WEBVTT 00:00:06.849 --> 00:00:09.730 Howdy Star Gazers and welcome to this episode 00:00:09.730 --> 00:00:13.150 of Star Trails. My name is Drew, and I'll be 00:00:13.150 --> 00:00:15.869 your guide to the night sky for the week of March 00:00:15.869 --> 00:00:19.989 the 8th through the 14th. This week we continue 00:00:19.989 --> 00:00:23.370 our month -long exploration of our solar system. 00:00:23.559 --> 00:00:27.100 by leaving the warm terrarium of the inner planets 00:00:27.100 --> 00:00:31.059 for the deep freezer of the outer planets. In 00:00:31.059 --> 00:00:34.600 these far reaches, our sun is no longer a dominating 00:00:34.600 --> 00:00:38.200 presence, but a bright star among many, and the 00:00:38.200 --> 00:00:41.200 worlds we find here are as strange as they are 00:00:41.200 --> 00:00:44.659 lonely. Later in the show, I'll report on my 00:00:44.659 --> 00:00:48.060 efforts to observe a recent SpaceX rocket launch. 00:00:48.520 --> 00:00:51.119 We'll press forth into the next two chapters 00:00:51.119 --> 00:00:54.259 of Night Watch, And we'll look at what you can 00:00:54.259 --> 00:00:57.719 expect to see in the night sky this week. Whether 00:00:57.719 --> 00:01:00.340 you're tuning in from the backyard or the balcony, 00:01:00.619 --> 00:01:03.320 I'm glad you're here. So grab a comfortable spot 00:01:03.320 --> 00:01:13.840 under the night sky and let's get started. Tonight 00:01:13.840 --> 00:01:16.760 we pick up where we left off in the last episode. 00:01:17.040 --> 00:01:20.500 The rusty deserts of Mars are fading in the rear 00:01:20.500 --> 00:01:23.760 -view mirror of our spaceship, and the sun begins 00:01:23.760 --> 00:01:27.040 to shrink ever so slightly into something less 00:01:27.040 --> 00:01:30.799 oppressive and more distant. Ahead of us lies 00:01:30.799 --> 00:01:34.980 the asteroid belt, not the chaotic pinball machine 00:01:34.980 --> 00:01:38.560 of science fiction, but a wide, mostly empty 00:01:38.560 --> 00:01:42.420 region stretching between Mars and Jupiter. If 00:01:42.420 --> 00:01:45.480 you could stand on Ceres, the largest object 00:01:45.480 --> 00:01:48.879 there, and it's now classified as a dwarf planet, 00:01:49.379 --> 00:01:52.260 you'd see a lonely landscape of ice and rock 00:01:52.260 --> 00:01:56.180 under a dimmer sun. The belt contains millions 00:01:56.180 --> 00:01:59.980 of objects, yes, but they're separated by vast 00:01:59.980 --> 00:02:04.319 distances. Once we clear that frontier, the solar 00:02:04.319 --> 00:02:07.670 system changes character. The outer planets are 00:02:07.670 --> 00:02:10.669 not simply bigger versions of the inner ones. 00:02:10.969 --> 00:02:15.250 They're a different category of existence. Jupiter 00:02:15.250 --> 00:02:18.409 announces itself long before you arrive. It's 00:02:18.409 --> 00:02:21.330 more massive than all the other planets combined. 00:02:21.909 --> 00:02:25.030 A gravitational monarch presiding over the outer 00:02:25.030 --> 00:02:29.250 solar system. It resides around 5 AU from the 00:02:29.250 --> 00:02:35.030 sun, or about 465 million miles. Its diameter 00:02:35.030 --> 00:02:39.030 could fit more than 11 Earths across. Its volume 00:02:39.030 --> 00:02:42.530 could swallow more than 1 ,300 Earths whole. 00:02:43.030 --> 00:02:46.490 And yet it's made mostly of hydrogen and helium. 00:02:46.969 --> 00:02:50.870 The same stuff as our Sun. Just not quite massive 00:02:50.870 --> 00:02:54.770 enough to ignite nuclear fusion. Sometimes people 00:02:54.770 --> 00:02:58.370 call it a failed star, but that's poetic shorthand. 00:02:58.789 --> 00:03:01.770 In reality, it would need about 80 times more 00:03:01.770 --> 00:03:05.909 mass to shine. Jupiter's atmosphere is a masterpiece 00:03:05.909 --> 00:03:10.250 of fluid dynamics. Cream and cinnamon -hued bands 00:03:10.250 --> 00:03:13.610 wrap around the globe, driven by jet streams 00:03:13.610 --> 00:03:16.770 moving hundreds of miles per hour. The Great 00:03:16.770 --> 00:03:20.250 Red Spot, a storm larger than Earth, has been 00:03:20.250 --> 00:03:24.330 raging for at least 350 years. It seems to be 00:03:24.330 --> 00:03:27.050 shrinking, but it's still a planetary -scale 00:03:27.050 --> 00:03:31.800 hurricane that refuses to die. Jupiter also radiates 00:03:31.800 --> 00:03:35.439 more heat than it receives from the Sun. Deep 00:03:35.439 --> 00:03:38.900 inside, gravitational compression slowly releases 00:03:38.900 --> 00:03:42.199 energy, as if the planet is still settling into 00:03:42.199 --> 00:03:45.879 itself. And then there are the moons. Four of 00:03:45.879 --> 00:03:50.099 them were spotted in 1610 by Galileo Galilei, 00:03:50.520 --> 00:03:55.539 Io, Europa, Ganymede, and Callisto. Tiny moving 00:03:55.539 --> 00:03:58.979 points of light that quietly proved not everything 00:03:58.979 --> 00:04:02.819 orbits Earth. Not surprisingly, we refer to these 00:04:02.819 --> 00:04:06.219 as the Galilean moons, and even a small scope 00:04:06.219 --> 00:04:10.080 will reveal them here on Earth. Io is the most 00:04:10.080 --> 00:04:13.219 volcanically active world in the solar system. 