Astronomers have found a pair of asteroids in the outer Solar System that appear to have been affected by Planet Nine, a hypothetical world that orbits far beyond Pluto.
A study describing the findings, published in the Monthly Notices of the Royal Astronomical Society, builds on research that first theorized Planet Nine’s existence last year. The world is thought to be more than 10 times the size of Earth, and orbits more than 200 times the Earth-Sun distance.
Planet Nine’s existence was inferred from the peculiar orbits of some objects in the outer Solar System, such as extreme trans Neptunian objects (ETNOs). The extremely elliptical orbits of several bodies orbiting far from the Sun suggests a large, unseen world has been gravitationally tugging on them.
Scientists from the Canary Islands Institute of Astrophysics (IAC) looked at two of these bodies in particular, the asteroids 2004 VN112 and 2013 RF98, which have similar sweeping orbits around the Sun. Studying their composition, they found that they likely had a similar origin – suggesting they were once a binary asteroid pair that was pulled apart.
After performing thousands of numerical simulations, the team found that a planet with a mass of between 10 and 20 Earths – predicted for Planet Nine – could have caused the pair to split about 5 to 10 million years ago.
"The similar spectral gradients observed for the pair 2004 VN112 – 2013 RF98 suggests a common physical origin," explains Julia de León, the first author of the paper and an astrophysicist at the IAC, in a statement. "We are proposing the possibility that they were previously a binary asteroid which became unbound during an encounter with a more massive object."
The search for Planet Nine is continuing in earnest. At the moment, we’ve only got indirect evidence for its existence. But some are sure it’s out there – and studies like this help us further refine exactly what part it may play in the Solar System.