'm glad 00:00:51.780 --> 00:00:55.100 you're here. So find a cozy spot, let your eyes 00:00:55.100 --> 00:00:57.859 adjust, and let's see what the sky holds for 00:00:57.859 --> 00:01:02.740 us this week. The week begins with a waning gibbous 00:01:02.740 --> 00:01:06.519 moon just past full. On Monday the moon reaches 00:01:06.519 --> 00:01:09.659 last quarter and thins into a waning crescent 00:01:09.659 --> 00:01:13.060 rising later each night. That means the second 00:01:13.060 --> 00:01:15.719 half of the week will bring darker skies in the 00:01:15.719 --> 00:01:19.260 late evening perfect for galaxies, nebula and 00:01:19.260 --> 00:01:23.120 faint star clusters. The planetary lineup is 00:01:23.120 --> 00:01:26.629 solid this week. Saturn takes the spotlight right 00:01:26.629 --> 00:01:30.010 after dusk. It's hanging in Aquarius, high enough 00:01:30.010 --> 00:01:33.709 for steady views by mid -evening. It passed opposition 00:01:33.709 --> 00:01:36.730 back in September, so it's still bright and its 00:01:36.730 --> 00:01:40.609 moon Titan is easy to spot even in a modest telescope. 00:01:41.750 --> 00:01:45.790 Neptune is over in Pisces, best seen around midnight. 00:01:46.250 --> 00:01:49.730 Look for it as a tiny bluish dot in binoculars. 00:01:50.900 --> 00:01:54.819 Uranus rises later in the evening in Aries, steadily 00:01:54.819 --> 00:01:58.760 climbing toward its November opposition. Under 00:01:58.760 --> 00:02:01.959 suburban skies, it's easy to catch with binoculars 00:02:01.959 --> 00:02:05.359 and shows a small greenish disk in a telescope. 00:02:06.980 --> 00:02:09.199 Jupiter doesn't make its entrance until the early 00:02:09.199 --> 00:02:12.159 morning hours, but when it does, it dominates 00:02:12.159 --> 00:02:15.879 the sky. It's rising earlier each night and will 00:02:15.879 --> 00:02:19.719 reach opposition in January. So this is the beginning 00:02:19.719 --> 00:02:23.159 of its best observing season. And don't miss 00:02:23.159 --> 00:02:26.879 Venus now reemerging as a brilliant morning star 00:02:26.879 --> 00:02:30.360 in the pre -dawn sky. By week's end, you'll see 00:02:30.360 --> 00:02:33.240 it low in the east with a delicate crescent moon 00:02:33.240 --> 00:02:36.780 nearby. An excellent photo opportunity if you 00:02:36.780 --> 00:02:40.919 have a clear horizon. Mars and Mercury are low 00:02:40.919 --> 00:02:43.879 and tricky this week. Mars is fading into the 00:02:43.879 --> 00:02:47.169 twilight. and Mercury will become more visible 00:02:47.169 --> 00:02:51.110 later in the month. The Orionid meteor shower, 00:02:51.270 --> 00:02:54.550 made of dust from Halley's Comet, is ramping 00:02:54.550 --> 00:02:58.150 up. The official peak is on October 21st, but 00:02:58.150 --> 00:03:01.930 during our week, early Orionids are already visible. 00:03:02.590 --> 00:03:05.210 For your best chance, head out after midnight, 00:03:05.729 --> 00:03:09.009 face east, and watch as Orion climbs higher in 00:03:09.009 --> 00:03:12.490 the sky. Late in the week, the dimming moon will 00:03:12.490 --> 00:03:16.080 make it easier to spot them. Constellations of 00:03:16.080 --> 00:03:19.219 autumn are rising. We mentioned the great square 00:03:19.219 --> 00:03:23.300 of Pegasus last week, and how to locate the Andromeda 00:03:23.300 --> 00:03:27.659 galaxy. If you revisit that same area, look for 00:03:27.659 --> 00:03:32.780 M33, the Triangulum galaxy, a faint but rewarding 00:03:32.780 --> 00:03:36.219 catch. And while you're in Pegasus, don't miss 00:03:36.219 --> 00:03:40.520 M15, a bright, compact globular cluster that 00:03:40.520 --> 00:03:43.159 looks great even under moderate light pollution. 