00:04:13.900 --> 00:04:17.399 Europa likely hides a global ocean beneath its 00:04:17.399 --> 00:04:21.000 icy shell, twice as much water as all of Earth's 00:04:21.000 --> 00:04:24.689 oceans combined. Ganymede is the largest moon 00:04:24.689 --> 00:04:27.290 in the solar system and has its own magnetic 00:04:27.290 --> 00:04:31.870 field. We've explored Jupiter extensively. Pioneer 00:04:31.870 --> 00:04:37.069 10 and 11 first passed by in the 1970s. Voyager 00:04:37.069 --> 00:04:41.029 1 and Voyager 2 gave us the iconic images that 00:04:41.029 --> 00:04:44.029 have defined our view of Jupiter for four decades. 00:04:44.480 --> 00:04:47.699 Galileo orbited the planet for eight years in 00:04:47.699 --> 00:04:52.680 the 1990s and early 2000s, and today Juno continues 00:04:52.680 --> 00:04:56.360 to dive over the poles, mapping gravity, magnetic 00:04:56.360 --> 00:04:59.500 fields, and peering deep beneath the clouds. 00:05:01.360 --> 00:05:05.019 Now let's drift outward another 400 million miles 00:05:05.019 --> 00:05:08.959 to the ringed planet. Saturn feels like Jupiter's 00:05:08.959 --> 00:05:12.800 more refined sibling. It's less massive, but 00:05:12.800 --> 00:05:16.560 visually unforgettable. Its rings stretch hundreds 00:05:16.560 --> 00:05:19.980 of thousands of miles wide, yet in places they're 00:05:19.980 --> 00:05:23.459 only tens of meters thick. Thinner than a football 00:05:23.459 --> 00:05:27.000 field is long. They're made of countless particles 00:05:27.000 --> 00:05:30.220 of ice and rock, each one following Kepler's 00:05:30.220 --> 00:05:34.740 laws with quiet obedience. Saturn's density is 00:05:34.740 --> 00:05:38.220 so low that, in theory, it would float in water, 00:05:38.519 --> 00:05:40.980 if you had an ocean large enough to hold a planet. 00:05:41.389 --> 00:05:44.990 Saturn deserves more than it has rings. That's 00:05:44.990 --> 00:05:48.290 like introducing Jimi Hendrix by saying he dabbled 00:05:48.290 --> 00:05:53.310 in guitar. So let's widen the lens. First, Saturn 00:05:53.310 --> 00:05:56.649 is not just a smaller Jupiter. It's structurally 00:05:56.649 --> 00:06:00.110 different in subtle but important ways. While 00:06:00.110 --> 00:06:03.329 both are gas giants, comprised mostly of hydrogen 00:06:03.329 --> 00:06:07.009 and helium, Saturn's core is proportionally larger 00:06:07.009 --> 00:06:10.860 relative to its total mass. That may tell us 00:06:10.860 --> 00:06:13.399 something about how and where it formed in the 00:06:13.399 --> 00:06:17.319 early solar system. Planet formation models suggest 00:06:17.319 --> 00:06:20.139 Saturn may have grown more slowly than Jupiter, 00:06:20.779 --> 00:06:23.639 accreting gas after Jupiter had already become 00:06:23.639 --> 00:06:27.620 the dominant gravitational bully. Now let's talk 00:06:27.620 --> 00:06:30.819 about those rings in more depth because they're 00:06:30.819 --> 00:06:34.540 not permanent. The rings are likely young on 00:06:34.540 --> 00:06:38.100 cosmic timescales. Current models suggest they 00:06:38.100 --> 00:06:40.819 may be only a hundred to four hundred million 00:06:40.819 --> 00:06:43.879 years old, possibly the remains of a shattered 00:06:43.879 --> 00:06:47.560 moon torn apart by tidal forces after wandering 00:06:47.560 --> 00:06:51.560 too close. When dinosaurs walked Earth, Saturn 00:06:51.560 --> 00:06:54.480 may have looked different in the sky. The rings 00:06:54.480 --> 00:06:58.180 are organized into major divisions, A, B, and 00:06:58.180 --> 00:07:01.600 C rings, with the prominent Cassini division 00:07:01.600 --> 00:07:05.990 separating A and B. That gap isn't empty. It's 00:07:05.990 --> 00:07:09.470 sculpted by gravitational resonances with Saturn's 00:07:09.470 --> 00:07:12.970 moons. In other words, the moons are choreographing 00:07:12.970 --> 00:07:17.230 the rings. Tiny shepherd moons like Prometheus 00:07:17.230 --> 00:07:21.529 and Pandora actively confine ring material, preventing 00:07:21.529 --> 00:07:25.569 it from dispersing. Even so, the rings are slowly 00:07:25.569 --> 00:07:28.569 dissolving. At current rates, they may vanish 00:07:28.569 --> 00:07:32.519 in a hundred million years or so. Saturn's North 00:07:32.519 --> 00:07:36.540 Pole hosts a bizarre persistent hexagonal storm 00:07:36.540 --> 00:07:39.839 system. It's not a trick of the eye, it's a stable 00:07:39.839 --> 00:07:43.040 wave pattern in the atmosphere, larger than Earth. 