Astronomers believe there is a giant
planet lurking in the outer solar system, and we're going to learn more about it
starting right now. Welcome back to Launch Pad, I'm Christian
Ready, your friendly neighborhood astronomer. In 2016, astronomers Mike
Brown and Konstantin Batygin at Caltech announced evidence of a giant planet in
the distant outer solar system. In this video, I'd like to tell you about how
they arrived at this claim and where we stand on the hunt for Planet 9. Now
claims of new planets in our solar system are nothing new. In 1906, Percival
Lowell believed that there was a giant planet that was disturbing the orbits of
Uranus and Neptune. Lowell calculated that the planet must be at least the mass of
Jupiter but perhaps even larger. He spent the last decade of his life searching
for Planet X to no avail. When Clyde Tombaugh discovered Pluto in 1930, people
thought that Lowell's giant planet was found. But Pluto wasn't a giant. In fact it's
not even a Mercury sized planet. Pluto turned out to be a member of a new
region of trans-Neptunian objects called the Kuiper belt. As for Lowell's calculations,
well, it turns out he was wrong. He used the wrong values for the masses of Neptune
and Uranus, and when Voyager 2 flew past both planets in the 1980s, their masses
were precisely calculated and the perturbances of the other orbits
that Lowell discovered went away. Still that didn't stop astronomers from
invoking Planet X on 573 different occasions,
only to find that claim disproven on every single attempt. So why are
astronomers so convinced that there is a new planet out there? In order to
understand that, we need to go back to 2003 when Mike Brown and his colleagues
discovered Sedna. It's a 1000 kilometer-wide dwarf planet
that orbits far beyond Neptune. But Sedna's orbit isn't just far, it's shaped
differently than anything that had been discovered before.
Sedna has a close approach to the Sun - or perihelion - of 76 astronomical units, and
swings out to an aphelion of 934 astronomical units. This highly
eccentric orbit was unlike anything that we'd had ever discovered in the solar
system before, and astronomers immediately wanted to know just what
Sedna was doing out there on such a strange orbit. In 2014 Chad Trujillo and
Scott Sheppard discovered that a new object, 2012 VP 113, was also on a really
eccentric orbit that was not unlike Sedna's. Both of these objects are so
distant that they are completely oblivious to the gravity of the inner
planets. In other words, they're detached from the rest of the solar system. Soon
additional objects were discovered that are a little closer to the Kuiper belt,
but are otherwise on very eccentric orbits like the Sednoids.
But there was something else really peculiar about these objects: not only
were their orbits eccentric but they were all pointing in roughly the same
direction. Mike Brown and Konstantin Batygin analyzed these orbits and they
discovered that not only were they aligned but they were also inclined by
roughly the same amount with respect to the rest of the solar system. In fact
they even calculated that the chances of these alignments occurring by random
chance were something like 0.007%. they concluded
that something must be shepherding the orbits of these objects. And that
something turns out to be a giant planet about 10 times Earth's mass on a 10,000
to 20,000 year orbit around the Sun. They dubbed this new world "Planet 9". But they
also realized something else: over time Planet 9 could twist up the orbits of
inner Kuiper belt objects and fling them into highly eccentric perpendicular
orbits to the rest of the solar system. Sure enough, a population of exactly
those types of objects on exactly those types of orbits were discovered year prior. And
Planet 9 explained something else that has puzzled astronomers for a very long
time about our solar system: all of the planets orbit the Sun and roughly the
same plane, inclined by about degree of each other. But the Sun is
tilted by about six degrees, and that's a significant shift from the plane of the
planets. But Planet 9's orbit is highly inclined with respect to the solar
system. That means that Planet nine can act as a kind of a lever arm, and
gradually tilt the orbits of the planets. In other words, it's not the Sun that's
tilted but the orbits of the planets themselves that have been tilted,
courtesy of Planet nine. And Planet nine gives our solar system something that we
didn't even realize we were missing until relatively recently. 2000 planetary
systems have been discovered so far with planets ranging in size from smaller
than Mars to larger than Jupiter. But the most common type of planet found to
date ranges in size between Earth and Neptune. These are called "Super Earths",
and we don't seem to have anything like that in our solar system. But now with
Planet 9 we do! Planet 9 is estimated to be about 10 times Earth's mass which
would put it firmly in the super-Earth category. But why would our super-Earth
be so far away from the rest of the other planets? It turns out that if you
simulate the early solar system with four giant cores, you end up with the
four giant planets that you have today. But if you simulate five giant cores
forming in the early solar system, the least massive of these cores gets
ejected while the remaining four cores goes on to form the four giant planets.
The ejected core's growth is stunted and it only grows to about ten Earth masses.
So Planet 9 explains so much about our solar system. It explains the
orbital clustering of distant outer bodies. It explains the apparent tilt of
the Sun. It even gives our solar system its very own super-Earth. Only one teeny
little problem is that we haven't actually found Planet 9 yet. But
astronomers are looking for it, and the good news is that they're pretty sure it
should be found somewhere near the constellation Orion. The bad news is that
it's still an enormous chunk of the sky to have to search through, so astronomers
have formed teams in a friendly competition to see who can find planet
nine first. And in October 2018, Scott Sheppard and Chad Trujillo
announced that a new object in the outer solar system has an orbit that fits
perfectly into the Planet 9 model. This object is called 2015 TG387, and
because it was discovered near Halloween and because of "TG" in its name, it's been
nicknamed "The Goblin". The Goblin is tiny, only 300 kilometers across and is most
likely a frozen chunk of ammonia and methane ice. The Goblin's orbit is the
largest and most eccentric of any object of its kind ever discovered. Its
perihelion is "only" 65 au, so it does come in a little bit closer than Sedna. But it
swings out to an aphelion of, get this, 2,300 au, making this the most distant
object of its type ever discovered. And best of all, The Goblin's orbit is exactly
where it would be expected to be if it were being shepherded by Planet 9. And it
gets even better because astronomers have found another set of objects in
orbits that are anti-aligned with the previous orbits, but they would fit
perfectly inside of Planet 9's predicted orbit, allowing it to be held
stable by the giant planet. Now all this makes for some compelling evidence that
there is a distant giant planet lurking in the outer solar system, and we're
going to learn how astronomers are searching for Planet 9 in our next video.
So make sure that you subscribe, and ring that notification bell so that you don't
miss out when our next video is posted. Until next time keep watching the skies.
If there was any actual evidence The New York planetarium would've stuck a ninth planet back in their exhibit. They don't care how many there are, they're not going to lose their job if its nine or eight or ten or forty. They just care that when a kid asks to see the data that proves the existence of all this stuff, then they can give that kid the data. And data comes in huge tables of numbers, stuff you can use to double check reality by making predictions about where stuff will be tomorrow and looking to see if its where you predicted based on the data you calculated it from.
I guess this is the follow up video:
https://www.youtube.com/watch?v=1nVOnX2eABw
I think "goblin" might be turned into a spaceship.
https://gizmodo.com/discovery-of-goblin-solar-system-object-bolsters-the-ca-1829459509