00:03:43.550 --> 00:03:47.330 Overhead at dusk, Cygnus is still well placed, 00:03:47.650 --> 00:03:50.849 its Milky Way lanes glowing faintly in darker 00:03:50.849 --> 00:03:54.770 skies. A telescope with a nebula filter can reveal 00:03:54.770 --> 00:03:58.110 the Veil Nebula or the North America Nebula, 00:03:58.629 --> 00:04:01.409 especially during the moon -free later part of 00:04:01.409 --> 00:04:05.129 the week. Down south near Saturn, swing your 00:04:05.129 --> 00:04:09.889 scope to M2 in Aquarius, a fine globular cluster, 00:04:10.349 --> 00:04:14.169 and the Helix Nebula, a ghostly planetary nebula 00:04:14.169 --> 00:04:19.149 that really pops with an O3 or UHC filter. And 00:04:19.149 --> 00:04:22.189 if you're up late or early, you'll see Taurus 00:04:22.189 --> 00:04:26.689 rising in the east. The Hyades and Pleiades star 00:04:26.689 --> 00:04:30.029 clusters sparkle in the pre -dawn sky, signaling 00:04:30.029 --> 00:04:32.949 that winter constellations are on their way. 00:04:33.790 --> 00:04:37.029 And don't forget to check NASA's Spot the Station 00:04:37.029 --> 00:04:41.569 app for ISS flyovers. A bright pass can add a 00:04:41.569 --> 00:04:44.170 little unexpected excitement to your observing 00:04:44.170 --> 00:04:48.439 session. In a moment, we'll step into a place 00:04:48.439 --> 00:04:52.939 where light bends, time folds, and a single galaxy 00:04:52.939 --> 00:04:56.500 can appear a dozen times over. We'll explore 00:04:56.500 --> 00:04:59.959 the House of a Thousand Mirrors, where gravity 00:04:59.959 --> 00:05:03.699 itself builds a cosmic funhouse. That's coming 00:05:03.699 --> 00:05:20.779 up after the break. Stay with us. Welcome back. 00:05:22.019 --> 00:05:25.139 Imagine drifting alone through intergalactic 00:05:25.139 --> 00:05:30.180 space, no stars, no planets, no sound, just the 00:05:30.180 --> 00:05:34.860 faint cold light of distant galaxies. Then there 00:05:34.860 --> 00:05:39.279 it is, a single quasar, bright and sharp, and 00:05:39.279 --> 00:05:43.459 another, and another, and another. The same object 00:05:43.459 --> 00:05:46.839 repeated again and again, hanging in the void 00:05:46.839 --> 00:05:51.579 like reflections in a hallway of mirrors. What 00:05:51.579 --> 00:05:54.300 you're seeing isn't a trick of your eyes. It 00:05:54.300 --> 00:05:57.339 isn't a glitch in your telescope. It's the universe 00:05:57.339 --> 00:06:01.040 itself bending light into impossible shapes. 00:06:02.019 --> 00:06:05.060 Welcome to what I call the cosmic version of 00:06:05.060 --> 00:06:11.189 the house of a thousand mirrors. This strange 00:06:11.189 --> 00:06:15.410 funhouse is built by gravity, more specifically 00:06:15.410 --> 00:06:19.230 gravitational lensing, one of the most breathtaking 00:06:19.230 --> 00:06:23.069 predictions of Einstein's general theory of relativity. 