00:07:44.120 --> 00:07:46.959 Saturn currently holds the record for the most 00:07:46.959 --> 00:07:50.819 known moons, well over a hundred confirmed objects, 00:07:50.959 --> 00:07:55.459 though many are tiny captured rocks. Titan and 00:07:55.459 --> 00:07:59.199 Enceladus get the spotlight, but Iapetus is a 00:07:59.199 --> 00:08:02.779 wonder too. One hemisphere bright as snow, the 00:08:02.779 --> 00:08:07.100 other dark as coal. The yin -yang moon. The real 00:08:07.100 --> 00:08:10.600 golden age of Saturn exploration came with Cassini 00:08:10.600 --> 00:08:14.560 -Huygens. For 13 years, Cassini orbited Saturn, 00:08:15.139 --> 00:08:17.920 transforming it from a distant ringed icon into 00:08:17.920 --> 00:08:22.139 a richly detailed world. It watched seasons change. 00:08:22.420 --> 00:08:25.639 It flew through the rings. It revealed Enceladus 00:08:25.639 --> 00:08:28.519 spraying plumes of water vapor from its south 00:08:28.519 --> 00:08:32.580 pole. evidence of a subsurface ocean. It delivered 00:08:32.580 --> 00:08:35.980 the Huygens probe to Titan, where it parachuted 00:08:35.980 --> 00:08:39.299 down through a thick orange atmosphere and landed 00:08:39.299 --> 00:08:43.639 on a surface shaped by methane rain. Titan has 00:08:43.639 --> 00:08:47.700 lakes and rivers, weather, dunes, a hydrological 00:08:47.700 --> 00:08:51.139 cycle built not on water but on hydrocarbons. 00:08:51.789 --> 00:08:56.129 When Cassini ended its mission in 2017, it deliberately 00:08:56.129 --> 00:09:00.049 plunged into Saturn's atmosphere to avoid contaminating 00:09:00.049 --> 00:09:04.070 potentially habitable moons. A spacecraft choosing 00:09:04.070 --> 00:09:07.769 its own fiery end to protect alien oceans is 00:09:07.769 --> 00:09:12.529 poetic engineering. And now we reach the ice 00:09:12.529 --> 00:09:17.039 giants, Uranus and Neptune. It's wild to think 00:09:17.039 --> 00:09:19.360 that through most of my childhood, we didn't 00:09:19.360 --> 00:09:22.820 have any detailed images of either of these worlds. 00:09:23.539 --> 00:09:26.019 All the books I grew up reading just featured 00:09:26.019 --> 00:09:29.759 artist's renditions, and both planets today still 00:09:29.759 --> 00:09:33.840 remain some of the least imaged. Of the two, 00:09:34.220 --> 00:09:37.919 Uranus is the real oddball. It rotates on its 00:09:37.919 --> 00:09:41.899 side, tilted 98 degrees. It essentially rolls 00:09:41.899 --> 00:09:45.879 around the sun. Its seasons last about 20 years 00:09:45.879 --> 00:09:49.919 apiece. For decades at a time, one pole faces 00:09:49.919 --> 00:09:52.879 the sun in continuous daylight, while the other 00:09:52.879 --> 00:09:57.279 endures unbroken darkness. Its pale blue color 00:09:57.279 --> 00:10:00.740 comes from methane in its atmosphere, which absorbs 00:10:00.740 --> 00:10:04.700 red light and reflects blue. Beneath the atmosphere 00:10:04.700 --> 00:10:08.659 lies a mantle of super pressurized water, ammonia, 00:10:09.000 --> 00:10:12.840 and methane ice. Some models suggest that under 00:10:12.840 --> 00:10:16.139 those immense pressures, carbon could crystallize 00:10:16.139 --> 00:10:18.899 into diamonds that rain downward through the 00:10:18.899 --> 00:10:22.320 interior. That remains a working hypothesis, 00:10:22.460 --> 00:10:25.159 but it's consistent with high pressure physics 00:10:25.159 --> 00:10:29.559 experiments. Like Saturn, Uranus has a ring system, 00:10:29.820 --> 00:10:32.320 although they are very different in almost every 00:10:32.320 --> 00:10:36.799 way. They were discovered in 1977 during a stellar 00:10:36.799 --> 00:10:40.399 occultation experiment. Astronomers were watching 00:10:40.399 --> 00:10:43.679 Uranus pass in front of a distant star. Instead 00:10:43.679 --> 00:10:46.360 of the star dimming once as the planet moved 00:10:46.360 --> 00:10:49.580 across it, it flickered multiple times before 00:10:49.580 --> 00:10:53.039 and after the main event. That meant something 00:10:53.039 --> 00:10:56.139 thin and structured was blocking the starlight. 00:10:56.779 --> 00:11:00.519 That something turned out to be rings. Uranus' 00:11:00.720 --> 00:11:04.559 rings are narrow, dark, and composed mostly of 00:11:04.559 --> 00:11:07.919 relatively large particles mixed with radiation 00:11:07.919 --> 00:11:10.799 -processed material that makes them charcoal 00:11:10.799 --> 00:11:14.539 -colored. They don't shine so much as they lurk. 00:11:15.419 --> 00:11:19.139 There are currently 13 known rings, named mostly 00:11:19.139 --> 00:11:22.879 with Greek letters, alpha, beta, gamma, and so 00:11:22.879 --> 00:11:25.860 on, along with a few more recently discovered 00:11:25.860 --> 00:11:30.019 faint outer rings. Like Saturn's, Uranus's rings 00:11:30.019 --> 00:11:32.779 are shaped and maintained by shepherd moons. 