Latest / Star Trails: From Backyard Astronomy to Cosmic Wonder / The Case of Pluto: Discovery, Demotion, and Redemption

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The Case of Pluto: Discovery, Demotion, and Redemption · Star Trails: From Backyard Astronomy to Cosmic Wonder

• 0:07
  In August of 2006, a group of astronomers gathered
• 0:12
  in Prague to make a decision. A vote was taken,
• 0:16
  and with that vote, a planet died. Pluto, the
• 0:20
  ninth planet many of us grew up memorizing in
• 0:23
  school, was suddenly gone. Demoted, reclassified,
• 0:27
  and stripped of its planetary status. The story
• 0:31
  of Pluto has always been complex. This was a
• 0:35
  world predicted before it was seen, discovered
• 0:38
  by a farm boy who loved astronomy and named by
• 0:42
  an 11 -year -old girl. And decades after its
• 0:47
  supposed downfall, a spacecraft arrived to reveal
• 0:50
  something extraordinary. Tonight, we reopen the
• 0:55
  case. My name is Drew, and this is Star Trails.
• 1:06
  Howdy stargazers and welcome to this episode
• 1:09
  of Star Trails for the week of March the 15th
• 1:12
  through the 21st. This week we look at the discovery
• 1:15
  and life of our former ninth planet, Pluto. Its
• 1:20
  murder nearly two decades ago, and its rebirth
• 1:24
  as one of the most intriguing outposts of our
• 1:27
  solar system. Later in the show, we'll see what's
• 1:30
  happening in this week's sky. Whether you're
• 1:32
  tuning in from the backyard or the balcony, I'm
• 1:35
  glad you're here. So grab a comfortable spot
• 1:38
  under the night sky and let's get started. Tonight
• 1:50
  we're opening a case file. Not a criminal case,
• 1:54
  but a cosmic one. And this story has all the
• 1:58
  elements of a good mystery. There are predictions,
• 2:01
  a long search, a young discoverer, a controversial
• 2:05
  trial, and years later, an unexpected redemption.
• 2:10
  So tonight, we're going to investigate what might
• 2:12
  be the strangest planetary story ever told, the
• 2:16
  case of Pluto. Our story begins in the late 1800s.
• 2:27
  Astronomers studying the orbit of Uranus noticed
• 2:30
  something strange. The planet wasn't exactly
• 2:34
  where it should have been. Its motion suggested
• 2:37
  that something unseen, something massive, was
• 2:40
  tugging on it from farther out in the solar system.
• 2:44
  This had happened once before. In fact, the planet
• 2:47
  Neptune had been discovered precisely this way,
• 2:51
  predicted mathematically before anyone ever saw
• 2:54
  it through a telescope. So naturally, astronomers
• 2:58
  wondered, was there another planet out there?
• 3:01
  One more world lurking in the darkness beyond
• 3:04
  Neptune. This hypothetical object became known
• 3:09
  as Planet X, and one man became obsessed with
• 3:12
  finding it. His name was Percival Lowell. Lowell
• 3:17
  was a wealthy astronomer who founded the Lowell
• 3:20
  Observatory in Flagstaff, Arizona. Today, the
• 3:24
  observatory is famous for one particular discovery,
• 3:27
  but in Lowell's time it was built largely for
• 3:30
  a single purpose, to find Planet X. Lowell calculated
• 3:36
  where this mysterious world might be hiding and
• 3:39
  began photographing regions of the sky, searching
• 3:42
  for something that moved against the background
• 3:45
  stars. But the task was enormous because the
• 3:49
  sky is vast. and the planet, if it existed, would
• 3:52
  be incredibly faint. Lowell never found it. He
• 3:56
  died in 1916. And for a while, the case went
• 4:00
  cold. More than a decade later, the investigation
• 4:04
  resumed, and the man who picked up the search
• 4:07
  was not a famous scientist. He was a farm kid
• 4:11
  from Kansas named Clyde Tombow. Tom Bow had grown
• 4:15
  up building telescopes out of spare tractor parts
