It is surrounded by much brighter lights — even the distant Pluto could be about 10,000 times brighter — and so scientists have to be sure that they point telescopes at exactly the right point and pick out an already very unlikely speck of light.
That’s why the scientists have spotted the potential planet by seeing the disturbances that it is causing in the gravitational field of the far star system. There appears to be a “great perturber” upsetting the movement of other objects in that far away region, and the new paper — authored by Michael Brown and Konstantin Batygin and published in the Astronomical Journal — claims that is being caused by a mysterious, unknown world.
The solar system doesn’t often change. The only recent addition was Pluto, which was found in 1930 and spent most of the 21st century as its most distant and smallest planet — until it was controversially downgraded to being just a dwarf planet, and the solar system went back to having eight members.
If the new planet is real, then it will definitely be a planet, scientists say. Since it dominates a bigger region than any of the other planets, it would “the most planet-y of the planets in the whole solar system”, Brown said.
The downgrading of Pluto was partly the result of work by astronomer Michael Brown, who co-wrote the new paper. He had found that Pluto was surrounded by a huge number of similarly-sized planets, and the International Astronomical Union decided that Pluto would be excluded from a new definition.
The two astronomers found the new potential planet while they were looking at those small rocks. They seemed to fly around on orbits that couldn’t be happening by chance, and instead were best explained by a big ninth planet sitting out there with them.
A ninth planet has long been hypothesised — and become the basis of some conspiracy theories — originally going under the name Planet X. It was first talked about more than a century ago, and looking for that planet was what brought astronomers to find Pluto.