00:11:33.320 --> 00:11:36.600 Because the planet is tilted on its side, the 00:11:36.600 --> 00:11:39.779 rings are tilted with it. So from Earth, over 00:11:39.779 --> 00:11:42.980 decades we see the ring system dramatically change 00:11:42.980 --> 00:11:46.419 orientation. Sometimes they're wide open and 00:11:46.419 --> 00:11:49.539 visible, and other times we see them nearly edge 00:11:49.539 --> 00:11:53.480 on and they almost disappear. During Uranus's 00:11:53.480 --> 00:11:57.519 equinox, which happens only twice every 84 Earth 00:11:57.519 --> 00:12:01.019 years, the sun shines directly on the ring plane. 00:12:01.309 --> 00:12:04.029 producing unusual lighting effects and stirring 00:12:04.029 --> 00:12:08.490 up dynamic changes in the system. Voyager 2 gave 00:12:08.490 --> 00:12:12.370 us our only close -up look in 1986, and at the 00:12:12.370 --> 00:12:16.190 time the rings looked simple and sparse. But 00:12:16.190 --> 00:12:19.049 modern observations from the Hubble Space Telescope 00:12:19.049 --> 00:12:22.370 and large ground -based telescopes have revealed 00:12:22.370 --> 00:12:26.009 faint dusty components and more complex structure 00:12:26.009 --> 00:12:29.259 than Voyager initially detected. There's never 00:12:29.259 --> 00:12:32.879 been a return mission to Uranus. We know considerably 00:12:32.879 --> 00:12:35.480 more about it than we did before the Voyager 00:12:35.480 --> 00:12:39.419 flyby, but much of it has remained a pale turquoise 00:12:39.419 --> 00:12:43.500 mystery. At nearly 2 billion miles away, the 00:12:43.500 --> 00:12:46.620 sun is just a bright point of light at Uranus. 00:12:47.100 --> 00:12:51.500 And Uranus moves slowly. It takes 84 Earth years 00:12:51.500 --> 00:12:55.440 to complete one orbit. That means since its discovery 00:12:55.440 --> 00:12:59.519 in 1781 by William Herschel, Uranus has only 00:12:59.519 --> 00:13:02.600 completed a little more than two full orbits 00:13:02.600 --> 00:13:07.840 around the sun. Neptune lies even farther out, 00:13:08.000 --> 00:13:12.039 nearly 3 billion miles from the sun. It was the 00:13:12.039 --> 00:13:15.039 first planet discovered by mathematics before 00:13:15.039 --> 00:13:18.860 observation. Astronomers noticed irregularities 00:13:18.860 --> 00:13:21.860 in Uranus's orbit and predicted another world 00:13:21.860 --> 00:13:24.820 must be tugging at it. They calculated where 00:13:24.820 --> 00:13:29.500 it should be. Then they looked, and in 1846 they 00:13:29.500 --> 00:13:34.899 found it. It takes Neptune 165 Earth years to 00:13:34.899 --> 00:13:38.659 complete one orbit. It completed its first full 00:13:38.659 --> 00:13:43.419 orbit since discovery in 2011. Neptune's beautiful 00:13:43.419 --> 00:13:46.700 blue color comes from methane in its atmosphere, 00:13:47.220 --> 00:13:50.679 but it's a deeper, more vivid blue than Uranus. 00:13:50.879 --> 00:13:54.279 That difference likely comes from subtle atmospheric 00:13:54.279 --> 00:13:57.740 chemistry and haze layers we still don't fully 00:13:57.740 --> 00:14:02.639 understand. Neptune is also wildly dynamic for 00:14:02.639 --> 00:14:06.039 such a distant cold world. Its winds are the 00:14:06.039 --> 00:14:08.659 fastest in the solar system, reaching more than 00:14:08.659 --> 00:14:12.960 1200 miles per hour. That's supersonic, in a 00:14:12.960 --> 00:14:16.379 place where temperatures hover around minus 350 00:14:16.379 --> 00:14:20.720 degrees Fahrenheit. Neptune radiates more heat 00:14:20.720 --> 00:14:23.519 than it receives from the Sun, much like Jupiter. 00:14:24.120 --> 00:14:28.879 Its interior is still warm from formation. Triton 00:14:28.879 --> 00:14:32.759 is Neptune's largest moon and likely a captured 00:14:32.759 --> 00:14:36.139 Kuiper belt object. It orbits backwards, which 00:14:36.139 --> 00:14:39.299 is a huge clue that it didn't form alongside 00:14:39.299 --> 00:14:43.120 Neptune. As for exploration, Neptune has been 00:14:43.120 --> 00:14:47.509 visited exactly once. Voyager 2 flew past in 00:14:47.509 --> 00:14:51.730 August 1989. It revealed the Great Dark Spot, 00:14:52.090 --> 00:14:55.509 a storm similar to Jupiter's Red Spot, along 00:14:55.509 --> 00:14:58.929 with a ring system. After that brief encounter, 00:14:59.370 --> 00:15:02.610 Voyager kept going. Since then, it's only been 00:15:02.610 --> 00:15:05.990 studied by Hubble and some ground -based observatories, 00:15:06.350 --> 00:15:11.360 leaving a lot of unanswered questions. The outer 00:15:11.360 --> 00:15:14.879 planets hold most of the mass and angular momentum 00:15:14.879 --> 00:15:18.820 of our solar system. They sculpt cometary paths. 