The search for our solar system's ninth planet
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0:01 - 0:04I'm going to tell you a story
from 200 years ago. -
0:05 - 0:08In 1820, French astronomer Alexis Bouvard
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0:08 - 0:13almost became the second person
in human history to discover a planet. -
0:13 - 0:17He'd been tracking the position
of Uranus across the night sky -
0:17 - 0:18using old star catalogs,
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0:18 - 0:21and it didn't quite go around the Sun
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0:21 - 0:23the way that his predictions
said it should. -
0:23 - 0:25Sometimes it was a little too fast,
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0:25 - 0:27sometimes a little too slow.
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0:27 - 0:31Bouvard knew that
his predictions were perfect. -
0:31 - 0:34So it had to be that those
old star catalogs were bad. -
0:34 - 0:36He told astronomers of the day,
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0:36 - 0:39"Do better measurements."
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0:39 - 0:40So they did.
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0:40 - 0:42Astronomers spent the next two decades
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0:42 - 0:46meticulously tracking the position
of Uranus across the sky, -
0:46 - 0:50but it still didn't fit
Bouvard's predictions. -
0:50 - 0:52By 1840, it had become obvious.
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0:52 - 0:55The problem was not
with those old star catalogs, -
0:55 - 0:58the problem was with the predictions.
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0:58 - 1:00And astronomers knew why.
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1:00 - 1:04They realized that there must be
a distant, giant planet -
1:04 - 1:05just beyond the orbit of Uranus
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1:05 - 1:07that was tugging along at that orbit,
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1:07 - 1:10sometimes pulling it along a bit too fast,
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1:10 - 1:12sometimes holding it back.
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1:13 - 1:15Must have been frustrating back in 1840
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1:15 - 1:18to see these gravitational effects
of this distant, giant planet -
1:18 - 1:22but not yet know how to actually find it.
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1:22 - 1:24Trust me, it's really frustrating.
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1:24 - 1:26(Laughter)
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1:26 - 1:28But in 1846, another French astronomer,
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1:28 - 1:29Urbain Le Verrier,
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1:29 - 1:30worked through the math
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1:30 - 1:33and figured out how to predict
the location of the planet. -
1:33 - 1:36He sent his prediction
to the Berlin observatory, -
1:36 - 1:38they opened up their telescope
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1:38 - 1:41and in the very first night
they found this faint point of light -
1:41 - 1:43slowly moving across the sky
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1:43 - 1:44and discovered Neptune.
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1:44 - 1:48It was this close on the sky
to Le Verrier's predicted location. -
1:50 - 1:54The story of prediction
and discrepancy and new theory -
1:54 - 1:57and triumphant discoveries is so classic
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1:58 - 2:00and Le Verrier became so famous from it,
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2:00 - 2:03that people tried to get in
on the act right away. -
2:03 - 2:06In the last 163 years,
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2:06 - 2:11dozens of astronomers have used
some sort of alleged orbital discrepancy -
2:11 - 2:15to predict the existence
of some new planet in the solar system. -
2:16 - 2:19They have always been wrong.
-
2:20 - 2:22The most famous
of these erroneous predictions -
2:22 - 2:24came from Percival Lowell,
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2:24 - 2:29who was convinced that there must be
a planet just beyond Uranus and Neptune, -
2:29 - 2:31messing with those orbits.
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2:31 - 2:33And so when Pluto was discovered in 1930
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2:33 - 2:35at the Lowell Observatory,
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2:35 - 2:39everybody assumed that it must be
the planet that Lowell had predicted. -
2:39 - 2:42They were wrong.
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2:42 - 2:46It turns out, Uranus and Neptune
are exactly where they're supposed to be. -
2:46 - 2:47It took 100 years,
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2:47 - 2:49but Bouvard was eventually right.
