WEBVTT 00:00:07.759 --> 00:00:12.099 In August of 2006, a group of astronomers gathered 00:00:12.099 --> 00:00:15.720 in Prague to make a decision. A vote was taken, 00:00:16.100 --> 00:00:20.339 and with that vote, a planet died. Pluto, the 00:00:20.339 --> 00:00:23.399 ninth planet many of us grew up memorizing in 00:00:23.399 --> 00:00:27.579 school, was suddenly gone. Demoted, reclassified, 00:00:27.960 --> 00:00:31.940 and stripped of its planetary status. The story 00:00:31.940 --> 00:00:35.740 of Pluto has always been complex. This was a 00:00:35.740 --> 00:00:38.859 world predicted before it was seen, discovered 00:00:38.859 --> 00:00:42.740 by a farm boy who loved astronomy and named by 00:00:42.740 --> 00:00:47.020 an 11 -year -old girl. And decades after its 00:00:47.020 --> 00:00:50.640 supposed downfall, a spacecraft arrived to reveal 00:00:50.640 --> 00:00:55.000 something extraordinary. Tonight, we reopen the 00:00:55.000 --> 00:00:59.460 case. My name is Drew, and this is Star Trails. 00:01:06.610 --> 00:01:09.230 Howdy stargazers and welcome to this episode 00:01:09.230 --> 00:01:12.349 of Star Trails for the week of March the 15th 00:01:12.349 --> 00:01:15.909 through the 21st. This week we look at the discovery 00:01:15.909 --> 00:01:20.510 and life of our former ninth planet, Pluto. Its 00:01:20.510 --> 00:01:24.269 murder nearly two decades ago, and its rebirth 00:01:24.269 --> 00:01:27.049 as one of the most intriguing outposts of our 00:01:27.049 --> 00:01:30.189 solar system. Later in the show, we'll see what's 00:01:30.189 --> 00:01:32.920 happening in this week's sky. Whether you're 00:01:32.920 --> 00:01:35.560 tuning in from the backyard or the balcony, I'm 00:01:35.560 --> 00:01:38.200 glad you're here. So grab a comfortable spot 00:01:38.200 --> 00:01:50.799 under the night sky and let's get started. Tonight 00:01:50.799 --> 00:01:54.340 we're opening a case file. Not a criminal case, 00:01:54.439 --> 00:01:58.000 but a cosmic one. And this story has all the 00:01:58.000 --> 00:02:01.159 elements of a good mystery. There are predictions, 00:02:01.540 --> 00:02:05.299 a long search, a young discoverer, a controversial 00:02:05.299 --> 00:02:09.039 trial, and years later, an unexpected redemption. 00:02:10.060 --> 00:02:12.780 So tonight, we're going to investigate what might 00:02:12.780 --> 00:02:16.620 be the strangest planetary story ever told, the 00:02:16.620 --> 00:02:26.900 case of Pluto. Our story begins in the late 1800s. 00:02:27.129 --> 00:02:30.629 Astronomers studying the orbit of Uranus noticed 00:02:30.629 --> 00:02:34.090 something strange. The planet wasn't exactly 00:02:34.090 --> 00:02:37.270 where it should have been. Its motion suggested 00:02:37.270 --> 00:02:40.669 that something unseen, something massive, was 00:02:40.669 --> 00:02:43.150 tugging on it from farther out in the solar system. 00:02:44.050 --> 00:02:47.870 This had happened once before. In fact, the planet 00:02:47.870 --> 00:02:51.129 Neptune had been discovered precisely this way, 00:02:51.610 --> 00:02:54.650 predicted mathematically before anyone ever saw 00:02:54.650 --> 00:02:58.050 it through a telescope. So naturally, astronomers 00:02:58.050 --> 00:03:01.069 wondered, was there another planet out there? 00:03:01.509 --> 00:03:04.810 One more world lurking in the darkness beyond 00:03:04.810 --> 00:03:09.050 Neptune. This hypothetical object became known 00:03:09.050 --> 00:03:12.889 as Planet X, and one man became obsessed with 00:03:12.889 --> 00:03:17.569 finding it. His name was Percival Lowell. Lowell 00:03:17.569 --> 00:03:20.169 was a wealthy astronomer who founded the Lowell 00:03:20.169 --> 00:03:24.539 Observatory in Flagstaff, Arizona. Today, the 00:03:24.539 --> 00:03:27.539 observatory is famous for one particular discovery, 00:03:27.979 --> 00:03:30.919 but in Lowell's time it was built largely for 00:03:30.919 --> 00:03:36.280 a single purpose, to find Planet X. Lowell calculated 00:03:36.280 --> 00:03:39.360 where this mysterious world might