00:15:19.200 --> 00:15:22.299 They influence the asteroid belt. They may have 00:15:22.299 --> 00:15:26.100 helped make Earth stable enough for life. And 00:15:26.100 --> 00:15:29.340 yet, in terms of direct exploration, only Jupiter 00:15:29.340 --> 00:15:32.019 and Saturn have received sustained attention. 00:15:32.799 --> 00:15:36.580 Uranus and Neptune remain frontier worlds. There 00:15:36.580 --> 00:15:39.220 are serious proposals right now for a dedicated 00:15:39.220 --> 00:15:42.200 Uranus orbiter, but nothing has been launched 00:15:42.200 --> 00:15:45.899 yet. In some ways, the outer solar system still 00:15:45.899 --> 00:15:49.460 feels like it's stuck in the 1970s. And that's 00:15:49.460 --> 00:15:52.980 astonishing. When you step outside this evening 00:15:52.980 --> 00:15:55.799 and see Jupiter and Saturn blazing in the twilight, 00:15:56.019 --> 00:15:58.620 you're looking at a system of worlds we've actually 00:15:58.620 --> 00:16:02.320 visited. And beyond it lie two giants we've barely 00:16:02.320 --> 00:16:06.620 touched. We've mapped Mars with rovers and drones. 00:16:06.659 --> 00:16:10.679 We've landed on comets, but the ice giants remain 00:16:10.679 --> 00:16:14.100 largely unexplored. That should humble us a little, 00:16:14.500 --> 00:16:17.940 and maybe excite us. As we step back from this 00:16:17.940 --> 00:16:20.820 tour of the outer planets, it's natural to ask 00:16:20.820 --> 00:16:24.299 a bigger question. Why are the worlds closest 00:16:24.299 --> 00:16:28.159 to the sun small and rocky, while the outer planets 00:16:28.159 --> 00:16:32.529 are enormous spheres of gas and ice? The answer 00:16:32.529 --> 00:16:35.049 goes all the way back to the birth of the solar 00:16:35.049 --> 00:16:39.450 system, about 4 .6 billion years ago. At that 00:16:39.450 --> 00:16:42.690 time, the young sun was surrounded by a vast 00:16:42.690 --> 00:16:46.990 rotating disk of gas and dust. Close to the sun, 00:16:47.409 --> 00:16:50.389 temperatures were extremely high. In that hot 00:16:50.389 --> 00:16:53.870 inner region, only heavy materials like iron, 00:16:54.309 --> 00:16:57.049 nickel, and rocky minerals could condense into 00:16:57.049 --> 00:17:00.830 solid grains. Lighter substances, things like 00:17:00.830 --> 00:17:04.750 water, methane, and ammonia, remained vaporized. 00:17:05.509 --> 00:17:08.430 That meant the inner planets formed from relatively 00:17:08.430 --> 00:17:11.890 limited ingredients, building small, dense, rocky 00:17:11.890 --> 00:17:15.430 worlds like Mercury, Venus, Earth, and Mars. 00:17:16.170 --> 00:17:19.250 Farther from the sun, however, temperatures dropped 00:17:19.250 --> 00:17:22.670 dramatically. Beyond a certain distance, what 00:17:22.670 --> 00:17:26.190 astronomers call the frost line, water and other 00:17:26.190 --> 00:17:30.069 compounds could freeze into solid ice. Suddenly, 00:17:30.170 --> 00:17:33.009 there was far more material available to build 00:17:33.009 --> 00:17:37.710 planets. With ice joining rock and metal, planetary 00:17:37.710 --> 00:17:40.369 embryos in the outer solar system could grow 00:17:40.369 --> 00:17:43.769 much larger. Once these growing worlds became 00:17:43.769 --> 00:17:46.890 massive enough, their gravity began pulling in 00:17:46.890 --> 00:17:49.549 the surrounding hydrogen and helium gas from 00:17:49.549 --> 00:17:52.769 the disk, ballooning into the giant planets we 00:17:52.769 --> 00:17:56.859 see today. So the solar system naturally divided 00:17:56.859 --> 00:17:59.519 itself into two very different neighborhoods 00:17:59.519 --> 00:18:03.140 The inner region gave rise to small terrestrial 00:18:03.140 --> 00:18:06.980 planets made mostly of rock and metal While the 00:18:06.980 --> 00:18:10.180 cooler outer region produced the giant planets 00:18:10.180 --> 00:18:13.460 Jupiter and Saturn with their vast envelopes 00:18:13.460 --> 00:18:16.799 of hydrogen and helium and Uranus and Neptune 00:18:16.799 --> 00:18:20.000 with interiors rich and frozen compounds like 00:18:20.000 --> 00:18:24.539 water methane and ammonia All the planets, in 00:18:24.539 --> 00:18:27.460 a way, represent the structure of the original 00:18:27.460 --> 00:18:30.920 disk that formed our solar system. It's a fossil 00:18:30.920 --> 00:18:34.099 record of temperature, chemistry, and gravity 00:18:34.099 --> 00:18:57.259 written across billions of miles of space. After 00:18:57.259 --> 00:18:59.720 a quick break, we'll be back to discuss what 00:18:59.720 --> 00:19:02.579 you can actually see in this week's sky and how 00:19:02.579 --> 00:19:05.839 to spot these distant planets for yourself. Stay 00:19:05.839 --> 00:19:21.259 with us. Welcome back. Before we get into this 00:19:21.259 --> 00:19:24.380 week's sky, I have a quick observation report. 