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2:49 - 2:53Astronomers needed to do
better measurements. -
2:53 - 2:55And when they did,
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2:55 - 2:58those better measurements
had turned out that -
2:58 - 3:03there is no planet just beyond
the orbit of Uranus and Neptune -
3:03 - 3:06and Pluto is thousands of times too small
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3:06 - 3:08to have any effect on those orbits at all.
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3:08 - 3:12So even though Pluto
turned out not to be the planet -
3:12 - 3:13it was originally thought to be,
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3:14 - 3:17it was the first discovery
of what is now known to be -
3:17 - 3:22thousands of tiny, icy objects
in orbit beyond the planets. -
3:22 - 3:25Here you can see the orbits of Jupiter,
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3:25 - 3:27Saturn, Uranus and Neptune,
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3:27 - 3:30and in that little circle
in the very center is the Earth -
3:30 - 3:33and the Sun and almost everything
that you know and love. -
3:33 - 3:35And those yellow circles at the edge
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3:35 - 3:38are these icy bodies
out beyond the planets. -
3:38 - 3:40These icy bodies are pushed and pulled
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3:40 - 3:42by the gravitational fields of the planets
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3:42 - 3:45in entirely predictable ways.
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3:45 - 3:50Everything goes around the Sun
exactly the way it is supposed to. -
3:51 - 3:52Almost.
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3:52 - 3:54So in 2003,
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3:54 - 3:56I discovered what was at the time
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3:56 - 4:00the most distant known object
in the entire solar system. -
4:00 - 4:02It's hard not to look
at that lonely body out there -
4:02 - 4:05and say, oh yeah, sure,
so Lowell was wrong, -
4:05 - 4:06there was no planet just beyond Neptune,
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4:06 - 4:09but this, this could be a new planet.
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4:09 - 4:11The real question we had was,
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4:11 - 4:13what kind of orbit
does it have around the Sun? -
4:13 - 4:15Does it go in a circle around the Sun
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4:15 - 4:16like a planet should?
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4:16 - 4:20Or is it just a typical member
of this icy belt of bodies -
4:20 - 4:24that got a little bit tossed outward
and it's now on its way back in? -
4:24 - 4:27This is precisely the question
-
4:27 - 4:32the astronomers were trying
to answer about Uranus 200 years ago. -
4:32 - 4:35They did it by using
overlooked observations of Uranus -
4:35 - 4:38from 91 years before its discovery
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4:38 - 4:40to figure out its entire orbit.
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4:40 - 4:42We couldn't go quite that far back,
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4:42 - 4:46but we did find observations
of our object from 13 years earlier -
4:46 - 4:49that allowed us to figure out
how it went around the Sun. -
4:49 - 4:50So the question is,
-
4:50 - 4:53is it in a circular orbit
around the Sun, like a planet, -
4:53 - 4:54or is it on its way back in,
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4:54 - 4:56like one of these typical icy bodies?
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4:56 - 4:58And the answer is
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4:58 - 4:59no.
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4:59 - 5:02It has a massively elongated orbit
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5:02 - 5:06that takes 10,000 years
to go around the Sun. -
5:06 - 5:08We named this object Sedna
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5:08 - 5:10after the Inuit goddess of the sea,
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5:10 - 5:14in honor of the cold, icy places
where it spends all of its time. -
5:14 - 5:16We now know that Sedna,
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5:16 - 5:17it's about a third the size of Pluto
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5:17 - 5:20and it's a relatively typical member
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5:20 - 5:22of those icy bodies out beyond Neptune.
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5:22 - 5:26Relatively typical,
except for this bizarre orbit. -
5:26 - 5:28You might look at this orbit and say,
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5:28 - 5:31"Yeah, that's bizarre,
10,000 years to go around the Sun," -
5:31 - 5:33but that's not really the bizarre part.
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5:33 - 5:35The bizarre part is
that in those 10,000 years, -
5:35 - 5:39Sedna never comes close
to anything else in the solar system. -
5:39 - 5:41Even at its closest approach to the Sun,
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5:41 - 5:44Sedna is further from Neptune
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5:44 - 5:46than Neptune is from the Earth.
