Forget Planet Nine, there could be something even stranger at the edge of our solar system - a hidden black hole.
Some scientists believe that a huge planet that has never been seen by astronomers could be lurking, almost invisibly, at the dark edges of our solar system.
The evidence is the strange orbits of rocks beyond Neptune, although the planet itself has stubbornly evaded detection.
But a new pre-print science paper argues that there could be something even weirder out there - a ‘primordial black hole’.
Researchers from the UK and US suggest that a primordial black hole, which formed at the beginning of the universe could be lurking at the edge of the solar system.
Primordial black holes are a theoretical object, and are thankfully much smaller than the monstrous black hole that lurks at the centre of our Milky Way, with some suggesting the object could be as small as a bowling ball.
Researchers led by Professor James Unwin at the University of Illinois at Chicago suggest that a ‘more exciting’ possibility might be that a black hole lurks at the edge of our solar system.
Unwin told Gizmodo, ‘Once you start thinking about more exotic objects, like primordial black holes, you think in different ways.
‘We advocate that rather than just looking for it in visible light, maybe look for it in gamma rays. Or cosmic rays.’
Many scientists believe that there’s a large, unseen planet at the very edge of our solar system, due to the wobbly orbits of rocks beyond Neptune.
But it’s likely to be extremely dim, as it’s so far from the sun, so it could be up to 1,000 years before the planet is spotted.
Some of the rocks out there - trans-Neptunian Objects (TNOs) - have distinctly odd orbits, which has led some scientists to believe there’s a planet out there.