be hiding and 00:03:39.360 --> 00:03:42.580 began photographing regions of the sky, searching 00:03:42.580 --> 00:03:45.199 for something that moved against the background 00:03:45.199 --> 00:03:49.000 stars. But the task was enormous because the 00:03:49.000 --> 00:03:52.569 sky is vast. and the planet, if it existed, would 00:03:52.569 --> 00:03:56.770 be incredibly faint. Lowell never found it. He 00:03:56.770 --> 00:04:00.949 died in 1916. And for a while, the case went 00:04:00.949 --> 00:04:04.909 cold. More than a decade later, the investigation 00:04:04.909 --> 00:04:07.509 resumed, and the man who picked up the search 00:04:07.509 --> 00:04:11.250 was not a famous scientist. He was a farm kid 00:04:11.250 --> 00:04:15.990 from Kansas named Clyde Tombow. Tom Bow had grown 00:04:15.990 --> 00:04:19.009 up building telescopes out of spare tractor parts 00:04:19.009 --> 00:04:21.790 and studying the night sky from his family's 00:04:21.790 --> 00:04:25.050 farm. He eventually sent detailed drawings of 00:04:25.050 --> 00:04:28.889 Mars and Jupiter to Lowell Observatory. The staff 00:04:28.889 --> 00:04:32.490 were impressed, so they offered him a job. His 00:04:32.490 --> 00:04:35.990 task was simple. Photograph the sky and look 00:04:35.990 --> 00:04:39.529 for something moving. To do this, Tom Bow used 00:04:39.529 --> 00:04:43.240 a machine called a Blink Comparator. If you've 00:04:43.240 --> 00:04:46.360 ever flipped between two nearly identical photos 00:04:46.360 --> 00:04:49.040 looking for the difference, you already understand 00:04:49.040 --> 00:04:52.779 the idea. Two photographic plates of the same 00:04:52.779 --> 00:04:56.180 patch of sky are placed into the machine. Then 00:04:56.180 --> 00:04:59.279 the device rapidly switches your view back and 00:04:59.279 --> 00:05:03.180 forth between them. The stars remain fixed, but 00:05:03.180 --> 00:05:06.279 anything moving, like a comet, asteroid, or a 00:05:06.279 --> 00:05:11.470 planet, jumps back and forth. For months, Tom 00:05:11.470 --> 00:05:14.569 Bow stared into that machine, scanning thousands 00:05:14.569 --> 00:05:19.149 upon thousands of stars. Then, on February 18, 00:05:19.629 --> 00:05:23.970 1930, he saw it. A tiny speck of light, not much 00:05:23.970 --> 00:05:27.110 larger than a speck of dust, moving between two 00:05:27.110 --> 00:05:31.110 photographs taken weeks apart. Tom Bow, just 00:05:31.110 --> 00:05:36.050 24 years old, had discovered a new world. See, 00:05:36.110 --> 00:05:39.259 when I took the photographs, I had no idea. that 00:05:39.259 --> 00:05:42.420 put his image on those plates. This is Clyde 00:05:42.420 --> 00:05:46.920 Tombaugh in an interview recorded in 1991. Factors 00:05:46.920 --> 00:05:48.740 several weeks later, when I got to that pair, 00:05:49.459 --> 00:05:51.639 and I encountered as I'm going through all these 00:05:51.639 --> 00:05:54.259 alternating views of star fields, and here's 00:05:54.259 --> 00:05:56.680 one that shifted position by the right amount. 00:05:56.720 --> 00:05:59.420 Now I had figured out beforehand that if there 00:05:59.420 --> 00:06:03.500 was a Planet X, how would I recognize it if I 00:06:03.500 --> 00:06:05.220 encountered it, you see? So I thought all this 00:06:05.220 --> 00:06:07.899 out beforehand. And so when it came there, it 00:06:07.899 --> 00:06:10.980 was instantly I realized I had found a planet 00:06:10.980 --> 00:06:13.180 beyond the orbit of Neptune by the amount of 00:06:13.180 --> 00:06:15.220 shift. I knew the scale of the plates. I knew 00:06:15.220 --> 00:06:17.139 the interval. It's just a matter of geometry. 00:06:17.699 --> 00:06:19.860 That was the most instantaneous sail you could 00:06:19.860 --> 00:06:23.180 imagine. It just electrified me. And that was 00:06:23.180 --> 00:06:30.519 the 18th of February, 1930. The discovery electrified 00:06:30.519 --> 00:06:33.800 the world too. Newspapers called it the ninth 00:06:33.800 --> 00:06:36.939 planet, and suddenly everyone wanted to name 00:06:36.939 --> 00:06:40.379 it. Thousands of suggestions poured in from around 00:06:40.379 --> 00:06:43.160 the globe, but the winning idea came from an 00:06:43.160 --> 00:06:47.120 11 -year -old girl in Oxford named Venetia Burney. 