The mystery of Planet 9 has deepened. New research suggests that if the oft-debated, hypothetical planet does exist, it isn't an original member of our solar system.
A computer simulation designed by Lund University, Sweden, suggests 'Planet 9' is a misnomer, and that it's actually an exoplanet that was "stolen" from another star by our Sun.
"It is almost ironic that while astronomers often find exoplanets hundreds of light years away in other solar systems, there's probably one hiding in our own backyard," said lead researcher Alexander Mustill.
The existence of Planet 9 was first suggested in 2014, in a letter to Nature by astronomers Chad Trujillo and Scott S. Sheppard. They suggested there may be a "massive trans-Neptunian planet" on the outskirts of our solar system due to "similarities in the orbits" of distant objects that orbit Neptune.
Later, researchers from the California Institute of Technology argued a huge outer planet would indeed be the most likely reason why several distant objects had a similar orbit. For example, the gravitational pull of the planet would force them into similar patterns.
Many of these distant objects had "large orbital eccentricities and inclinations" suggesting an external force was having an effect on them.
The new simulation suggests the planet does exist but that it was "stolen" from its orbit around another star. When our Sun passed another star - possibly from the same cluster - it may have pulled the exoplanet into its orbit.
Planet 9 may also have been "shoved" to the edge of its original solar system by other planets, the star shows.
"Planet 9 may very well have been shoved by other planets, and when it ended up in an orbit that was too wide around its own star, our Sun may have taken the opportunity to steal and capture Planet 9 from its original star," said Mustill.
When the Sun eventually left the star cluster from which it was born, Planet 9 then became "stuck in an orbit" around it.
Despite the new simulation, much of what we know about Planet 9 is hypothetical. We have no images of the planet, for example, and "not even a point of light".
We don't even know whether it's made up of rock, ice or gas.
"All we know is that its mass is probably ten times the mass of Earth," said Mustill.
This article was originally published by WIRED UK