00:19:24.680 --> 00:19:28.359 Last week, a series of SpaceX launches were carried 00:19:28.359 --> 00:19:32.380 out from Cape Canaveral to deliver Starlink satellites 00:19:32.380 --> 00:19:35.500 into orbit. Some of these launches were in the 00:19:35.500 --> 00:19:38.700 evening or early morning, which means folks along 00:19:38.700 --> 00:19:42.279 the eastern seaboard hundreds of miles away can 00:19:42.279 --> 00:19:44.960 see them soaring into orbit if conditions are 00:19:44.960 --> 00:19:48.420 right. These launches weren't even on my radar 00:19:48.420 --> 00:19:51.400 until my brother -in -law, Chris, shared a post 00:19:51.400 --> 00:19:54.690 with me on Sunday afternoon. With nothing better 00:19:54.690 --> 00:19:57.869 to do, we decided to find a nice high elevation 00:19:57.869 --> 00:20:00.509 with an eastern view of the sky and see if we 00:20:00.509 --> 00:20:04.269 could spot a Falcon 9 rocket. We arrived at the 00:20:04.269 --> 00:20:08.630 site around 940 for the nearly 10pm launch. We 00:20:08.630 --> 00:20:12.089 both had the SpaceX live feed on our phones so 00:20:12.089 --> 00:20:15.230 we could hear the countdown and launch. About 00:20:15.230 --> 00:20:18.369 30 seconds after launch, looking south, Chris 00:20:18.369 --> 00:20:21.849 thought he spotted a red dot making its way upward 00:20:21.849 --> 00:20:25.869 into the east. then we didn't see anything. Some 00:20:25.869 --> 00:20:28.470 moments passed and then to the east and some 00:20:28.470 --> 00:20:31.750 30 degrees off the horizon, we spotted a bright 00:20:31.750 --> 00:20:35.450 reddish object, which morphed subtly for a few 00:20:35.450 --> 00:20:38.470 seconds, then winked out as fast as it appeared. 00:20:39.049 --> 00:20:42.269 It didn't look like the plumes we normally associate 00:20:42.269 --> 00:20:45.650 with SpaceX launches. We think the significant 00:20:45.650 --> 00:20:48.990 cloud cover may have affected our view, but based 00:20:48.990 --> 00:20:52.130 on Chris's initial observation and the direction 00:20:52.130 --> 00:20:54.640 it was heading, We're pretty certain we saw the 00:20:54.640 --> 00:20:58.500 rocket, 20 stories of fire and fury climbing 00:20:58.500 --> 00:21:02.859 into space at 17 ,000 miles per hour. Several 00:21:02.859 --> 00:21:05.720 days later, another Falcon took flight in the 00:21:05.720 --> 00:21:08.779 pre -dawn hours, and local observers captured 00:21:08.779 --> 00:21:11.859 some really stunning images of the rocket's plume 00:21:11.859 --> 00:21:15.759 as it blasted across the sky, backlit high in 00:21:15.759 --> 00:21:18.660 the atmosphere by the sun before it peeked over 00:21:18.660 --> 00:21:22.599 the horizon. Sadly, I wasn't awake for that launch. 00:21:23.000 --> 00:21:25.900 From now on, I'm going to make it a point to 00:21:25.900 --> 00:21:28.200 routinely check out what's launching from the 00:21:28.200 --> 00:21:32.119 Cape, using a website like Space Flight Now to 00:21:32.119 --> 00:21:35.119 see what's on deck. I'll include a link to that 00:21:35.119 --> 00:21:38.720 in the show notes. If there's an evening or nighttime 00:21:38.720 --> 00:21:41.319 launch window and you live in the viewable zone, 00:21:41.500 --> 00:21:44.240 it could make for a nice observation or even 00:21:44.240 --> 00:21:47.819 a photo op. Keep in mind the Kennedy Space Center 00:21:47.819 --> 00:21:51.690 isn't the only NASA launch pad. West coasters 00:21:51.690 --> 00:21:55.009 can try viewing rockets from Vandenberg Space 00:21:55.009 --> 00:21:58.829 Force Base in California. Farther up the East 00:21:58.829 --> 00:22:02.009 Coast, Wallops Flight Facility on the coast of 00:22:02.009 --> 00:22:05.730 Virginia is used for supply missions to the ISS. 00:22:06.569 --> 00:22:10.369 Alaska has a spaceport, and SpaceX's private 00:22:10.369 --> 00:22:14.440 launch site is in South Texas. There's surprisingly 00:22:14.440 --> 00:22:18.579 a lot of rocket action, so keep an eye on spaceflight 00:22:18.579 --> 00:22:21.319 now and maybe you can catch a launch from the 00:22:21.319 --> 00:22:24.440 Cape or from one of these alternate locations. 00:22:31.019 --> 00:22:33.900 Now, let's see what's in the sky above our own 00:22:33.900 --> 00:22:37.559 backyard this week. First, a quick note about 00:22:37.559 --> 00:22:41.319 daylight saving time. Clocks sprung forward one 00:22:41.319 --> 00:22:44.299 hour this morning. That pushes darkness later 00:22:44.299 --> 00:22:47.880 into the evening. Your best deep sky observing 00:22:47.880 --> 00:22:51.400 window will now start later after sunset, even 00:22:51.400 --> 00:22:54.759 as overall night length slowly increases toward 00:22:54.759 --> 00:22:58.980 the spring equinox on March 20. This week the 00:22:58.980 --> 00:23:02.099 moon is still in its waning gibbous to waning 00:23:02.099 --> 00:23:05.940 crescent phase. By March 14, it's a thin crescent 00:23:05.940 --> 00:23:09.400 with about 20 % illumination. Perfect for viewing 00:23:09.400 --> 00:23:12.500 surface detail near the terminator with binoculars 00:23:12.500 --> 00:23:16.519 or a telescope. After sunset in the western sky, 00:23:17.000 --> 00:23:20.059 brilliant Venus dominates low over the horizon. 