00:06:47.759 --> 00:06:51.720 Her suggestion? Pluto, the Roman god of the underworld. 00:06:52.620 --> 00:06:56.339 It was a perfect name. Pluto ruled a dark, distant 00:06:56.339 --> 00:06:59.540 realm far from the sun. and the first two letters, 00:06:59.680 --> 00:07:03.600 P and L, also honored Percival Lowell, whose 00:07:03.600 --> 00:07:07.379 search had started the whole investigation. Later 00:07:07.379 --> 00:07:10.360 that same year, Walt Disney introduced a new 00:07:10.360 --> 00:07:14.540 character, Mickey Mouse's dog. His name was Pluto, 00:07:15.220 --> 00:07:17.879 and he was almost certainly named after the newly 00:07:17.879 --> 00:07:20.600 discovered planet that had captured the world's 00:07:20.600 --> 00:07:24.339 imagination. Not bad for a frozen world billions 00:07:24.339 --> 00:07:31.500 of miles away. For decades, Pluto remained mysterious. 00:07:31.860 --> 00:07:34.959 First, it's incredibly distant. Its orbit takes 00:07:34.959 --> 00:07:39.480 it from about 2 .7 to 4 .6 billion miles from 00:07:39.480 --> 00:07:44.480 the Sun. One trip around the Sun takes 248 Earth 00:07:44.480 --> 00:07:47.720 years, which means Pluto has not even completed 00:07:47.720 --> 00:07:50.439 a full orbit since the day it was discovered. 00:07:52.040 --> 00:07:55.750 Its orbit is also tilted and elongated. unlike 00:07:55.750 --> 00:07:58.829 the nearly circular paths of the major planets. 00:07:59.449 --> 00:08:02.470 Sometimes Pluto actually comes closer to the 00:08:02.470 --> 00:08:06.889 Sun than Neptune. That happened from 1979 to 00:08:06.889 --> 00:08:11.529 1999. Despite that overlap, the two worlds never 00:08:11.529 --> 00:08:14.850 collide because Pluto is locked in a three -to 00:08:14.850 --> 00:08:19.110 -two orbital resonance with Neptune. Pluto is 00:08:19.110 --> 00:08:24.870 also tiny. It's just 2 ,377 kilometers across. 00:08:25.079 --> 00:08:28.839 making it smaller than Earth's moon. Its surface 00:08:28.839 --> 00:08:32.539 is made of exotic ices, nitrogen, methane, and 00:08:32.539 --> 00:08:35.919 water ice, existing at temperatures around minus 00:08:35.919 --> 00:08:46.600 375 degrees Fahrenheit or colder. For much of 00:08:46.600 --> 00:08:50.019 the 20th century, astronomers assumed Pluto was 00:08:50.019 --> 00:08:54.360 probably a cold, inactive world. a lonely outpost 00:08:54.360 --> 00:08:57.600 at the edge of the solar system. But then another 00:08:57.600 --> 00:09:03.100 discovery complicated the story. In 1978, astronomer 00:09:03.100 --> 00:09:06.019 James Christie noticed something strange while 00:09:06.019 --> 00:09:09.620 studying telescope images of Pluto. The planet 00:09:09.620 --> 00:09:12.980 appeared slightly elongated, almost as if there 00:09:12.980 --> 00:09:16.799 were a bump sticking out of one side. At first, 00:09:16.860 --> 00:09:19.299 he assumed it was an error in the image, but 00:09:19.299 --> 00:09:22.539 the bump kept appearing. and its position kept 00:09:22.539 --> 00:09:25.779 changing. Christie realized what he was seeing. 00:09:26.259 --> 00:09:31.039 Pluto had a moon. The moon was named Charon after 00:09:31.039 --> 00:09:34.019 the fairy man of the dead in Greek mythology 00:09:34.019 --> 00:09:38.139 who carried souls across the river Styx to Pluto's 00:09:38.139 --> 00:09:42.120 realm. Charon turned out to be enormous relative 00:09:42.120 --> 00:09:46.240 to Pluto, about half of Pluto's diameter. So 00:09:46.240 --> 00:09:49.220 large, in fact, that the two worlds orbit a point 00:09:49.220 --> 00:09:52.639 in space between them rather than Charon simply 00:09:52.639 --> 00:09:56.440 circling Pluto. In some ways, Pluto and Charon 00:09:56.440 --> 00:09:59.659 are better described as a binary planetary system, 00:10:00.200 --> 00:10:03.559 and later observations revealed even more companions. 