Last year, two astronomers were studying the most distant objects orbiting the sun that we have found in all time, when they suddenly saw something interesting. These ultra-long Kuiper belt objects, instead of having randomly oriented orbits, seem to be stretched out and tilted in a certain direction. If one or two objects did this, it could be written off as an accident. But there were six of them. The chances of this being an accident were about 0.0001%. Instead, astronomers Konstantin Batygin and Mike Brown proposed a radically new theory: somewhere there is a distant ninth planet, more massive than Earth, but smaller than Uranus and Neptune. It is she who moves all these objects. 16 months have passed since then, and this is what we have in fact.
First, the idea is great. Every time you try to come up with an explanation, apart from this idea, nothing seems particularly convincing. But like many brilliant ideas, it is also possible that it is simply wrong. Seeing six ultra-distant objects doing something out of the ordinary does not mean that there are not six million such objects, we just do not see them. Perhaps this is normal behavior.
Astronomers call this bias: in any dataset, you only look at the objects that are easiest to see / find / measure, and these objects will tend to be outstanding in nature. If you look over the tall grass and only see giant elephants, you might conclude that elephants do not exist, that is your prejudice. But there is a way to get rid of it: ask what happens if you collect new additional data, better and more accurate. What specific predictions can be made to confirm or disprove your theory? In the case of the ninth planet, there will be five.
1. If the ninth planet is real, it should spawn more distant objects with this strange unexpected alignment. If an ultra-long-range massive planet existed in the outer solar system, it would sometimes have to gravitationally collide with other objects in the Kuiper belt. Some will collide with the planet, some will be thrown out of the solar system, some will be thrown into orbit in the opposite direction to the ninth planet. We can verify this if we find more objects with large maximum orbital distances from the Sun: hundreds of times more distant from the Sun than the Earth.
2. The orbits of these objects should be inclined in the same direction as the original six. An unusual systematic shift for six objects has a chance of about 1 in 1000. If you find a dozen more objects with a similar tilt, the chance will be one in a billion. Finding more objects and measuring their displacement is a great indirect test of the ninth planet hypothesis.
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3. A small group of objects, contrary to prediction # 1, will have orbits offset in the same direction as the ninth planet. Such a prediction was made by Batygin and Brown in their second work on this topic, and there is an interesting grain in it, because such objects have never been found yet.
4. The orbital planes of these objects should be inclined in the same direction with a small spread. This is a refinement of prediction # 2, determining the distribution of systematic biases. Additional simulations conducted by Brown's team and presented at a conference in October showed where the “north pole” of the orbital planes of these objects should be. If a large number of these very long Kuiper belt objects are discovered, their distributions can be compared with those predicted.
5. More importantly, the ninth planet must be there and can be found from the ground. If there is a large, massive planet out there, it must reflect enough sunlight so that it can be captured even from the ground, even with our modern telescopes.
As far as circumstantial evidence goes, the idea of a ninth planet is pretty good. Predictions 1 through 4 are circumstantial, and since the existence of planet 9 was first predicted, four more objects have been found: one by the OSSOS team and three by the Sheppard and Trujillo team. A green object orbit to the right is the first example of prediction # 3, which is interesting. But it will be even more interesting if we arrange all the detected objects according to the modeling of their orbital planes. They will match Brown's models!
The more circumstantial evidence appears, the more you want to see matches, given the limited data available. But there are drawbacks here:
All this data is not without bias; we found objects that come relatively close to the sun.
The total number of detected objects - ten - is too small to be considered significant.
The uncertainty of predictions # 3 and # 4 blurs the significance of the findings.
With all this, the ninth planet remains elusive.
But there is hope.
The complete dataset allows us to impose stricter restrictions on the location of the ninth planet, and the most likely scenarios place it in the constellation Taurus. As we approach the June solstice, this constellation becomes more visible, which means that the coming months will be the best for the search for the ninth planet. The search will be undertaken by both amateur astronomers and professionals. Mike Brown also has his own blog on the current state of the search for planet nine; despite wild optimism, he is very restrained in his statements.
The most surprising results of Kepler's mission were that the vast majority of the planets in the Universe turned out to be not small, solid worlds like Earth or Mars, not big gas giant worlds like Neptune or Jupiter, but super-Earths, that is, something in between. Since this discovery became known to the world, astronomers have asked themselves: why is there not a single such world in our solar system? If the hypothesis of the ninth planet is correct, then such a world exists, and now is the best time to search for it.
ILYA KHEL