• 4:19
  and studying the night sky from his family's
• 4:21
  farm. He eventually sent detailed drawings of
• 4:25
  Mars and Jupiter to Lowell Observatory. The staff
• 4:28
  were impressed, so they offered him a job. His
• 4:32
  task was simple. Photograph the sky and look
• 4:35
  for something moving. To do this, Tom Bow used
• 4:39
  a machine called a Blink Comparator. If you've
• 4:43
  ever flipped between two nearly identical photos
• 4:46
  looking for the difference, you already understand
• 4:49
  the idea. Two photographic plates of the same
• 4:52
  patch of sky are placed into the machine. Then
• 4:56
  the device rapidly switches your view back and
• 4:59
  forth between them. The stars remain fixed, but
• 5:03
  anything moving, like a comet, asteroid, or a
• 5:06
  planet, jumps back and forth. For months, Tom
• 5:11
  Bow stared into that machine, scanning thousands
• 5:14
  upon thousands of stars. Then, on February 18,
• 5:19
  1930, he saw it. A tiny speck of light, not much
• 5:23
  larger than a speck of dust, moving between two
• 5:27
  photographs taken weeks apart. Tom Bow, just
• 5:31
  24 years old, had discovered a new world. See,
• 5:36
  when I took the photographs, I had no idea. that
• 5:39
  put his image on those plates. This is Clyde
• 5:42
  Tombaugh in an interview recorded in 1991. Factors
• 5:46
  several weeks later, when I got to that pair,
• 5:49
  and I encountered as I'm going through all these
• 5:51
  alternating views of star fields, and here's
• 5:54
  one that shifted position by the right amount.
• 5:56
  Now I had figured out beforehand that if there
• 5:59
  was a Planet X, how would I recognize it if I
• 6:03
  encountered it, you see? So I thought all this
• 6:05
  out beforehand. And so when it came there, it
• 6:07
  was instantly I realized I had found a planet
• 6:10
  beyond the orbit of Neptune by the amount of
• 6:13
  shift. I knew the scale of the plates. I knew
• 6:15
  the interval. It's just a matter of geometry.
• 6:17
  That was the most instantaneous sail you could
• 6:19
  imagine. It just electrified me. And that was
• 6:23
  the 18th of February, 1930. The discovery electrified
• 6:30
  the world too. Newspapers called it the ninth
• 6:33
  planet, and suddenly everyone wanted to name
• 6:36
  it. Thousands of suggestions poured in from around
• 6:40
  the globe, but the winning idea came from an
• 6:43
  11 -year -old girl in Oxford named Venetia Burney.
• 6:47
  Her suggestion? Pluto, the Roman god of the underworld.
• 6:52
  It was a perfect name. Pluto ruled a dark, distant
• 6:56
  realm far from the sun. and the first two letters,
• 6:59
  P and L, also honored Percival Lowell, whose
• 7:03
  search had started the whole investigation. Later
• 7:07
  that same year, Walt Disney introduced a new
• 7:10
  character, Mickey Mouse's dog. His name was Pluto,
• 7:15
  and he was almost certainly named after the newly
• 7:17
  discovered planet that had captured the world's
• 7:20
  imagination. Not bad for a frozen world billions
• 7:24
  of miles away. For decades, Pluto remained mysterious.
• 7:31
  First, it's incredibly distant. Its orbit takes
• 7:34
  it from about 2 .7 to 4 .6 billion miles from
• 7:39
  the Sun. One trip around the Sun takes 248 Earth
• 7:44
  years, which means Pluto has not even completed
• 7:47
  a full orbit since the day it was discovered.
• 7:52
  Its orbit is also tilted and elongated. unlike
• 7:55
  the nearly circular paths of the major planets.
• 7:59
  Sometimes Pluto actually comes closer to the
• 8:02
  Sun than Neptune. That happened from 1979 to
• 8:06
  1999. Despite that overlap, the two worlds never
• 8:11
  collide because Pluto is locked in a three -to
• 8:14
  -two orbital resonance with Neptune. Pluto is
• 8:19
  also tiny. It's just 2 ,377 kilometers across.