00:10:04.159 --> 00:10:08.159 Four smaller moons named Nix, Hydra, Kerberos, 00:10:08.460 --> 00:10:12.419 and Styx. But by this point, astronomers were 00:10:12.419 --> 00:10:15.100 beginning to notice something else, something 00:10:15.100 --> 00:10:18.620 that would eventually lead to Pluto's downfall. 00:10:22.779 --> 00:10:25.799 Beginning in the 1990s, astronomers discovered 00:10:25.799 --> 00:10:30.179 hundreds of icy bodies beyond Neptune. This region 00:10:30.179 --> 00:10:33.059 became known as the Kuiper Belt, and suddenly 00:10:33.059 --> 00:10:37.029 Pluto didn't look so unique anymore. It looked 00:10:37.029 --> 00:10:40.129 like one member of a much larger population of 00:10:40.129 --> 00:10:44.509 distant icy worlds. Then in 2005, astronomers 00:10:44.509 --> 00:10:48.090 discovered an object called Eris, roughly comparable 00:10:48.090 --> 00:10:52.169 in size to Pluto. And that forced a very uncomfortable 00:10:52.169 --> 00:10:55.809 question. If Pluto is a planet, should Eris be 00:10:55.809 --> 00:10:59.169 a planet too? And if Eris is a planet, how many 00:10:59.169 --> 00:11:02.090 more planets might we find out there? Dozens, 00:11:02.450 --> 00:11:06.700 hundreds, maybe more. In 2006, the International 00:11:06.700 --> 00:11:09.740 Astronomical Union convened a meeting in Prague 00:11:09.740 --> 00:11:14.000 to settle the issue. Astronomers debated a deceptively 00:11:14.000 --> 00:11:18.700 simple question. What is a planet? After deliberation, 00:11:18.879 --> 00:11:22.299 a new definition was adopted. To qualify as a 00:11:22.299 --> 00:11:25.879 planet, a body must orbit the sun, it must be 00:11:25.879 --> 00:11:29.899 round due to its own gravity, and it must clear 00:11:29.899 --> 00:11:34.040 its orbital neighborhood of other objects. Pluto 00:11:34.040 --> 00:11:37.860 failed that last requirement. It shares its region 00:11:37.860 --> 00:11:41.879 of space with many Kuiper Belt objects. And so 00:11:41.879 --> 00:11:45.220 the verdict came down. Pluto was no longer part 00:11:45.220 --> 00:11:48.539 of the starting lineup. It was reclassified as 00:11:48.539 --> 00:11:52.899 a dwarf planet. And many astronomers supported 00:11:52.899 --> 00:11:57.200 the decision. Among the most visible voices explaining 00:11:57.200 --> 00:12:00.740 the change to the public was astrophysicist Neil 00:12:00.740 --> 00:12:04.299 deGrasse Tyson. who had already removed Pluto 00:12:04.299 --> 00:12:07.679 from the planetary lineup at the Hayden Planetarium 00:12:07.679 --> 00:12:11.360 years earlier. But the astronomer who calls himself 00:12:11.360 --> 00:12:15.500 the real Pluto killer is Mike Brown of Caltech. 00:12:16.480 --> 00:12:19.539 Brown had spent years surveying the outer solar 00:12:19.539 --> 00:12:22.200 system and was convinced that Pluto was not a 00:12:22.200 --> 00:12:25.500 unique planet but simply a member of a much bigger 00:12:25.500 --> 00:12:30.360 population of icy bodies beyond Neptune. As his 00:12:30.360 --> 00:12:33.539 team began discovering more and more large Kuiper 00:12:33.539 --> 00:12:37.320 Belt objects, Brown openly argued that astronomers 00:12:37.320 --> 00:12:40.259 would eventually have to face a choice. Either 00:12:40.259 --> 00:12:44.360 accept dozens of new planets, or rethink Pluto's 00:12:44.360 --> 00:12:49.039 status entirely. After 76 years of glory, Pluto 00:12:49.039 --> 00:12:51.480 was demoted from being considered one of nine 00:12:51.480 --> 00:12:54.820 planets in our solar system to just a dwarf planet. 00:12:55.139 --> 00:12:56.919 And the scientists who made the discovery will 00:12:56.919 --> 00:12:59.820 always be known as the man who killed Pluto. 