00:06:24.930 --> 00:06:28.310 Einstein showed that massive objects, stars, 00:06:28.769 --> 00:06:32.930 galaxies, star clusters, don't just sit in space, 00:06:33.329 --> 00:06:37.910 they curve space -time itself. Light, always 00:06:37.910 --> 00:06:41.089 following the straightest possible path, bends 00:06:41.089 --> 00:06:44.589 along those curves like a car following a winding 00:06:44.589 --> 00:06:49.310 mountain road. Picture a glass marble placed 00:06:49.310 --> 00:06:53.310 on a stretched rubber sheet. Roll a bead of light 00:06:53.310 --> 00:06:57.430 nearby and it veers off course. Now, scale that 00:06:57.430 --> 00:07:01.180 up to a galaxy weighing trillions of suns. The 00:07:01.180 --> 00:07:04.660 result is a natural lens, an effect that can 00:07:04.660 --> 00:07:09.319 resemble a funhouse mirror. There are different 00:07:09.319 --> 00:07:13.240 kinds of gravitational lensing. Strong lensing 00:07:13.240 --> 00:07:16.639 is the funhouse variety, the one that splits 00:07:16.639 --> 00:07:19.939 a single object into multiple distinct images. 00:07:20.560 --> 00:07:24.740 These are the mirrors you can actually see. Weak 00:07:24.740 --> 00:07:28.339 lensing is subtle, like a warped reflection in 00:07:28.339 --> 00:07:31.870 an old window. Astronomers use it statistically 00:07:31.870 --> 00:07:35.389 to map the invisible skeleton of the universe. 00:07:36.910 --> 00:07:40.129 And micro -lensing happens when stars briefly 00:07:40.129 --> 00:07:43.709 magnify distant objects like flickering lanterns 00:07:43.709 --> 00:07:48.069 in the dark. But for our purposes tonight, it's 00:07:48.069 --> 00:07:51.350 strong lensing that turns the universe into something 00:07:51.350 --> 00:07:54.939 eerie. A place where a single object can appear 00:07:54.939 --> 00:07:58.240 dozens of times, scattered across the sky like 00:07:58.240 --> 00:08:02.019 a shattered reflection. One of the most famous 00:08:02.019 --> 00:08:06.519 examples is the Einstein Cross, a quasar billions 00:08:06.519 --> 00:08:09.720 of light years away, whose light is split into 00:08:09.720 --> 00:08:13.180 four identical points arranged neatly around 00:08:13.180 --> 00:08:17.379 a foreground galaxy. It looks like a cosmic emblem. 00:08:19.120 --> 00:08:24.759 Then there's Abell 1689, a massive galaxy cluster 00:08:24.759 --> 00:08:27.660 that bends light so dramatically it produces 00:08:27.660 --> 00:08:31.480 arcs, rings, and multiple mirror images of galaxies 00:08:31.480 --> 00:08:35.419 hiding far behind it. If you've ever seen those 00:08:35.419 --> 00:08:39.259 long ghostly arcs and Hubble images, that's Abell 00:08:39.259 --> 00:08:45.500 1689 at work. Perhaps the most astonishing example 00:08:45.500 --> 00:08:51.799 is Max J1149. In 2014, astronomers witnessed 00:08:51.799 --> 00:08:55.940 the explosion of a distant supernova named Refsdal. 00:08:56.659 --> 00:09:00.279 Then, a year later, they saw it again. The light 00:09:00.279 --> 00:09:02.879 had traveled through different routes in the 00:09:02.879 --> 00:09:07.080 warped space -time of a galaxy cluster. One path 00:09:07.080 --> 00:09:10.500 was shorter, one was longer. It was the same 00:09:10.500 --> 00:09:15.860 explosion appearing twice. This is time itself, 00:09:16.419 --> 00:09:26.379 folded by gravity. In an actual hall of mirrors, 00:09:26.860 --> 00:09:29.720 light bounces from surface to surface, arriving 00:09:29.720 --> 00:09:33.419 at your eyes at different moments. Gravitational 00:09:33.419 --> 00:09:36.759 lensing works in a similar way, but the mirrors 00:09:36.759 --> 00:09:39.940 aren't made of glass. They're made of space -time. 00:09:40.600 --> 00:09:43.539 Light from a distant quasar might arrive at Earth 00:09:43.539 --> 00:09:46.820 by multiple routes, some taking longer than others. 