Something like that?

Yeah.

Maybe nine out, Pushing 99% probability.

This is wishful thinking.

I mean, if you're that sure, find it in the farthest reaches of our solar system way past Neptune and Pluto's and Ninth Planet may be lurking.

It's predicted to have amassed five times that of earth into orbit once every 10,000 years on a highly elliptical inclined orbit.

So why do some scientists suspect that such a strange object exists?

That's what I've come to Caltech to find out.

We're going to do your work.

You know, my I usually do it wherever.

Wherever I have a couple of minutes of free time.

I just So this is where a lot of it against my name is Constantine Tegan.

I am a professor of planetary science at Caltech, and I do all kinds of astrophysics seen planetary studies, including stuff about planet night.

These are variable transformations.

I'll tell you where the planet nine boundary lives.

It's like that everything to the left of that is all night.

So I'm here to find out about hidden planets and how to find hidden planets with math.

Okay, so how do we do that?

I mean, do you want to start at the beginning of this sort of endeavor or or do you want to jump into Planet nine?

Where do you want to start?

Well, that's actually let's start at the beginning, because the beginning is ah, a long and beautiful history to it in its origins.

Date back to 17.

81 I believe when Uranus was first discovered by Herschel and when Herschel discovered Uranus, he immediately realized that the star that was slowly moving across the sky had actually been imaged many, many times before.

There was a matter of going back to old observations of kind of retracing the orbit that Uranus was following us on the sky.

And astronomers and mathematicians of the time immediately noticed that there was a problem with the orbit of this newly discovered planet.

It was deviating from where it was supposed to be, but a a French mathematician, by the name of or bombed a very A Eventually did this beautiful and very complicated set of calculations that said Okay, if there is a planet, is there right in that part of the sky.

Then we can explain the anomalous motion of Uranus.

And when once there was a mathematical prediction of where to look, astronomers were then able to discover Neptune with basically pinpoint accuracy.

House quickly did they find Neptune?

So this is a remarkable story.

They found Neptune in one night because they knew exactly where to look.

There could be 1/9 planet.

There's there's a lot of space for 1/9 planet in the outer solar system, but there's no good evidence for 1/9 planet at the present time.

Particularly scary thing about the ninth Planet is that a lot of people want to believe that there's a nice planet.

And we all know this is huge psychological bias to the effect that if you want to believe something is true, you will find evidence, real or not, that it's true.

Everyone and their brother in the last 170 years have predicted planets beyond Neptune.

But all of these theories have failed.

Today I think that we meeting myself and my collaborator slash partner in crime, Mike Brown, are right.

Our understanding of the solar system has evolved dramatically in the last 20 years, we've discovered that there exists this one additional belt of icy debris called the Keiper Belt.

Renzi's a kind of big I see asteroids that are maybe the size of L A floating around beyond that tune.

Who's responsible for finding the caper belt I found the capable with with Ted Lieu way.

We're looking for anything actually beyond the orbit of Saturn.

So the puzzle in 1985.

The puzzle waas Why is it that the inner part of the solar system is full of asteroids and comets and also kinds of things planets, all this stuff?

But then, when you go beyond Saturn, there's Uranus, Neptune on this plateau, and then that's it.

Why would the outer solar system be so empty?

It's a very simple question of the kind that I could understand.

Theo Answer was, Well, let's have a look.

You know, maybe it's not really empty.

Maybe it ISS, in which case that would be interesting, but maybe it's not.

So we started a survey to find stuff beyond Saturn, and we did the survey for a long time, five years or something.

Six years on, found actually nothing for that whole time, including nothing just beyond.

Saturn will be expected to find stuff until finally, in 1992.

We've got this thing way out and we could tell immediately its way out.

45 58 years from the slow motion across this guy.

We found this thing out there.

What?

We call him out.

First identified.

Copperbelt object is actually the second because Pluta was misidentified back in 1930 for all sorts of reasons connected with sociology and propaganda and things like that.

People wanted to find a planet.

And so no matter what, proof must be a planet.

So that process is continued.

We have more than 2000 of these objects now.

So in 25 years, 2000 of these things have been found.

We think the population is vast.

There's a 1,000,000,000 things bigger than a kilometre across.

Maybe more, maybe a couple of 1,000,000,000.

It's some of the more distant objects that appear to some people to show this orbital alignment.

They have in particular very large perihelion distance.

So he never come close to the sun.

They never come close to even let you.

If you look at the most distant objects in this belt of debris called the Kuiper Belt.

All of their orbits kind of point into the same direction.

Is it possible that there are some going in the other direction?

We just haven't found them there.

Yeah, ofcourse.

That's a great question.

Generically, when you search for objects in the night sky, they're always would have called observational biases.

You're always limited to finding objects on Lee where you look.

So this is a key question that you have to ask, right?

Is it that we only found objects that are all pointing that way?

They're orb is pointing that way because we only look there.

The answer is that there is a chance that this is this is all a false alarm, okay.

And that chance is one in 500.

There are bodies that occasionally will swing out into other directions.

It's more that overall, if you look at it, there is an overall tendency.

So here what we see is a pretty typical kind of simulation of the type.

That way do we start the solar system in an initial come totally random state where all the objects are pointing everywhere for scale these pink circles here are Uranus and Neptune and this long ellipse, this long pink ellipses planet nine, these blue guys, these blue orbits are long period Keiper belt objects, the ones that in the real solar system we see the clustering among.

And these gold or greenish ellipses are the more short period, more proximate members of the Kuiper Belt, which are not clustered at all.