00:13:00.000 --> 00:13:02.440 Pluto's not a planet because it's part of this 00:13:02.440 --> 00:13:05.879 vast swarm of bodies out beyond Neptune in what 00:13:05.879 --> 00:13:08.159 we now call the Kuiper belt. There are thousands, 00:13:08.539 --> 00:13:10.940 millions of objects out there of which Pluto 00:13:10.940 --> 00:13:14.059 is only the second most massive. Mike Brown, 00:13:14.159 --> 00:13:16.350 a professor at Caltech, says he We will never 00:13:16.350 --> 00:13:19.970 hear the end of it. Mostly it was adults thinking 00:13:19.970 --> 00:13:24.470 of their childhood memory that were upset. Brown's 00:13:24.470 --> 00:13:27.289 discoveries were what truly pushed the debate 00:13:27.289 --> 00:13:30.350 to its breaking point. But for many Pluto fans, 00:13:30.789 --> 00:13:33.190 Tyson became the public face of the decision. 00:13:33.850 --> 00:13:36.809 Here he is chatting with Stephen Colbert about 00:13:36.809 --> 00:13:44.580 being an accessory to the ruling. discovered 00:13:44.580 --> 00:13:46.820 the objects in the outer solar system that forced 00:13:46.820 --> 00:13:49.740 that vote. In fact, he's guilty. In fact, his 00:13:49.740 --> 00:13:53.980 Twitter handle is called Pluto Killer. He admits 00:13:53.980 --> 00:13:56.110 it. Who is this Mike Brown you're throwing under 00:13:56.110 --> 00:13:59.769 the bus right now? Under the space bus. He put 00:13:59.769 --> 00:14:01.409 himself under the bus. I'm pointing it out. But 00:14:01.409 --> 00:14:03.470 here's the thing is that now some of your buddies 00:14:03.470 --> 00:14:08.350 at NASA want to reinstate Pluto as a planet because 00:14:08.350 --> 00:14:10.529 they want the designation of planet to be closer 00:14:10.529 --> 00:14:14.389 to people's intuition rather than some arbitrary 00:14:14.389 --> 00:14:17.990 scientific designation. Okay. They should just 00:14:17.990 --> 00:14:21.360 like get over it. OK. Why do you think people 00:14:21.360 --> 00:14:23.860 want to name it a planet? Pluto had it coming 00:14:23.860 --> 00:14:27.059 from the beginning. It was never really belong. 00:14:27.179 --> 00:14:30.320 Pluto's orbit crosses that of another planet. 00:14:30.360 --> 00:14:33.440 That's no kind of behavior for a planet. No! 00:14:34.299 --> 00:14:36.539 You got to stay in your lane. Stay in your lane! 00:14:36.659 --> 00:14:41.899 Stay in your lane! All right, OK. No! Clyde Tombaugh 00:14:41.899 --> 00:14:46.539 passed away in 1997, but his connection to Pluto 00:14:46.539 --> 00:14:52.320 didn't end there. When NASA launched the spacecraft 00:14:52.320 --> 00:14:56.779 New Horizons in 2006, the very same year Pluto 00:14:56.779 --> 00:15:00.740 was demoted, a small portion of Tom Bow's ashes 00:15:00.740 --> 00:15:04.580 was placed aboard the spacecraft. Nine years 00:15:04.580 --> 00:15:08.600 later, that spacecraft arrived at Pluto, symbolically 00:15:08.600 --> 00:15:11.559 carrying its discoverer to the world he had found. 00:15:12.240 --> 00:15:14.720 Few scientists in history have ever traveled, 00:15:14.879 --> 00:15:18.220 at least in spirit, to visit their own discovery. 00:15:24.840 --> 00:15:28.259 When New Horizons flew past Pluto on July the 00:15:28.259 --> 00:15:32.740 14th 2015, the images it sent back stunned the 00:15:32.740 --> 00:15:37.399 world. Pluto was not a frozen relic. It had towering 00:15:37.399 --> 00:15:40.980 mountains made of water ice, vast glaciers of 00:15:40.980 --> 00:15:44.620 frozen nitrogen, a thin blue atmosphere, and 00:15:44.620 --> 00:15:49.399 a giant heart -shaped plane. Pluto even has a 00:15:49.399 --> 00:15:52.980 strange seasonal atmosphere made mostly of nitrogen. 00:15:53.279 --> 00:15:56.220 As the dwarf planet moves farther from the Sun, 00:15:56.659 --> 00:15:59.240 that atmosphere can actually freeze and fall 00:15:59.240 --> 00:16:03.059 back to the surface like frost. Some scientists 00:16:03.059 --> 00:16:06.159 even think Pluto may hide a subsurface ocean 00:16:06.159 --> 00:16:10.940 beneath its icy crust. Against all expectations, 00:16:11.139 --> 00:16:14.399 Pluto appeared geologically active, dynamic, 00:16:14.799 --> 00:16:18.240 and alive with strange processes scientists are 00:16:18.240 --> 00:16:21.529 still trying to understand. For a world barely 00:16:21.529 --> 00:16:24.409 half the size of Earth's moon, it turned out 00:16:24.409 --> 00:16:28.309 to be