Astronomers propose a new hypothetical planet, Planet Y, beyond Neptune, based on observed orbital anomalies in the Kuiper ...

Currently, our solar system recognizes 8 planets, with Pluto being demoted to a dwarf planet floating in the Kuiper Belt in 2006. Planet Nine's gravitational pull may explain what keeps the icy ...

New discoveries of objects in the Kuiper Belt have also presented challenges for the Planet Nine theory. The latest is known ...

Only eight planets call our solar system home. Or there might still be nine if some astronomers are correct about an as-yet undiscovered large body out past Neptune.

For now, the outer reaches of our 4.6 billion-year-old solar system continue to be shrouded in mystery, with the classification of objects changing as scientists gain a new understanding of them ...

The last real planet to be discovered in our solar system was Neptune in 1846. Pluto, discovered in 1930, was once the 9th planet but is now considered a dwarf planet in the Kuiper Belt.

This hypothetical planet, according to the team, could now be a rogue, or lurking at the edge of the Solar System as the elusive "Planet 9".

"This is the 5th largest planet in our solar system, lurking out there, waiting to be found," the Caltech astronomer says. For about a decade, he and other researchers have been trying to prove ...

If Planet Nine exists, it would therefore perhaps have to be farther than 500AU away from the Sun. To make matters worse for the Planet Nine theory, this is the fourth sednoid to be discovered.