Does Planet 9 Exist?

So do you think Planet 9

exist

s with 99.8% probability? Something like that. Yeah, maybe 99... I'll turn it up more. 99.9% probability. This is an illusion. It is. I mean, if you're so sure, find it. In the farthest reaches of our solar system, far beyond Neptune and Pluto, a ninth

planet

may be lurking. It is predicted to have a mass five times that of Earth and will orbit once every 10,000 years in a highly elliptical and inclined orbit. So why do some scientists suspect that such a strange object

exist

s? That's what I've come to Caltech to find out. Where do you like to do your work?

You know I usually do it anywhere I have a couple minutes of free time, I just do it. So this is where a lot of this is done. My name is Konstantin Batygin. I'm a professor of

planet

ary science at Caltech and I do all kinds of astrophysics, planetary studies, including things about planet 9. These are variable transformations. I will tell you where the limit of planet 9 is. It is like this. So everything to the left of that is all of planet 9. So I'm here to learn about hidden planets and how to find hidden planets with math. Good.

So how do we do that? I mean, do you want to start from the beginning of this kind of Do you try hard or do you want to jump to planet 9? Where do you want to start? Well, actually let's start at the beginning because the beginning has a long and beautiful history. And its origins date back to 1781, I believe. When Herschel first discovered Uranus and when Herschel discovered Uranus, he immediately realized that the star that was moving slowly across the sky had actually been photographed many times before and it was a matter of going back to old observations and retracing the orbit that Uranus followed in the sky and astronomers and mathematicians of the time noticed it immediately. 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 French mathematician named Urbain Le Verrier finally did this beautiful, very complicated set of calculations that said, "Okay, there's a planet there, right, in that part?" of the sky, then we can explain the anomalous movement of Uranus. And when, once there was a mathematical prediction of where to look, astronomers were able to discover Neptune with basically millimeter precision, how 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 a ninth planet.

There is plenty of room for a ninth planet in the outer solar system, but there is no hard evidence that a ninth planet exists at this time, and one particularly scary thing about the ninth planet is that many people want to believe that a ninth planet exists. and we all know that there is a huge psychological bias that if you want to believe something is true, you will find evidence, real or not, that it is true. Everyone and their brother in the last 170 years has predicted planets beyond Neptune. but all these theories have not worked to date.

I think we, meaning my collaborator/partner in crime Mike Brown and I, are right. Our understanding of the solar system has evolved dramatically over the past 20 years. We've discovered that there is this additional belt of icy debris called the Kuiper belt. These are large icy asteroids perhaps the size of Los Angeles and floating past Neptune. Who is responsible for finding the Kuiper belt? I found the Kuiper belt with my student Jane Luu. We were looking for something beyond the orbit of Saturn, so the puzzle, in 1985, the puzzle was why the inner part of the solar system is full of asteroids and comets and that kind of thing, planets, all these things, but then , when you go beyond Saturn, there is Uranus, there is Neptune, there is Pluto and that's it.

Why would the outer solar system be so empty? It's a very simple question that I can understand and the answer was well, let's take a look! You know, maybe it's not really empty, maybe it is, in which case it would be interesting, but maybe it's not. So we started a study to find things beyond Saturn and we did it for a long time, five years or something, six years and, in fact, we found nothing during that whole time, including nothing beyond Saturn, where we expected to find things until finally in 1992 we got this and could immediately tell it was 45 or 50 au from the slow motion across the sky we discovered. there, what we now call the first identified Kuiper Belt object is actually the second, because Pluto was misidentified in 1930 for all kinds of reasons related to sociology and propaganda and things like that.

People wanted to find a planet, and so whatever happens Pluto must be a planet for that process to continue. We have over 2,000 of these objects now, so in 25 years 2,000 of these things have been found. We think the population is huge, there are a billion things over a kilometer in diameter, maybe more. Maybe a couple billion are some of the most distant objects that some people seem to show this orbital alignment, and in particular they have a very large perihelion distance, so they never get close to the Sun, they never get close or not even Neptune. The most distant objects in this debris belt called the Kuiper Belt all have their orbits pointing in the same direction.

Is it possible that there are some going in the other direction and we just haven't found them? They are there. Yes of course. That's a great question. Generally, when you look for objects in the night sky, there are always what are called observation biases. So, you're always limited to finding objects only where you look, so this is a key question to ask, right? that we only find objects that point in that direction, right, their orbits point in that direction because we only look there? The answer is that there is a possibility that this is a false alarm, okay? and that probability is one in 500.

There are bodies that will occasionally move in other directions; If you look at it, there's a general trend, so what we see here is a pretty typical type of simulation of the type that we see. Do we start the solar system in some sort of totally random initial state where all objects point everywhere to determine scale? These pink circles here are Uranus and Neptune and this long ellipse, this long pink ellipse is planet nine, these blue guys, these blue orbits. are long-period Kuiper Belt objects that we see clustering together in the real solar system, and these gold or greenish ellipses are the closest, shorter-period members of the Kuiper Belt that aren't clustered at all, so it takes a long time. , but approximately two billion years into the evolution of the solar system we begin to see the fact that objects that are collinear with planet nine have all been dispersed, dynamically removed from the solar system and are the only type of members remaining of the distant solar system. system the objects that point in the opposite direction.