astonishingly complex. And for some, that 00:16:28.309 --> 00:16:32.570 meant Pluto is a planet. You could really undercut 00:16:32.570 --> 00:16:35.110 all the planets. They're all dwarf planets because 00:16:35.110 --> 00:16:37.529 there isn't a planet that clears its entire orbit 00:16:37.529 --> 00:16:40.470 around the sun. That's former NASA Administrator 00:16:40.470 --> 00:16:43.730 Jim Bridenstine. I think the way you should define 00:16:43.730 --> 00:16:46.809 a planet... is based on its intrinsic values, 00:16:46.870 --> 00:16:49.529 not the values that constantly change like orbital 00:16:49.529 --> 00:16:52.610 dynamics. So when I think about Pluto and what 00:16:52.610 --> 00:16:54.929 we got back from New Horizons, here's what we 00:16:54.929 --> 00:17:01.070 know. Pluto has an ocean under its surface. Pluto 00:17:01.070 --> 00:17:05.650 has complex organic compounds on its surface. 00:17:06.230 --> 00:17:09.309 Pluto has a multi -layer atmosphere and Pluto 00:17:09.309 --> 00:17:12.730 has its own moons. I'm here to tell you, as the 00:17:12.730 --> 00:17:16.859 NASA administrator, I believe Pluto is a planet. 00:17:20.640 --> 00:17:24.900 Today, the verdict of 2006 still stands. Pluto 00:17:24.900 --> 00:17:28.420 remains officially classified as a dwarf planet. 00:17:29.480 --> 00:17:32.019 Every February, hundreds of people travel to 00:17:32.019 --> 00:17:35.240 northern Arizona to celebrate Pluto at the place 00:17:35.240 --> 00:17:38.119 where it was discovered, the historic Lowell 00:17:38.119 --> 00:17:41.740 Observatory. The event is called the I Heart 00:17:41.740 --> 00:17:45.299 Pluto Festival, and it's part science conference, 00:17:45.759 --> 00:17:49.039 part community celebration, and part love letter 00:17:49.039 --> 00:17:53.039 to the distant world. Visitors attend astronomy 00:17:53.039 --> 00:17:56.160 lectures, telescope demonstrations, and talks 00:17:56.160 --> 00:17:59.589 from planetary scientists. There are art exhibits, 00:17:59.990 --> 00:18:03.109 science presentations, and even a pub crawl through 00:18:03.109 --> 00:18:06.569 downtown Flagstaff, where astronomers give short 00:18:06.569 --> 00:18:23.440 talks about Pluto between stops. the man who 00:18:23.440 --> 00:18:26.000 discovered Pluto. Well the events that Lowell 00:18:26.000 --> 00:18:28.420 Observatory and Flagstaff have put on are always 00:18:28.420 --> 00:18:31.880 very important to us. We very much appreciate 00:18:31.880 --> 00:18:34.180 the honors that they have been given to my father 00:18:34.180 --> 00:18:37.920 and to his accomplishments here at Lowell Observatory 00:18:37.920 --> 00:18:40.819 and in Flagstaff. It may sound like an unusual 00:18:40.819 --> 00:18:44.440 festival but it speaks to something deeper. Pluto's 00:18:44.440 --> 00:18:47.319 discovery in 1930 was one of the great moments 00:18:47.319 --> 00:18:51.450 in American astronomy. and the city of Flagstaff 00:18:51.450 --> 00:18:54.069 still takes pride in being the place where a 00:18:54.069 --> 00:18:57.390 faint speck of light first revealed a new world. 00:18:58.069 --> 00:19:00.990 Pluto was the only planet discovered in the United 00:19:00.990 --> 00:19:05.250 States, and Americans love an underdog. Pluto 00:19:05.250 --> 00:19:08.009 being the smallest planet certainly fits the 00:19:08.009 --> 00:19:15.890 bill. If there's one lesson here, it's this. 00:19:16.170 --> 00:19:18.950 Pluto was never the end of the solar system. 