00:09:47.299 --> 00:09:50.220 It's kind of like watching the same film twice, 00:09:50.399 --> 00:09:54.740 but from different theater seats. This cosmic 00:09:54.740 --> 00:09:58.500 rerun is eerie, but it's also incredibly useful 00:09:58.500 --> 00:10:01.960 to astronomers. By carefully measuring the time 00:10:01.960 --> 00:10:04.980 delays between these mirror images, astronomers 00:10:04.980 --> 00:10:08.379 can calculate the expansion rate of the universe. 00:10:08.879 --> 00:10:11.960 That's the Hubble constant. And interestingly, 00:10:12.440 --> 00:10:15.139 these lensing -based measurements don't quite 00:10:15.139 --> 00:10:18.899 match other methods, hinting at something strange 00:10:18.899 --> 00:10:24.799 about our cosmos. Gravitational lensing also 00:10:24.799 --> 00:10:28.059 has another use. It reveals the distribution 00:10:28.059 --> 00:10:32.039 of dark matter, the invisible mass that shapes 00:10:32.039 --> 00:10:36.379 the universe. It helps us discover galaxies too 00:10:36.379 --> 00:10:40.179 distant and faint to detect otherwise. The lens 00:10:40.179 --> 00:10:43.440 acts like a magnifying glass, boosting their 00:10:43.440 --> 00:10:47.799 light. The James Webb Space Telescope is already 00:10:47.799 --> 00:10:50.559 peering through these natural telescopes to find 00:10:50.559 --> 00:10:53.639 some of the earliest galaxies after the Big Bang. 00:10:54.759 --> 00:10:58.320 For backyard astronomers, strong lensing is challenging 00:10:58.320 --> 00:11:01.820 to spot directly, but not impossible. With a 00:11:01.820 --> 00:11:04.600 large enough telescope under dark skies, the 00:11:04.600 --> 00:11:09.019 arcs of able clusters can be teased out. More 00:11:09.019 --> 00:11:11.960 accessible, though, are the iconic images captured 00:11:11.960 --> 00:11:15.980 by Hubble and the James Webb. The Einstein cross, 00:11:16.259 --> 00:11:19.240 the frontier fields, the incredible deep field 00:11:19.240 --> 00:11:24.399 mosaics are all freely available online. The 00:11:24.399 --> 00:11:27.159 next time you look at one, take a moment to ponder. 00:11:27.460 --> 00:11:31.480 Every arc, every ghostly streak is the distorted 00:11:31.480 --> 00:11:35.200 light of a galaxy billions of years old, seen 00:11:35.200 --> 00:11:38.840 through another galaxy's gravity. You're looking 00:11:38.840 --> 00:11:43.139 into a cosmic mirror maze built by mass itself. 00:11:44.009 --> 00:11:48.370 These lenses in space replay the past and reveal 00:11:48.370 --> 00:11:56.330 the secrets hidden at the edge of time. If the 00:11:56.330 --> 00:11:58.750 stars spoke to you this week or if a question's 00:11:58.750 --> 00:12:01.529 been on your mind, I'd love to hear it. Visit 00:12:01.529 --> 00:12:05.669 our website StarTrails .Show where you can contact 00:12:05.669 --> 00:12:09.429 me and explore past episodes. Be sure to follow 00:12:09.429 --> 00:12:13.059 us on Blue Sky and YouTube. Links are in the 00:12:13.059 --> 00:12:16.100 show notes. Until we meet again beneath the stars, 00:12:16.580 --> 00:12:17.679 clear skies everyone.