• 8:25
  making it smaller than Earth's moon. Its surface
• 8:28
  is made of exotic ices, nitrogen, methane, and
• 8:32
  water ice, existing at temperatures around minus
• 8:35
  375 degrees Fahrenheit or colder. For much of
• 8:46
  the 20th century, astronomers assumed Pluto was
• 8:50
  probably a cold, inactive world. a lonely outpost
• 8:54
  at the edge of the solar system. But then another
• 8:57
  discovery complicated the story. In 1978, astronomer
• 9:03
  James Christie noticed something strange while
• 9:06
  studying telescope images of Pluto. The planet
• 9:09
  appeared slightly elongated, almost as if there
• 9:12
  were a bump sticking out of one side. At first,
• 9:16
  he assumed it was an error in the image, but
• 9:19
  the bump kept appearing. and its position kept
• 9:22
  changing. Christie realized what he was seeing.
• 9:26
  Pluto had a moon. The moon was named Charon after
• 9:31
  the fairy man of the dead in Greek mythology
• 9:34
  who carried souls across the river Styx to Pluto's
• 9:38
  realm. Charon turned out to be enormous relative
• 9:42
  to Pluto, about half of Pluto's diameter. So
• 9:46
  large, in fact, that the two worlds orbit a point
• 9:49
  in space between them rather than Charon simply
• 9:52
  circling Pluto. In some ways, Pluto and Charon
• 9:56
  are better described as a binary planetary system,
• 10:00
  and later observations revealed even more companions.
• 10:04
  Four smaller moons named Nix, Hydra, Kerberos,
• 10:08
  and Styx. But by this point, astronomers were
• 10:12
  beginning to notice something else, something
• 10:15
  that would eventually lead to Pluto's downfall.
• 10:22
  Beginning in the 1990s, astronomers discovered
• 10:25
  hundreds of icy bodies beyond Neptune. This region
• 10:30
  became known as the Kuiper Belt, and suddenly
• 10:33
  Pluto didn't look so unique anymore. It looked
• 10:37
  like one member of a much larger population of
• 10:40
  distant icy worlds. Then in 2005, astronomers
• 10:44
  discovered an object called Eris, roughly comparable
• 10:48
  in size to Pluto. And that forced a very uncomfortable
• 10:52
  question. If Pluto is a planet, should Eris be
• 10:55
  a planet too? And if Eris is a planet, how many
• 10:59
  more planets might we find out there? Dozens,
• 11:02
  hundreds, maybe more. In 2006, the International
• 11:06
  Astronomical Union convened a meeting in Prague
• 11:09
  to settle the issue. Astronomers debated a deceptively
• 11:14
  simple question. What is a planet? After deliberation,
• 11:18
  a new definition was adopted. To qualify as a
• 11:22
  planet, a body must orbit the sun, it must be
• 11:25
  round due to its own gravity, and it must clear
• 11:29
  its orbital neighborhood of other objects. Pluto
• 11:34
  failed that last requirement. It shares its region
• 11:37
  of space with many Kuiper Belt objects. And so
• 11:41
  the verdict came down. Pluto was no longer part
• 11:45
  of the starting lineup. It was reclassified as
• 11:48
  a dwarf planet. And many astronomers supported
• 11:52
  the decision. Among the most visible voices explaining
• 11:57
  the change to the public was astrophysicist Neil
• 12:00
  deGrasse Tyson. who had already removed Pluto
• 12:04
  from the planetary lineup at the Hayden Planetarium
• 12:07
  years earlier. But the astronomer who calls himself
• 12:11
  the real Pluto killer is Mike Brown of Caltech.
• 12:16
  Brown had spent years surveying the outer solar
• 12:19
  system and was convinced that Pluto was not a
• 12:22
  unique planet but simply a member of a much bigger
• 12:25
  population of icy bodies beyond Neptune. As his
• 12:30
  team began discovering more and more large Kuiper
• 12:33
  Belt objects, Brown openly argued that astronomers
• 12:37
  would eventually have to face a choice. Either
• 12:40
  accept dozens of new planets, or rethink Pluto's
• 12:44
  status entirely. After 76 years of glory, Pluto
• 12:49
  was demoted from being considered one of nine
• 12:51
  planets in our solar system to just a dwarf planet.
• 12:55
  And the scientists who made the discovery will
• 12:56
  always be known as the man who killed Pluto.