So it takes a long time.

But about two billion years into the evolution of the solar system, you begin to see the fact that objects that Air Colin ear with Planet nine have all been scattered away, removed from the solar system dynamically and the old kind of remaining members of the distant solar system on the objects that point the opposite way again, it's a remarkable gravitational signature.

Gravitational.

One way sign, if you will, That something is confining these orbits, keeping them clustered and pulling them all into the same plane.

You know the experts, I think Scott Shepard on chatter.

He'll first noticed this alignment.

They call it a 2.6 sigma result, which means that you know, it doesn't really meet the threshold for acceptance.

The scientific would you be looking at five Sigma?

Is that I mean, the standard thing is three signal right, but half of all three signal results are wrong.

It's what I always as an observer.

So the more significance, the better.

But 2.6 is not enough.

So even though these clusters of asteroid orbits in the Kuiper Belt provide the best evidence for Planet nine, there's a chance that further Kiper belt observations will find different, Uncluttered orbits.

But regardless, there are two other solar system mysteries that could be explained by the existence of Planet Nine.

These properties of Planet nine, they seem like kind of nuts, like a period of 10,000 years.

That's not like any of the planets that we have found.

So why would we have such a strange planet hanging out up there?

Yeah, great question.

Indeed.

None of this is reminiscent of anything solar system.

Right?

If you for a second, ignore the period, right and ask yourself about mass massive five earth masses.

We don't have anything in the solar system.

That's five earth masses.

We go from 1 to 17 when we go from Earth to Neptune isn't wild, actually, turns out this is the most common type of planet in the galaxy that we have discovered around other stars, and it may be reversed.

The fact that the solar system doesn't host a object, which is five earth masses come closer to the sun is actually kind of weird indeed.

Five Earth Masses Turns out It's kind of standard outcome of planet formation, their arm or wild things out there now.

And this is really my favorite aspect of the planet.

Nine hypothesis is the fact that Planet nine actively flips orbits on their side.

You should not expect to find objects in the solar system.

That air flipped on their side, andare orbiting the sun perpendicular to the planets.

And you should definitely not expect objects that air orbiting the solar system the wrong way.

Yet we find them, they exist in the Kuiper Belt, and this has actually been a problem since before Planet nine was even a thought.

Planet nine has this intriguing mode of dynamical evolution that it instills upon distant orbits where it takes them and at the expense of kind of circular rising these distant objects by making their orbits less elliptical flips them upside down and then makes them more elliptical again.

It's a complicated, dynamical evolution and really at a detailed level.

You have to go to the computer simulations to understand how it works.

But the key kind of product of planet of the existence of Planet nine is the expectation that such objects will exist.

And we see them.

Really.

There isn't another kind of natural mechanism to generate these highly inclined bodies.

You know you have the plane of most of the bodies, and then some of the bodies out there apparently have their orbits almost tilted up to 90 degrees.

Is that just weird, or is that stronger evidence for?

That's one of the things that they claim to explain with the planet nine hypothesis, and that's a good thing in favor of the hypothesis.

But again, you know, you need to find the planet to be sure what's going on in the region that we have not yet been able to probe because we can't see faint enough.

We don't know, way don't know.

So when do you think we're gonna find Planet Nine?

That's a great question.

Um, so observing the sky has proven to be an extreme challenge.

The search for Planet nine is extremely, extremely difficult.

It's just kind of dim enough at the outer parts of its orbit, where it can be discovered with current telescopes.

But you but everything has to go right by.

Everything has to go, right?

No, Moon.

The atmosphere has to be calm so that the light is not messed up by turbulence.

Such nights do come around every year, but they don't come around very often.

So it Since 2017 we've had exactly two successful runs, right?

Successful observational runs where we had sort of a string of nights where we could take pictures of the same part of the sky over and over again.

S so we're about 20% maybe a little bit more now, 25% done with survey that we're carrying out to search for Planet nine.

If things go at this rate, it might take about a decade.

I think the commencement of the L s s T telescope, which is coming on line 2022 23.

That's gonna help a lot because that's going to first of all, discover many more of these objects and we'll be able to refine the theoretical model better and also just by direct observation.

It'll rule out.

Or it'll either find Planet nine to rule out a big chunk of its orbit.

So we could kind of zero in that way a lot more.

So it's a It's an interpretive process, I would guess to mate decade or less So, Volumetric Lee.

We've discovered most of the solar system in the last 25 years.

Something like that.

What do you mean volumetric?

I mean that the volume of the region occupied by the planets is very small.

It's 10,000 cubic astronomical units.

But as you go further out, you know, the volume of that spear that encapsulates all the objects that we've been able to observe is just going up dramatically.

So if you go 10 times further out, which will now just about able to do you increase the volume that you're looking at by a factor of 1000 the whole bunch of stuff going on, you know, solar system is to me an unknown place.

We fool ourselves to thinking that we know everything about it just because we've only been looking close and we have a lot of data from spacecraft and so on.

But the further away you go, the less known it is, and the more mysterious it is on this ninth Planet.

Thing is part of that.

Because essentially, when you go far enough away from the sun, there's enough room to hide almost anything you want.

It would be so faint you could put almost anything big planets, small planets, whatever you want.

We would not have seen it yet.

If you know when you do find it, who gets to name it?

That's something we don't think about.

You have a name in the back of your head?

Um, the only David Bowie.

Yeah, there was.

There's a online petition on change dot or to name planning.

Nine.