Again, it's a remarkable gravitational signature, a one-way gravitational signal, if you will, that something is confining these orbits, keeping them bunched together and bringing them all closer to the same plane, you know, the experts, me. Think Scott Shepard and Chad Raheel, who first noticed this lineup. They call it two point six sigma or result, which means that, you know, it

does

n't actually meet the acceptance threshold. The scientific... Would you be looking at five sigma? ? Is that... I mean the standard is three sigma, right? but half of the 3 sigma results are wrong, is what I always say as an observer, so the more significant the better, but two point six is ​​not enough, although these groups of asteroid orbits in the Kuiper belt provide the best evidence of the existence of the Planet. 9, there is a possibility that future Kuiper Belt observations will find different, clear orbits.

But regardless there are two other mysteries of the solar system that could be explained by the existence of Planet Nine. These properties of Planet Nine, it seems kind of crazy like a period of ten thousand years, that's not like any of the planets we've found. So why would we have such a strange planet out there? Yes, great question. In fact, none of this is reminiscent of anything in the solar system, right? If for a second you ignore the point and wonder about the mass. Mass of five land masses. We don't have anything in the solar system that has five Earth masses.

We go from one to 17, when we go from Earth to Neptune. Is it wild? Actually, it turns out that this is the most common type of planet in the galaxy that we have discovered around other stars. It may be the other way around: that the fact that the solar system

does

not host an object that has five Earth masses is closer to the Sun. In fact, it turns out that five Earth masses is a standard result of plant formation. There are more wild things out there. Oh, and this is actually my favorite aspect of the Planet Nine hypothesis.

It is the fact that Planet 9 is active. reverse their orbits on their sides, you shouldn't expect to find objects in the solar system that are turned on their sides and are orbiting the Sun perpendicular to the planets and you definitely shouldn't expect objects that are orbiting the solar system in the wrong direction, so talk Sin However, we found them. Good? They exist in the Kuiper Belt and this has actually been a problem since before Planet 9 was even a thought. Planet Nine has this intriguing mode of dynamic evolution that it instills in distant orbits where it takes them and, at the cost of circularizing them. distant objects by making their orbits less elliptical, flips them over, and then makes them more elliptical again.

It's a complicated dynamic evolution and really, at a detailed level, you have to go to computer simulations to understand how it works, but the key kind of product of the existence of Planet 9 is the expectation that such objects existed, and we see them . and I think there really is no other type of natural mechanism to generate these highly tilted bodies. You know you have the plane of most of the bodies, and then some of the bodies that are there apparently have their orbits almost tilted up to 90°. degrees is that just strange, or is it stronger evidence of... that's one of the things they claim to explain with the planet 9 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 of what is happening in the region that we have not yet been able to probe, because we cannot see faintly enough.

We do not know. Yes. We don't know. So when do you think we'll find Planet 9? That's a great question. So observing the sky has proven to be extremely challenging. The search for planet 9 is extremely difficult. It's dark enough in the outer parts of its orbit where it can be discovered with current telescopes, but you, but everything. It has to go well and by everything it has to go well I mean that there is no moon, the atmosphere has to be calm so that the light is not affected by turbulence. Those nights happen every year, but they don't happen very often.

So since 2017 we have had exactly two successful races. Well, successful observing runs where we had sort of a series of nights where we were able to take pictures of the same part of the sky over and over again, so we're about 20% done, maybe a little more now, 25% with the survey that We are carrying out the search for planet 9, if things go at this pace, it could take about a decade. I think that the start of the LSST telescope, which will come into operation in 2022,23, that will help a lot because, first of all, Discover many more of these objects and we will be able to better refine the theoretical model and, in addition, with only direct observation you will find the planet 9 or it will discard a large part of its orbit so we can get to zero that way. much more.

So it's an iterative process. I would estimate a decade or less. So volumetrically we've discovered most of the solar system in the last 25 years, something like that. What do you mean by volumetrically? I mean that the volume of the region occupied by the planets is very small, it is 10,000 cubic astronomical units, but as you get further away, you know that the volume of that sphere that encapsulates all the objects that we have been able to observe, is simply going up dramatically. , so if you go ten times as far, which we can almost do now, you increase the volume you're seeing by a factor of a thousand.

There's a lot going on, you know? The solar system is, for me, an unknown place. You know, we fool ourselves into thinking we know everything about him. Just because we've just been looking closely and we have a lot of data from spacecraft and stuff, but the farther away you go, the less known it is and the more mysterious it is and this ninth planet is part of that, because essentially, when you get far enough away from the Sun , there is enough space to hide almost anything you want, it will be so weak that you can put almost anything.

Planetsbig ones, small planets, whatever you want. We wouldn't have seen it yet. If you find him, who can name him? Oh, that's something we don't think or talk about. Don't you have a name in the back of your head? The... Just David Bowie. Yeah, there's an online petition on change.org to name Planet Nine David Bowie, and at first I thought it was a bit silly, but then there's all this David Bowie-type mythology you could create, if it has moons you could have Ziggy Stardust, Starman, and all these things So, you know, I thought, I'm not serious, but it would also be something extraordinary if we had Jupiter, Saturn, Uranus, Neptune, and David Bowie.