I didn't make that name up.
But, notice it, too, has that same characteristic.
At the time of the discovery the astronomers who discovered it said,
this must mean there's a planet out there.
But, I remind you from about 1847 onward astronomers had been saying,
there's a planet out there once every several months.
Every time anything slightly unusual was found in the outer solar system,
astronomers would jump to the conclusion that there must be a planet.
My colleague Konstantin Batygin, who has an office right down the hall, and
I started looking and realized something that we thought was pretty astounding.
If you look at all of the most distant objects in the solar system, and
Sedna in there, I think that's Sedna right there, in fact.
And VP112 is probably that one.
But, you look at all the rest of these.
They're all swept off in this direction in an astounding way.
After working on this for a year, we became convinced that
the only explanation was there actually has to be a distant and
massive planet in orbit around the sun, on a very eccentric orbit.
A very eccentric orbit, we thought, probably went something like this, and
essentially herded these little Kuiper Belt objects into place.
To test that idea we tried out computer simulations.
In these computer simulations you can see, you can't see because it's covered up.
The sun is right here in the middle.
Planet is on this orbit out here like this, and all of these other blue points
are Kuiper Belt objects that we initially start randomly strewing around the sky.
We let them interact gravitationally with this planet for
four billion years and we see what happened.
Now, and what happens?
Well, the first thing you notice is that the planet very
quickly clears out many of the objects that were nearby it.
There are many fewer objects in the Kuiper Belt now,
in this extended Kuiper Belt, than there were to begin with.
What are we looking for?
Well, we're looking to see if it captures objects into orbits that are like this.
That's what we want to see.
And the answer, well, I'll give you the preview.
The answer is it never does.
Our initial hypothesis on how a planet might actually do this was wrong.
What's it doing?
Well, lets watch very carefully and objects are going to get captured
onto these orbits, these anti-aligned orbits with the giant planets.
There they are.
We're almost at three and a half billion years now,
and this is starting to look a lot like the solar system that we see now.
Over time it finally clears out, and finally clears out.
And at four billion years,
we really are left with something that looks a little bit familiar.
So, let's go back to those objects in the Kuiper Belt that we've seen.
If Kuiper Belt objects are going to be swept off in this direction by a planet,
that planet is pointing in the opposite direction.
What's interesting is I didn't show you this before, but
if you look at those Kuiper Belt objects they're all actually tilted
compared to the plane of the solar system too.
And that shows us that that planet,
which we now call Planet Nine must also be likewise tilted.
So is it true?
Is it really out there?
In the time since we first proposed this we have found more and
more evidence of different things from the solar system that are being perturbed by
this massive planet out there.
I would say, the probability that it's
not true is much lower than the probability that it is true.
If there is no planet out there, there are so many things that need to be explained
in the outer solar system that we currently have no explanation for.
Now, people have been saying this since 1847.
So, it sounds a little bit crazy to sit here and say,
well, everybody has been wrong for 170 years, but we're right.
But, I do have something I'd like to say, which is that everybody had been wrong for
170 years.
But we're right.
Let me show you what this planet looks like.
Okay, we don't actually know what it looks like.
But we know how massive it is.
The reason we know how massive it is, is because we do those computer simulations
and we put in a less massive and a more massive planet.
And we make the one that fits the best.
And the answer is, it has to be something like 10 times the mass of the earth.
It puts it between Earth which, is one times the mass of the Earth.
And Neptune or Uranus, which are 15-17 times the mass of the Earth.