Are there a ninth major planet in the outer reaches of our solar system? This question has become one of the most intensely discussed planetary sciences. The idea of a large, unknown planet Nine, which is so far from the sun that it has not yet been discovered, is certainly tempting. So far there was evidence of its existence, but still no confirmation. But we could be closer to finding it. Last week, an international team of researchers submitted further evidence that was detailed in a new study, suggesting that Planet Nine influences the behavior of a strange object – 2015 BP519 (aka Caju) – in the outer solar system.
Astronomers at Caltech had previously calculated the probable existence of a large ninth planet (sorry, Pluto) in the outer edges of the solar system, based on the orbits of smaller icy objects. Their orbits were disturbed by the gravitational influence of … something.
According to the calculations of the astronomers, the previously undiscovered planet should be about four times the size of the earth and ten times its size. That would make it look like Super Earth exoplanets orbiting other stars. And that would be interesting, as many super-Earths were discovered now, though they were not seen in our own solar system. But maybe there is one, so far from the sun, that he has remained hidden.
Such a discovery would be very exciting because super-Earths are larger than the Earth, but smaller than Uranus or Neptune, unlike anything else in our solar system. If a big Planet Nine is there, it's very far, much further than Pluto. If it does exist, it will probably take 10,000 to 20,000 years for orbit around the sun to complete.
Astronomers first discovered before 2015 BP519 (Caju) 2015. It is a trans Neptune object (TNO), which are generally smaller planets orbiting the Sun beyond the Neptune orbit. Caju is one of only a dozen or so known objects categorized as extreme trans Neptune objects (ETNOs). Such objects have a larger half-axis than 150 astronomical units (AU) and a perihelion closest to the Sun – more than 30 AU. Caiu's estimated diameter is 248-434 miles (400-700 km), making it a potential dwarf planet. So it's a very interesting object.
Since its discovery, further analysis has shown that Caju has an unusual orbit nearly perpendicular to all known planets. In fact, Caju has the highest propensity of TNO that has been discovered so far.
Surprisingly, exactly one such object was predicted by computer models performed by the team looking for Planet Nine. Caltech astronomer Mike Brown, who was not part of the new study, but is active in research from Planet Nine, told PopSci.com on May 22, 2018:
I'm pretty excited about the new object. It is the predicted link between the very distant elongated orbits we know about and the much closer orbits we've seen.
So Caju adds a growing amount of evidence to the elusive planet Nine, which, if really there, is still out of sight of astronomers. Astronomer Konstantin Batygin, the first to name, size and distance Brown Planet Nine, told Space.com on May 21 that as of October 2017, at least five lines of evidence pointed to the existence of Planet Nine. Earlier, in 2017, astronomers had found evidence that 22 other TNOs seemed to have disturbed their orbits by another large invisible planet. Batygin said:
If you remove this explanation and imagine that Planet Nine does not exist, you will create more problems than you solve. Suddenly you have five different puzzles, and you have to develop five different theories to explain them.
Conclusion: While Planet Nine has still not been confirmed, there is growing evidence that perhaps an unseen planet is actually the bleak outer edges of our solar system.
Source: Discovery and dynamic analysis of an extreme trans-Neptunian object with high orbital tilt