• 13:00
  Pluto's not a planet because it's part of this
• 13:02
  vast swarm of bodies out beyond Neptune in what
• 13:05
  we now call the Kuiper belt. There are thousands,
• 13:08
  millions of objects out there of which Pluto
• 13:10
  is only the second most massive. Mike Brown,
• 13:14
  a professor at Caltech, says he We will never
• 13:16
  hear the end of it. Mostly it was adults thinking
• 13:19
  of their childhood memory that were upset. Brown's
• 13:24
  discoveries were what truly pushed the debate
• 13:27
  to its breaking point. But for many Pluto fans,
• 13:30
  Tyson became the public face of the decision.
• 13:33
  Here he is chatting with Stephen Colbert about
• 13:36
  being an accessory to the ruling. discovered
• 13:44
  the objects in the outer solar system that forced
• 13:46
  that vote. In fact, he's guilty. In fact, his
• 13:49
  Twitter handle is called Pluto Killer. He admits
• 13:53
  it. Who is this Mike Brown you're throwing under
• 13:56
  the bus right now? Under the space bus. He put
• 13:59
  himself under the bus. I'm pointing it out. But
• 14:01
  here's the thing is that now some of your buddies
• 14:03
  at NASA want to reinstate Pluto as a planet because
• 14:08
  they want the designation of planet to be closer
• 14:10
  to people's intuition rather than some arbitrary
• 14:14
  scientific designation. Okay. They should just
• 14:17
  like get over it. OK. Why do you think people
• 14:21
  want to name it a planet? Pluto had it coming
• 14:23
  from the beginning. It was never really belong.
• 14:27
  Pluto's orbit crosses that of another planet.
• 14:30
  That's no kind of behavior for a planet. No!
• 14:34
  You got to stay in your lane. Stay in your lane!
• 14:36
  Stay in your lane! All right, OK. No! Clyde Tombaugh
• 14:41
  passed away in 1997, but his connection to Pluto
• 14:46
  didn't end there. When NASA launched the spacecraft
• 14:52
  New Horizons in 2006, the very same year Pluto
• 14:56
  was demoted, a small portion of Tom Bow's ashes
• 15:00
  was placed aboard the spacecraft. Nine years
• 15:04
  later, that spacecraft arrived at Pluto, symbolically
• 15:08
  carrying its discoverer to the world he had found.
• 15:12
  Few scientists in history have ever traveled,
• 15:14
  at least in spirit, to visit their own discovery.
• 15:24
  When New Horizons flew past Pluto on July the
• 15:28
  14th 2015, the images it sent back stunned the
• 15:32
  world. Pluto was not a frozen relic. It had towering
• 15:37
  mountains made of water ice, vast glaciers of
• 15:40
  frozen nitrogen, a thin blue atmosphere, and
• 15:44
  a giant heart -shaped plane. Pluto even has a
• 15:49
  strange seasonal atmosphere made mostly of nitrogen.
• 15:53
  As the dwarf planet moves farther from the Sun,
• 15:56
  that atmosphere can actually freeze and fall
• 15:59
  back to the surface like frost. Some scientists
• 16:03
  even think Pluto may hide a subsurface ocean
• 16:06
  beneath its icy crust. Against all expectations,
• 16:11
  Pluto appeared geologically active, dynamic,
• 16:14
  and alive with strange processes scientists are
• 16:18
  still trying to understand. For a world barely
• 16:21
  half the size of Earth's moon, it turned out
• 16:24
  to be astonishingly complex. And for some, that
• 16:28
  meant Pluto is a planet. You could really undercut
• 16:32
  all the planets. They're all dwarf planets because
• 16:35
  there isn't a planet that clears its entire orbit
• 16:37
  around the sun. That's former NASA Administrator
• 16:40
  Jim Bridenstine. I think the way you should define
• 16:43
  a planet... is based on its intrinsic values,
• 16:46
  not the values that constantly change like orbital
• 16:49
  dynamics. So when I think about Pluto and what
• 16:52
  we got back from New Horizons, here's what we
• 16:54
  know. Pluto has an ocean under its surface. Pluto
• 17:01
  has complex organic compounds on its surface.
• 17:06
  Pluto has a multi -layer atmosphere and Pluto
• 17:09
  has its own moons. I'm here to tell you, as the
• 17:12
  NASA administrator, I believe Pluto is a planet.