00:19:19.109 --> 00:19:22.569 It's the first visible member of an entire neighborhood 00:19:22.569 --> 00:19:25.730 we hadn't discovered yet. That neighborhood is 00:19:25.730 --> 00:19:29.710 the Kuiper Belt, a vast disk of icy leftovers 00:19:29.710 --> 00:19:32.390 from the era when the planets were forming about 00:19:32.390 --> 00:19:36.490 four and a half billion years ago. The Belt begins 00:19:36.490 --> 00:19:39.829 just beyond Neptune, roughly 30 astronomical 00:19:39.829 --> 00:19:43.509 units from the Sun, and extends outward at least 00:19:43.509 --> 00:19:48.319 a 50 AU and maybe further. Pluto is the first 00:19:48.319 --> 00:19:51.599 house on the street leading out into the suburbs 00:19:51.599 --> 00:19:55.160 of our solar system. The front porch of the Kuiper 00:19:55.160 --> 00:19:59.079 Belt, perhaps. The real mystery is how many more 00:19:59.079 --> 00:20:02.440 worlds are still waiting to be found. And that 00:20:02.440 --> 00:20:05.859 makes Pluto less like a fallen planet, and more 00:20:05.859 --> 00:20:09.059 like the cosmic welcome sign to an undiscovered 00:20:09.059 --> 00:20:31.569 country. After a quick break, I'll tell you what 00:20:31.569 --> 00:20:34.170 you can expect to see in this week's night sky. 00:20:34.529 --> 00:20:50.390 Stay with us. Welcome back. Now that we've closed 00:20:50.390 --> 00:20:53.250 the case file on Pluto, let's turn our attention 00:20:53.250 --> 00:20:56.910 to the sky above us this week. Mid -March is 00:20:56.910 --> 00:21:00.569 a beautiful time for backyard astronomers. Winter's 00:21:00.569 --> 00:21:03.190 constellations are slowly slipping westward. 00:21:03.529 --> 00:21:06.309 The first hints of spring are rising in the east, 00:21:06.710 --> 00:21:09.089 and the night sky itself feels like it's in the 00:21:09.089 --> 00:21:12.910 middle of a seasonal handoff. So if you're stepping 00:21:12.910 --> 00:21:15.150 outside this week, here's what you can expect 00:21:15.150 --> 00:21:18.869 to find. We'll begin with the moon. It's moving 00:21:18.869 --> 00:21:21.289 through its waning crescent phase during most 00:21:21.289 --> 00:21:23.950 of this week. You'll see it rising in the early 00:21:23.950 --> 00:21:26.910 morning hours, appearing as a delicate, curved 00:21:26.910 --> 00:21:30.990 sliver before sunrise. The new moon arrives at 00:21:30.990 --> 00:21:34.170 week's end, leading to inky dark skies suitable 00:21:34.170 --> 00:21:38.269 for deep sky observation. And March the 20th 00:21:38.269 --> 00:21:41.730 brings another milestone. That's the vernal equinox, 00:21:41.950 --> 00:21:44.250 the official beginning of spring in the Northern 00:21:44.250 --> 00:21:47.829 Hemisphere. On this day, the Sun crosses the 00:21:47.829 --> 00:21:51.089 celestial equator and day and night become nearly 00:21:51.089 --> 00:21:54.549 equal in length. Astronomically speaking, it 00:21:54.549 --> 00:21:57.470 also means the night sky is beginning its seasonal 00:21:57.470 --> 00:22:01.009 transformation. Winter constellations like Orion 00:22:01.009 --> 00:22:04.069 and Taurus are drifting westward, while the stars 00:22:04.069 --> 00:22:07.009 of spring begin climbing into the eastern sky. 00:22:08.009 --> 00:22:10.950 If you live somewhere with reasonably dark skies, 00:22:11.210 --> 00:22:14.069 this week offers a wonderful opportunity to spot 00:22:14.069 --> 00:22:16.630 something many observers have never seen before, 00:22:17.130 --> 00:22:21.430 the zodiacal light. About 20 minutes after sunset, 00:22:21.710 --> 00:22:25.230 look toward the western horizon. Under dark conditions, 00:22:25.430 --> 00:22:28.869 you may notice a faint triangular glow rising 00:22:28.869 --> 00:22:33.160 upward along the path of the planets. This ghostly 00:22:33.160 --> 00:22:36.460 pillar of light is sunlight reflecting off millions 00:22:36.460 --> 00:22:39.779 of tiny dust particles that fill the inner solar 00:22:39.779 --> 00:22:43.700 system, leftovers from comet tails and asteroid 00:22:43.700 --> 00:22:46.799 collisions. March is one of the best times of 00:22:46.799 --> 00:22:48.960 year to see it because the angle of the solar 00:22:48.960 --> 00:22:52.420 system's plane is steep against the evening horizon 00:22:52.420 --> 00:22:55.880 near the spring equinox. If you've never seen 00:22:55.880 --> 00:22:58.579 it before, it looks almost like a faint, tilted 00:22:58.579 --> 00:23:01.660 beam of twilight reaching up into the stars. 00:23:02.740 --> 00:23:06.039 This week also offers several planets to explore. 