Is an extra world hidden on the edge of our solar system?
Evidence that Planet Nine does exist piles up as experts spot a distant object with an 'extraordinary orbit'
An undiscovered world may be lurking in the outer reaches of the solar system. Astronomers have debated whether an elusive ninth planet orbits beyond Pluto for years, but a new study may finally prove the mysterious world is real.
Researchers have spotted a distant rocky object that they suggest was pushed into an 'extraordinary orbit' by the gravitational pull of an uncharted planet. They say that their finding bolsters the ever- convincing case that a so-called 'Planet Nine' exists.
Planet Nine was first theorised by experts at Caltech in 2016 when they spotted that a group of icy objects on the edges of the solar system have tilted orbits. They suggested the orbits of these lumps of ice - so-called TransNeptunian objects (TNOs) - were warped by the gravitational pull of a ninth planet in the solar system. The objects had elliptical orbits that pointed in the same direction and were tilted 30 degrees 'downward' compared to the plane in which planets circle the sun.
While Planet Nine has never been spotted, a number of astronomers - including scientists at Nasa - have since released research that supports the theory.
In a new paper, a group of experts led by the University of Michigan describe a distant object that they spotted in 2014 that could be as large as a dwarf planet. The rocky body, dubbed 2015 BP519, peaked the team's interest because its orbit is unusually tilted away from the plane that most objects that orbit the sun lie. They used computer simulations of the solar system to explore how this strange trajectory may have arisen.
Simulations where our star system had eight planets did not reproduce 2015 BP519' s tilted orbit. When researchers added a ninth planet that matched the properties of those proposed by the Caltech researchers, the simulation reproduced 2015 BP519's current orbit almost exactly.
'It's not proof that Planet Nine exists,' Professor David Gerdes, an astronomer at the University of Michigan and a co-author on the new paper, told Quanta. ' But I would say the presence of an object like this in our solar system bolsters the case for Planet Nine.'
The study adds to piling evidence for the existence of Planet Nine, though astronomers remain latched to their telescopes in search of the object.
In October 2017 Nasa weighed in on the debate, highlighting five different lines of evidence pointing to the existence of the object. It said that imagining that Planet Nine does not exist generates more problems than it solves.
Dr Konstantin Batygin, a planetary astrophysicist at Caltech in Pasadena, whose team is closing in on finding Planet Nine, said: 'There are now five different lines of observational evidence pointing to the existence of Planet Nine. If you were to remove this explanation and imagine Planet Nine does not exist, then you generate more problems than you solve. All of a sudden, you have five different puzzles, and you must come up with five different theories to explain them.'
The researchers now hope to find Planet Nine itself using the Subaru Telescope at Mauna Kea Observatory in Hawaii, which they describe as the 'best tool' for the job.