00:23:20.640 --> 00:23:23.819 It's the brightest star you'll see after dusk. 00:23:24.059 --> 00:23:26.700 And early in the week you might spot Saturn just 00:23:26.700 --> 00:23:29.859 above or beside it. A visual pairing that will 00:23:29.859 --> 00:23:32.920 linger near the western horizon for several evenings 00:23:32.920 --> 00:23:37.359 as the planets slowly separate. A pair of binoculars 00:23:37.359 --> 00:23:40.599 will show them together easily, and around tonight 00:23:40.599 --> 00:23:44.559 or tomorrow that conjunction is tightest. In 00:23:44.559 --> 00:23:47.619 the southern evening sky, high above the horizon, 00:23:48.099 --> 00:23:51.359 Jupiter shines like a beacon. It's visible well 00:23:51.359 --> 00:23:54.200 after dark at this time of year and doesn't set 00:23:54.200 --> 00:23:57.559 until the late night hours. Its steady bright 00:23:57.559 --> 00:24:00.500 light makes it excellent for telescopic views. 00:24:00.900 --> 00:24:04.519 The Galilean moons and cloud belts are easy pickings. 00:24:04.839 --> 00:24:08.180 Mercury will be very low after sunset early in 00:24:08.180 --> 00:24:11.460 this window and quickly lost to twilight glow. 00:24:12.160 --> 00:24:15.039 It re -emerges in the morning sky later in March. 00:24:15.799 --> 00:24:18.839 Mars remains too close to the Sun for effective 00:24:18.839 --> 00:24:22.960 evening observing right now. Uranus is technically 00:24:22.960 --> 00:24:26.240 still placed in western Taurus and can be tracked 00:24:26.240 --> 00:24:29.700 down in binoculars or a small scope if the moon 00:24:29.700 --> 00:24:33.230 hasn't risen and your sky is dark. But Neptune 00:24:33.230 --> 00:24:35.789 is too close to conjunction with the Sun to be 00:24:35.789 --> 00:24:39.750 seen this week. Now let's talk deep sky objects. 00:24:40.470 --> 00:24:43.309 March evenings are rich with open star clusters 00:24:43.309 --> 00:24:46.670 and faint nebula that reward patients and optics, 00:24:47.029 --> 00:24:50.849 especially once the moon sets. The Hyades cluster 00:24:50.849 --> 00:24:54.650 near Aldebaran and Taurus is a sprawling binocular 00:24:54.650 --> 00:24:58.329 -friendly grouping. Look for the broad V of stars 00:24:58.329 --> 00:25:01.859 that makes up the head of the bull. The Rosette 00:25:01.859 --> 00:25:05.380 nebula and its embedded cluster in Monoceros 00:25:05.380 --> 00:25:09.000 is a favorite for long exposures and narrow band 00:25:09.000 --> 00:25:12.500 imaging. A pair of binoculars under dark skies 00:25:12.500 --> 00:25:15.359 will show the cluster and a camera will begin 00:25:15.359 --> 00:25:19.440 to tease out nebulosity. The Beehive cluster 00:25:19.440 --> 00:25:23.839 M44 in Cancer sits higher in the late evening 00:25:23.839 --> 00:25:27.579 once the moon dips below the horizon. This object 00:25:27.579 --> 00:25:30.640 is beautiful through small scopes and even in 00:25:30.640 --> 00:25:34.480 urban skies. While there's no major meteor shower 00:25:34.480 --> 00:25:37.619 peaking this week, a few minor streams may be 00:25:37.619 --> 00:25:41.059 detectable after midnight under truly dark skies. 00:25:41.859 --> 00:25:44.640 Finally, don't forget the spring constellations 00:25:44.640 --> 00:25:48.519 rising in the east late evening. Leo, with its 00:25:48.519 --> 00:25:52.259 graceful sickle, and regal regulus, and Cancer 00:25:52.259 --> 00:25:55.819 just above, are home to loose stellar groupings. 00:25:56.160 --> 00:25:58.940 These aren't the obvious constellations like 00:25:58.940 --> 00:26:02.559 Orion or Ursa Major, but they'll reward viewers 00:26:02.559 --> 00:26:10.599 who take time with their charts and optics. For 00:26:10.599 --> 00:26:12.980 this week's book club segment, we're looking 00:26:12.980 --> 00:26:17.099 at chapters 6 and 7 of Nightwatch, covering the 00:26:17.099 --> 00:26:20.809 deep sky and the planets. And what I appreciate 00:26:20.809 --> 00:26:23.849 most about these chapters is that Terrence Dickinson 00:26:23.849 --> 00:26:26.109 continues what he's done throughout the book. 00:26:26.529 --> 00:26:30.630 He manages expectations. In chapter 6, when he 00:26:30.630 --> 00:26:34.349 describes deep sky objects like galaxies, nebula, 00:26:34.630 --> 00:26:37.829 and globular clusters, he tells you plainly what 00:26:37.829 --> 00:26:40.970 they actually look like in the eyepiece. They're 