• 17:20
  Today, the verdict of 2006 still stands. Pluto
• 17:24
  remains officially classified as a dwarf planet.
• 17:29
  Every February, hundreds of people travel to
• 17:32
  northern Arizona to celebrate Pluto at the place
• 17:35
  where it was discovered, the historic Lowell
• 17:38
  Observatory. The event is called the I Heart
• 17:41
  Pluto Festival, and it's part science conference,
• 17:45
  part community celebration, and part love letter
• 17:49
  to the distant world. Visitors attend astronomy
• 17:53
  lectures, telescope demonstrations, and talks
• 17:56
  from planetary scientists. There are art exhibits,
• 17:59
  science presentations, and even a pub crawl through
• 18:03
  downtown Flagstaff, where astronomers give short
• 18:06
  talks about Pluto between stops. the man who
• 18:23
  discovered Pluto. Well the events that Lowell
• 18:26
  Observatory and Flagstaff have put on are always
• 18:28
  very important to us. We very much appreciate
• 18:31
  the honors that they have been given to my father
• 18:34
  and to his accomplishments here at Lowell Observatory
• 18:37
  and in Flagstaff. It may sound like an unusual
• 18:40
  festival but it speaks to something deeper. Pluto's
• 18:44
  discovery in 1930 was one of the great moments
• 18:47
  in American astronomy. and the city of Flagstaff
• 18:51
  still takes pride in being the place where a
• 18:54
  faint speck of light first revealed a new world.
• 18:58
  Pluto was the only planet discovered in the United
• 19:00
  States, and Americans love an underdog. Pluto
• 19:05
  being the smallest planet certainly fits the
• 19:08
  bill. If there's one lesson here, it's this.
• 19:16
  Pluto was never the end of the solar system.
• 19:19
  It's the first visible member of an entire neighborhood
• 19:22
  we hadn't discovered yet. That neighborhood is
• 19:25
  the Kuiper Belt, a vast disk of icy leftovers
• 19:29
  from the era when the planets were forming about
• 19:32
  four and a half billion years ago. The Belt begins
• 19:36
  just beyond Neptune, roughly 30 astronomical
• 19:39
  units from the Sun, and extends outward at least
• 19:43
  a 50 AU and maybe further. Pluto is the first
• 19:48
  house on the street leading out into the suburbs
• 19:51
  of our solar system. The front porch of the Kuiper
• 19:55
  Belt, perhaps. The real mystery is how many more
• 19:59
  worlds are still waiting to be found. And that
• 20:02
  makes Pluto less like a fallen planet, and more
• 20:05
  like the cosmic welcome sign to an undiscovered
• 20:09
  country. After a quick break, I'll tell you what
• 20:31
  you can expect to see in this week's night sky.
• 20:34
  Stay with us. Welcome back. Now that we've closed
• 20:50
  the case file on Pluto, let's turn our attention
• 20:53
  to the sky above us this week. Mid -March is
• 20:56
  a beautiful time for backyard astronomers. Winter's
• 21:00
  constellations are slowly slipping westward.
• 21:03
  The first hints of spring are rising in the east,
• 21:06
  and the night sky itself feels like it's in the
• 21:09
  middle of a seasonal handoff. So if you're stepping
• 21:12
  outside this week, here's what you can expect
• 21:15
  to find. We'll begin with the moon. It's moving
• 21:18
  through its waning crescent phase during most
• 21:21
  of this week. You'll see it rising in the early
• 21:23
  morning hours, appearing as a delicate, curved
• 21:26
  sliver before sunrise. The new moon arrives at
• 21:30
  week's end, leading to inky dark skies suitable
• 21:34
  for deep sky observation. And March the 20th
• 21:38
  brings another milestone. That's the vernal equinox,
• 21:41
  the official beginning of spring in the Northern
• 21:44
  Hemisphere. On this day, the Sun crosses the
• 21:47
  celestial equator and day and night become nearly
• 21:51
  equal in length. Astronomically speaking, it
• 21:54
  also means the night sky is beginning its seasonal
• 21:57
  transformation. Winter constellations like Orion
• 22:01
  and Taurus are drifting westward, while the stars
• 22:04
  of spring begin climbing into the eastern sky.