00:23:06.720 --> 00:23:09.019 First up is Jupiter, which remains one of the 00:23:09.019 --> 00:23:11.420 brightest objects in the night sky this month. 00:23:11.880 --> 00:23:14.859 It shines prominently in the constellation Gemini, 00:23:15.299 --> 00:23:17.779 easily visible in the evening and remaining high 00:23:17.779 --> 00:23:20.980 in the sky for much of the night. If you step 00:23:20.980 --> 00:23:23.839 outside after sunset, Jupiter will likely be 00:23:23.839 --> 00:23:26.940 the first planet your eye catches. Its brightness 00:23:26.940 --> 00:23:30.940 is startling. Low in the western sky, you may 00:23:30.940 --> 00:23:33.660 still catch Venus in the evening twilight, though 00:23:33.660 --> 00:23:37.460 it sets fairly quickly. Saturn has been slipping 00:23:37.460 --> 00:23:40.299 towards the Sun's glare and is becoming difficult 00:23:40.299 --> 00:23:43.740 to observe now, lingering very low near the horizon 00:23:43.740 --> 00:23:47.630 shortly after sunset. With binoculars or a telescope, 00:23:47.710 --> 00:23:50.230 you can also try tracking down Uranus, which 00:23:50.230 --> 00:23:53.289 sits in the constellation Taurus, not far from 00:23:53.289 --> 00:23:57.289 the famous Pleiades star cluster. Through binoculars, 00:23:57.410 --> 00:24:01.230 Uranus appears as a tiny aquamarine star among 00:24:01.230 --> 00:24:05.029 the surrounding field. Meanwhile, the stars of 00:24:05.029 --> 00:24:08.589 spring are rising in the east. Look for the constellation 00:24:08.589 --> 00:24:11.670 Leo, which contains the bright star Regulus, 00:24:11.930 --> 00:24:15.460 marking the heart of the celestial lion. LEO 00:24:15.460 --> 00:24:18.039 is home to one of the most rewarding regions 00:24:18.039 --> 00:24:22.079 of the sky for telescope observers. The LEO triplet 00:24:22.079 --> 00:24:26.980 features a small group of galaxies M65, M66, 00:24:27.500 --> 00:24:33.279 and NGC 3628. Under dark skies, even modest scopes 00:24:33.279 --> 00:24:36.000 can reveal these three distant islands floating 00:24:36.000 --> 00:24:40.039 together in space, 35 million light -years away. 00:24:40.750 --> 00:24:43.809 If you're feeling adventurous, try hunting down 00:24:43.809 --> 00:24:47.450 one of the sky's most unusual deep sky objects. 00:24:48.190 --> 00:24:53.769 The Eskimo Nebula, also known as NGC 2392, sits 00:24:53.769 --> 00:24:57.190 in the constellation Gemini, not far from Jupiter. 00:24:57.970 --> 00:25:01.190 This object is a planetary nebula, a glowing 00:25:01.190 --> 00:25:05.450 shell of gas expelled by a dying star. Through 00:25:05.450 --> 00:25:08.609 a telescope it appears as a small bluish disk, 00:25:08.730 --> 00:25:11.390 and with larger instruments, observers often 00:25:11.390 --> 00:25:14.170 notice a fuzzy halo that gives it the appearance 00:25:14.170 --> 00:25:18.410 of a face framed by a parka hood, hence the nickname 00:25:18.410 --> 00:25:22.789 the Eskimo Nebula. And somewhere far beyond the 00:25:22.789 --> 00:25:25.829 reach of backyard telescopes, Pluto continues 00:25:25.829 --> 00:25:29.269 its slow journey around the Sun. We actually 00:25:29.269 --> 00:25:32.910 discussed how to view Pluto back in episode 64. 00:25:33.200 --> 00:25:36.160 So, if you have access to a massive telescope, 00:25:36.519 --> 00:25:40.039 a camera, and some very dark skies, go for it! 00:25:44.740 --> 00:25:47.240 That's going to do it for this week. If you found 00:25:47.240 --> 00:25:49.480 this episode interesting, please share it with 00:25:49.480 --> 00:25:52.279 a friend who might enjoy it. The easiest way 00:25:52.279 --> 00:25:55.180 to do that is by sending folks to our website, 00:25:55.619 --> 00:25:59.259 StarTrails .Show. And, if you'd like to support 00:25:59.259 --> 00:26:01.740 the show, use the link on the site to buy me 00:26:01.740 --> 00:26:05.259 a coffee. That really helps. Be sure to follow 00:26:05.259 --> 00:26:09.000 Star Trails on Blue Sky and YouTube. Links are 00:26:09.000 --> 00:26:11.819 in the show notes. Until we meet again beneath 00:26:11.819 --> 00:26:14.299 the stars, clear skies everyone.