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5:47 - 5:49If Sedna had had an orbit like this,
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5:49 - 5:52that kisses the orbit of Neptune
once around the Sun, -
5:52 - 5:55that would have actually been
really easy to explain. -
5:55 - 5:57That would have just been an object
-
5:57 - 5:59that had been in
a circular orbit around the Sun -
5:59 - 6:00in that region of icy bodies,
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6:00 - 6:03had gotten a little bit
too close to Neptune one time, -
6:03 - 6:06and then got slingshot out
and is now on its way back in. -
6:07 - 6:12But Sedna never comes close
to anything known in the solar system -
6:12 - 6:14that could have given it that slingshot.
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6:14 - 6:17Neptune can't be responsible,
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6:17 - 6:20but something had to be responsible.
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6:20 - 6:23This was the first time since 1845
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6:23 - 6:28that we saw the gravitational effects
of something in the outer solar system -
6:28 - 6:29and didn't know what it was.
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6:30 - 6:33I actually thought I knew
what the answer was. -
6:33 - 6:37Sure, it could have been
some distant, giant planet -
6:37 - 6:38in the outer solar system,
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6:38 - 6:41but by this time,
that idea was so ridiculous -
6:41 - 6:43and had been so thoroughly discredited
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6:43 - 6:45that I didn't take it very seriously.
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6:45 - 6:46But 4.5 billion years ago,
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6:46 - 6:51when the Sun formed in a cocoon
of hundreds of other stars, -
6:51 - 6:52any one of those stars
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6:52 - 6:55could have gotten
just a little bit too close to Sedna -
6:55 - 6:59and perturbed it onto the orbit
that it has today. -
6:59 - 7:03When that cluster of stars
dissipated into the galaxy, -
7:03 - 7:06the orbit of Sedna would have been
left as a fossil record -
7:06 - 7:09of this earliest history of the Sun.
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7:09 - 7:11I was so excited by this idea,
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7:11 - 7:12by the idea that we could look
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7:12 - 7:14at the fossil history
of the birth of the Sun, -
7:14 - 7:16that I spent the next decade
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7:16 - 7:19looking for more objects
with orbits like Sedna. -
7:19 - 7:22In that ten-year period, I found zero.
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7:22 - 7:23(Laughter)
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7:23 - 7:27But my colleagues, Chad Trujillo
and Scott Sheppard, did a better job, -
7:27 - 7:30and they have now found several objects
with orbits like Sedna, -
7:30 - 7:32which is super exciting.
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7:32 - 7:33But what's even more interesting
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7:33 - 7:36is that they found that all these objects
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7:36 - 7:40are not only on these distant,
elongated orbits, -
7:40 - 7:45they also share a common value
of this obscure orbital parameter -
7:45 - 7:49that in celestial mechanics we call
argument of perihelion. -
7:50 - 7:53When they realized it was clustered
in argument of perihelion, -
7:53 - 7:55they immediately jumped up and down,
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7:55 - 7:58saying it must be caused
by a distant, giant planet out there, -
7:58 - 8:01which is really exciting,
except it makes no sense at all. -
8:01 - 8:04Let me try to explain it
to you why with an analogy. -
8:04 - 8:07Imagine a person walking down a plaza
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8:07 - 8:10and looking 45 degrees to his right side.
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8:11 - 8:13There's a lot of reasons
that might happen, -
8:13 - 8:15it's super easy to explain, no big deal.
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8:15 - 8:17Imagine now many different people,
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8:17 - 8:21all walking in different
directions across the plaza, -
8:21 - 8:24but all looking 45 degrees
to the direction that they're moving. -
8:24 - 8:26Everybody's moving
in different directions, -
8:26 - 8:28everybody's looking
in different directions, -
8:28 - 8:32but they're all looking 45 degrees
to the direction of motion. -
8:32 - 8:34What could cause something like that?