• 22:08
  If you live somewhere with reasonably dark skies,
• 22:11
  this week offers a wonderful opportunity to spot
• 22:14
  something many observers have never seen before,
• 22:17
  the zodiacal light. About 20 minutes after sunset,
• 22:21
  look toward the western horizon. Under dark conditions,
• 22:25
  you may notice a faint triangular glow rising
• 22:28
  upward along the path of the planets. This ghostly
• 22:33
  pillar of light is sunlight reflecting off millions
• 22:36
  of tiny dust particles that fill the inner solar
• 22:39
  system, leftovers from comet tails and asteroid
• 22:43
  collisions. March is one of the best times of
• 22:46
  year to see it because the angle of the solar
• 22:48
  system's plane is steep against the evening horizon
• 22:52
  near the spring equinox. If you've never seen
• 22:55
  it before, it looks almost like a faint, tilted
• 22:58
  beam of twilight reaching up into the stars.
• 23:02
  This week also offers several planets to explore.
• 23:06
  First up is Jupiter, which remains one of the
• 23:09
  brightest objects in the night sky this month.
• 23:11
  It shines prominently in the constellation Gemini,
• 23:15
  easily visible in the evening and remaining high
• 23:17
  in the sky for much of the night. If you step
• 23:20
  outside after sunset, Jupiter will likely be
• 23:23
  the first planet your eye catches. Its brightness
• 23:26
  is startling. Low in the western sky, you may
• 23:30
  still catch Venus in the evening twilight, though
• 23:33
  it sets fairly quickly. Saturn has been slipping
• 23:37
  towards the Sun's glare and is becoming difficult
• 23:40
  to observe now, lingering very low near the horizon
• 23:43
  shortly after sunset. With binoculars or a telescope,
• 23:47
  you can also try tracking down Uranus, which
• 23:50
  sits in the constellation Taurus, not far from
• 23:53
  the famous Pleiades star cluster. Through binoculars,
• 23:57
  Uranus appears as a tiny aquamarine star among
• 24:01
  the surrounding field. Meanwhile, the stars of
• 24:05
  spring are rising in the east. Look for the constellation
• 24:08
  Leo, which contains the bright star Regulus,
• 24:11
  marking the heart of the celestial lion. LEO
• 24:15
  is home to one of the most rewarding regions
• 24:18
  of the sky for telescope observers. The LEO triplet
• 24:22
  features a small group of galaxies M65, M66,
• 24:27
  and NGC 3628. Under dark skies, even modest scopes
• 24:33
  can reveal these three distant islands floating
• 24:36
  together in space, 35 million light -years away.
• 24:40
  If you're feeling adventurous, try hunting down
• 24:43
  one of the sky's most unusual deep sky objects.
• 24:48
  The Eskimo Nebula, also known as NGC 2392, sits
• 24:53
  in the constellation Gemini, not far from Jupiter.
• 24:57
  This object is a planetary nebula, a glowing
• 25:01
  shell of gas expelled by a dying star. Through
• 25:05
  a telescope it appears as a small bluish disk,
• 25:08
  and with larger instruments, observers often
• 25:11
  notice a fuzzy halo that gives it the appearance
• 25:14
  of a face framed by a parka hood, hence the nickname
• 25:18
  the Eskimo Nebula. And somewhere far beyond the
• 25:22
  reach of backyard telescopes, Pluto continues
• 25:25
  its slow journey around the Sun. We actually
• 25:29
  discussed how to view Pluto back in episode 64.
• 25:33
  So, if you have access to a massive telescope,
• 25:36
  a camera, and some very dark skies, go for it!
• 25:44
  That's going to do it for this week. If you found
• 25:47
  this episode interesting, please share it with
• 25:49
  a friend who might enjoy it. The easiest way
• 25:52
  to do that is by sending folks to our website,
• 25:55
  StarTrails .Show. And, if you'd like to support
• 25:59
  the show, use the link on the site to buy me
• 26:01
  a coffee. That really helps. Be sure to follow
• 26:05
  Star Trails on Blue Sky and YouTube. Links are
• 26:09
  in the show notes. Until we meet again beneath
• 26:11
  the stars, clear skies everyone.