There are eight known planets in the solar system (since Pluto was excluded from the list of planets), but some time ago there was evidence that there may be another planet. This "Ninth Planet" (aka Planet-X or Nibiru) is hiding at the outer edge of our solar system. Until now, it has not been possible to find it, but a new study has made it possible to determine where it should be located.
The proof of the existence of planet 9 is its gravitational attraction to other bodies. If a planet exists, then its gravity will affect the orbits of other planets. So if something seems to be pulling the planet, just do some math to find the source. This is how Neptune was discovered when John Couch Adams and Urbain Le Verrier independently noticed that Uranus seemed to be attracted by an invisible planet.
In the case of Planet 9, we have no gravitational effect on the planet. What we see, however, is a strange cluster of small icy bodies in the outer solar system known as Kuiper Belt Objects (KBOs). If there were no planets behind the Kuiper belt, one would expect that the orbits of the OPK objects would be randomly oriented within the orbital plane of the solar system. But instead, we see that many of the orbits of the OPK objects are grouped in the same orientation. It is possible that this is just an accident, but it is unlikely.
Back in 2016, the authors looked at the statistical distribution of the MIC and concluded that clustering is caused by an undetected outer planet. According to their calculations, this world has a mass of 5 Earth's and is located about 10 times farther from the Sun than Neptune. The authors even calculated a wide area of the sky where the planet could be. But the search yielded nothing. This has led some to conclude that the planet does not exist. The strangeness of the orbit does not prove the existence of the planet. Ask the planet Vulcan. Others have argued that planet 9 exists, but we cannot see it because it is an ancient black hole.
This new study revisits the original work in light of the criticism it received. One of the main criticisms is that the outer bodies of the solar system are difficult to find, so we look for them where it is convenient. The clustering effect that we are observing can be simply caused by biased data. Taking into account the observational error, the authors found that clustering is still statistically unusual. The probability that this is an accident is only 0.4%. When they recalculated the likely orbit of Planet 9, they were able to better determine where to look.
One of the interesting aspects of the study is that in the new calculated orbit, Planet 9 is closer to the Sun than originally thought. This is strange, because if she was closer, then we should have found her already. The authors argue that observations to date have ruled out the closest options for Planet 9, which helps further narrow its possible location. If the planet exists, it should be discovered by Vera Rubin Observatory in the near future.
This study is inconclusive, and many astronomers still claim that Planet 9 does not exist. But this study makes it clear that we won't have to argue about it for a long time. Either it will be discovered in the near future, or observations will exclude it as an explanation for the effect of clustering of the DIC.
Research: Michael E. Brown, Konstantin Batygin."Orbit of the Ninth Planet". ArXiv Preprint: 2108.09868 (2021).