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8:35 - 8:36I have no idea.
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8:36 - 8:40It's very difficult to think of any reason
that that would happen. -
8:40 - 8:41(Laughter)
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8:41 - 8:44And this is essentially
what that clustering -
8:44 - 8:48in argument of perihelion was telling us.
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8:48 - 8:51Scientists were generally baffled
and they assumed it must just be a fluke -
8:51 - 8:53and some bad observations.
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8:53 - 8:54They told the astronomers,
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8:54 - 8:57"Do better measurements."
-
8:57 - 9:00I actually took a very careful look
at those measurements, though, -
9:00 - 9:01and they were right.
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9:01 - 9:03These objects really did all share
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9:03 - 9:06a common value of argument of perihelion,
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9:06 - 9:07and they shouldn't.
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9:07 - 9:09Something had to be causing that.
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9:11 - 9:15The final piece of the puzzle
came into place in 2016, -
9:15 - 9:18when my colleague, Konstantin Batygin,
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9:18 - 9:21who works three doors down from me, and I
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9:21 - 9:23realized that the reason
that everybody was baffled -
9:23 - 9:28was because argument of perihelion
was only part of the story. -
9:28 - 9:30If you look at these
objects the right way, -
9:30 - 9:34they are all actually lined up
in space in the same direction, -
9:34 - 9:38and they're all tilted in space
in the same direction. -
9:38 - 9:42It's as if all those people on the plaza
are all walking in the same direction -
9:42 - 9:46and they're all looking
45 degrees to the right side. -
9:46 - 9:47That's easy to explain.
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9:47 - 9:50They're all looking at something.
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9:50 - 9:54These objects in the outer solar system
are all reacting to something. -
9:55 - 9:57But what?
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9:57 - 10:00Konstantin and I spent a year
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10:00 - 10:05trying to come up with any explanation
other than a distant, giant planet -
10:05 - 10:06in the outer solar system.
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10:06 - 10:11We did not want to be the 33rd and 34th
people in history to propose this planet -
10:11 - 10:14to yet again be told we were wrong.
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10:15 - 10:17But after a year,
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10:17 - 10:18there was really no choice.
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10:18 - 10:20We could come up with no other explanation
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10:20 - 10:23other than that there is a distant,
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10:23 - 10:26massive planet on an elongated orbit,
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10:26 - 10:28inclined to the rest of the solar system,
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10:28 - 10:31that is forcing these patterns
for these objects -
10:31 - 10:33in the outer solar system.
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10:33 - 10:35Guess what else a planet like this does.
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10:35 - 10:37Remember that strange orbit of Sedna,
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10:37 - 10:40how it was kind of pulled away
from the Sun in one direction? -
10:40 - 10:44A planet like this would make
orbits like that all day long. -
10:44 - 10:46We knew we were onto something.
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10:46 - 10:49So this brings us to today.
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10:49 - 10:53We are basically 1845, Paris.
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10:53 - 10:54(Laughter)
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10:54 - 11:00We see the gravitational effects
of a distant, giant planet, -
11:00 - 11:02and we are trying to work out
the calculations -
11:02 - 11:05to tell us where to look,
to point our telescopes, -
11:05 - 11:06to find this planet.
-
11:06 - 11:09We've done massive suites
of computer simulations, -
11:09 - 11:11massive months of analytic calculations
-
11:11 - 11:14and here's what I can tell you so far.
