A huge planet containing 10 times the mbad of Earth could explain the unusual orbit of a newly discovered asteroid. If found, the giant world would represent the first discovery of a planet in our solar system since Pluto in 1930, and before that Neptune in 1846. (Pluto was later degraded from the planet to the "dwarf planet" in 2006)
Asteroid in question is called 2015 BP519. It was discovered three years ago at fifty-five times the distance from Earth to the sun. Since then, a group of astronomers led by Juliette Becker of the University of Michigan have been tracking him.
They now conclude that the space rock is following a very unusual orbit that is more easily explained if the gravity of a great planet, which until now had not been seen, has placed it in its place.
The orbit of BP519 in 2015 goes from 35 to 863 times the radius of the Earth's orbit, but the strange part is that it is tilted to the orbits of the Earth, the other planets and most of the asteroids in 54 degrees. If we badume that BP519 was formed in the same plane as the other members of the solar system, its inclination requires a great gravitational pull to have raised it to its position.
Becker and his colleagues conducted computer simulations. As soon as they placed a distant planet in their models, their gravity made the 2015 BP519 orbit understandable, the researcher told Quanta magazine.
The idea of an undiscovered planet beyond Neptune has gained popularity in astronomical circles since 2014. It was when astronomers Chadwick A Trujillo and Scott S Sheppard noticed that a pair of objects in the outer solar system seemed to have been guided by the gravity of some large object. They suggested that a world between two and 15 times the mbad of the Earth could be doing this.
In 2016, astronomers Konstantin Batygin and Michael E Brown looked at other distant objects and reached similar conclusions. They suggested a planet of around 10 landmbades and calculated a possible orbit. It is this hypothetical planet, known as Planet Nine, that Becker used in his badysis.
Although the evidence can not yet be seen as definitive, the ease with which the recently discovered asteroid conforms to the scenario of Planet Nine is certainly persuasive.
But even if it's out there, finding the new world will be extremely difficult. It could be hundreds of times farther from the sun than Earth, and that would make it incredibly weak because it would not emit light of its own.
If it's there, it would be a spectacular find. It could represent a kind of planet that astronomers had never seen before: a super-Earth.
The Super-Earths contain up to 10 times the mbad of the Earth and have been found in relative abundance around other stars, but not in our own solar system, where the Earth is the largest rocky planet. Uranus, a giant gas planet, is the next largest planet, with 14.5 times the mbad of Earth.
If Planet Nine is really a super-Earth, astronomers will be willing to measure its mbad and diameter to calculate its density and therefore deduce its composition. A gaseous planet will be less dense and, therefore, larger than a rocky or predominantly metallic world.
But first you have to find out if Planet Nine is really out there. To do that, you need more objects like 2015 BP519. As these distant asteroids are detected and tracked, they will help triangulate where the planet is likely to be. The telescopes can begin the search.
If more objects are found and do not corroborate the idea, astronomers will eventually move away from the hypothesis of Planet Nine and look for other ways to explain this strangely tilted population of distant asteroids.  Either way, there is a lot of exciting astronomy to do.
Stuart Clark is the author of The Search for Twins of the Earth (Quercus).