00:26:40.970 --> 00:26:44.589 dim, subtle, often colorless, and that's just 00:26:44.589 --> 00:26:48.759 how our eyes work. Under low light, our eyes 00:26:48.759 --> 00:26:53.140 rely mostly on rod cells. Rods are incredibly 00:26:53.140 --> 00:26:55.920 sensitive to faint light, which is why they allow 00:26:55.920 --> 00:26:58.660 us to see these ghostly smudges in the first 00:26:58.660 --> 00:27:02.819 place. But rods don't detect color well. The 00:27:02.819 --> 00:27:06.420 cone cells that do perceive color require much 00:27:06.420 --> 00:27:09.390 brighter light to activate. So when you look 00:27:09.390 --> 00:27:12.769 at the Orion Nebula or the Andromeda Galaxy through 00:27:12.769 --> 00:27:15.210 a telescope, you're not seeing the saturated 00:27:15.210 --> 00:27:18.990 pinks and blues of astrophotography. You're seeing 00:27:18.990 --> 00:27:21.829 what the human visual system can gather in a 00:27:21.829 --> 00:27:25.549 fraction of a second. A camera can collect photons 00:27:25.549 --> 00:27:29.690 for minutes. It can stack exposures for hours. 00:27:30.170 --> 00:27:34.640 Your retina resets continuously. Dickinson explains 00:27:34.640 --> 00:27:37.579 this, and I think that's crucial. I think new 00:27:37.579 --> 00:27:40.500 astronomers expect the sky to look like processed 00:27:40.500 --> 00:27:44.839 long exposure images. But visual astronomy is 00:27:44.839 --> 00:27:48.259 quieter than that. It's about contrast, texture, 00:27:48.500 --> 00:27:51.700 and shape. It's about learning to recognize faint 00:27:51.700 --> 00:27:55.119 structure at the edge of perception. And then 00:27:55.119 --> 00:27:57.579 Dickinson gives us something very practical. 00:27:58.039 --> 00:28:02.460 Maps. The deep sky charts in chapter 6 are clean, 00:28:02.859 --> 00:28:05.960 readable, and focused. They highlight specific 00:28:05.960 --> 00:28:09.700 objects. They indicate magnitude. They note what 00:28:09.700 --> 00:28:12.900 size instrument might be needed. They help you 00:28:12.900 --> 00:28:15.720 plan a session instead of overwhelming you with 00:28:15.720 --> 00:28:19.440 thousands of targets. There's something philosophical 00:28:19.440 --> 00:28:22.380 there. He's not encouraging you to conquer the 00:28:22.380 --> 00:28:25.160 sky. He's encouraging you to spend time with 00:28:25.160 --> 00:28:28.980 it. Then in chapter 7, when he turns to the planets, 00:28:29.059 --> 00:28:32.500 he does something similar. Again, he calibrates 00:28:32.500 --> 00:28:36.720 expectations. Saturn will not look like a glossy 00:28:36.720 --> 00:28:40.819 NASA poster. Mars won't resemble a spacecraft 00:28:40.819 --> 00:28:45.099 mosaic. Jupiter's belts may be subtle. Features 00:28:45.099 --> 00:28:48.539 will shift from night to night. And that's the 00:28:48.539 --> 00:28:52.759 point. Planets reward repeated observation. You 00:28:52.759 --> 00:28:55.839 begin to notice the tilt of Saturn's rings changing 00:28:55.839 --> 00:29:00.460 over years, the shrinking and expanding of Mars's 00:29:00.460 --> 00:29:04.240 polar caps, the steady dance of Jupiter's moons. 00:29:04.819 --> 00:29:07.779 Patience is the key here. I think both of these 00:29:07.779 --> 00:29:11.339 chapters serve as nice companions to this podcast, 00:29:11.880 --> 00:29:14.140 especially the chapter on the planets, since 00:29:14.140 --> 00:29:17.539 we've been discussing them all month long. We 00:29:17.539 --> 00:29:20.779 mention Deep Sky objects on nearly every episode, 00:29:21.140 --> 00:29:23.980 and while smartphone apps and computer databases 00:29:23.980 --> 00:29:27.400 make it easy to locate and track these objects, 00:29:27.920 --> 00:29:31.180 those great maps included in Nightwatch are really 00:29:31.180 --> 00:29:34.059 helpful for planning and laying out what's what 00:29:34.059 --> 00:29:37.059 and where it's located in relation to common 00:29:37.059 --> 00:29:40.440 constellations. We'll be back in two weeks with 00:29:40.440 --> 00:29:48.700 a discussion on the next two chapters. That's 00:29:48.700 --> 00:29:50.920 going to do it for this week. If you found this 00:29:50.920 --> 00:29:53.339 episode interesting, please share it with a friend 00:29:53.339 --> 00:29:56.019 who might enjoy it. The easiest way to do that 00:29:56.019 --> 00:29:59.480 is by sending folks to our website, StarTrails 00:29:59.480 --> 00:30:02.839 .show. And if you'd like to support the show, 00:30:03.079 --> 00:30:05.400 use the link on the site to buy me a coffee. 00:30:05.759 --> 00:30:09.460 That really helps. Be sure to follow Star Trails 00:30:09.460 --> 00:30:12.740 on Blue Sky and YouTube. Links are in the show 00:30:12.740 --> 00:30:15.799 notes. Until we meet again beneath the stars. 00:30:16.079 --> 00:30:17.440 Clear skies everyone!