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11:14 - 11:17First, this planet,
which we call Planet Nine, -
11:17 - 11:20because that's what it is,
-
11:21 - 11:24Planet Nine is six times
the mass of the Earth. -
11:24 - 11:26This is no slightly-smaller-than-Pluto,
-
11:26 - 11:29let's-all-argue-about-
whether-it's-a-planet-or-not thing. -
11:29 - 11:32This is the fifth largest planet
in our entire solar system. -
11:32 - 11:36For context, let me show you
the sizes of the planets. -
11:36 - 11:40In the back there,
you can the massive Jupiter and Saturn. -
11:40 - 11:43Next to them, a little bit smaller,
Uranus and Neptune. -
11:43 - 11:46Up in the corner, the terrestrial planets,
Mercury, Venus, Earth and Mars. -
11:46 - 11:48You can even see that belt
-
11:48 - 11:51of icy bodies beyond Neptune,
of which Pluto is a member, -
11:51 - 11:53good luck figuring out which one it is.
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11:53 - 11:55And here is Planet Nine.
-
11:57 - 11:59Planet Nine is big.
-
11:59 - 12:00Planet Nine is so big,
-
12:00 - 12:03you should probably wonder
why haven't we found it yet. -
12:03 - 12:04Well, Planet Nine is big,
-
12:04 - 12:06but it's also really, really far away.
-
12:06 - 12:11It's something like
15 times further away than Neptune. -
12:11 - 12:14And that makes it about 50,000 times
fainter than Neptune. -
12:14 - 12:17And also, the sky is a really big place.
-
12:17 - 12:19We've narrowed down where we think it is
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12:20 - 12:22to a relatively small area of the sky,
-
12:22 - 12:24but it would still take us years
-
12:24 - 12:26to systematically cover
the area of the sky -
12:26 - 12:28with the large telescopes that we need
-
12:28 - 12:32to see something that's
this far away and this faint. -
12:32 - 12:35Luckily, we might not have to.
-
12:35 - 12:40Just like Bouvard used
unrecognized observations of Uranus -
12:40 - 12:42from 91 years before its discovery,
-
12:42 - 12:46I bet that there are unrecognized images
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12:46 - 12:49that show the location of Planet Nine.
-
12:50 - 12:53It's going to be a massive
computational undertaking -
12:53 - 12:55to go through all of the old data
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12:55 - 12:58and pick out that one faint moving planet.
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12:59 - 13:01But we're underway.
-
13:01 - 13:03And I think we're getting close.
-
13:03 - 13:06So I would say, get ready.
-
13:06 - 13:10We are not going to match Le Verrier's
-
13:10 - 13:11"make a prediction,
-
13:11 - 13:13have the planet found in a single night
-
13:13 - 13:15that close to where
you predicted it" record. -
13:15 - 13:19But I do bet that within
the next couple of years -
13:19 - 13:21some astronomer somewhere
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13:21 - 13:24will find a faint point of light,
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13:24 - 13:26slowly moving across the sky
-
13:26 - 13:29and triumphantly announce
the discovery of a new, -
13:29 - 13:32and quite possibly not the last,
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13:32 - 13:34real planet of our solar system.
-
13:34 - 13:35Thank you.
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13:35 - 13:39(Applause)
- Title:
- The search for our solar system's ninth planet
- Speaker:
- Mike Brown
- Description:
-
Could the strange orbits of small, distant objects in our solar system lead us to a big discovery? Planetary astronomer Mike Brown proposes the existence of a new, giant planet lurking in the far reaches of our solar system -- and shows us how traces of its presence might already be staring us in the face.
- Video Language:
- English
- Team:
- closed TED
- Project:
- TEDTalks
- Duration:
- 13:52
Erin Gregory edited English subtitles for The search for our solar system's ninth planet | ||
Erin Gregory approved English subtitles for The search for our solar system's ninth planet | ||
Erin Gregory edited English subtitles for The search for our solar system's ninth planet | ||
Joanna Pietrulewicz accepted English subtitles for The search for our solar system's ninth planet | ||
Joanna Pietrulewicz edited English subtitles for The search for our solar system's ninth planet | ||
Joanna Pietrulewicz edited English subtitles for The search for our solar system's ninth planet | ||
Ivana Korom edited English subtitles for The search for our solar system's ninth planet | ||
Ivana Korom edited English subtitles for The search for our solar system's ninth planet |