Is it Planet Nine or a massive disc?
There’s another suggestion for what’s causing some unusual orbital architecture.
So, are those mystery orbits in outermost reaches of solar system caused by an unknown ninth planet? There’s another group of astronomers suggesting the answer is “no”.
They believe it can all be explained by the combined gravitational force of small objects orbiting the sun beyond Neptune.
“The Planet Nine hypothesis is a fascinating one, but if the hypothesised ninth planet exists, it has so far avoided detection,” says Antranik Sefilian, from the University of Cambridge in the UK.
In a paper published in The Astronomical Journal, Sefilian and colleagues suggest there’s a disc made up of small icy bodies with a combined mass as much as 10 times that of Earth. When combined with a simplified model of the solar system, the gravitational forces of the disc can account for the unusual orbital architecture exhibited by some objects at the outer reaches of the solar system.
Theirs is not, they concede, the first theory involving such a disc, but it is the first, they say, which explains the significant features of the observed orbits while accounting for the mass and gravity of the other eight planets in our solar system.