For the dwarf planet candidate, one trip around the sun takes over 24,000 years. Its orbit challenges a proposed path for a hypothetical Planet Nine.

Some scientists hypothesize that a mysterious, gigantic 9th planet may be lurking at our solar system’s edge. Why haven't we ...

Planet X, also called Planet Nine, is a hypothetical planetary body seven times the mass of Earth lurking behind Pluto. If found, this gassy, icy beast some 155 billion miles away from the Sun ...

Scientists may have discovered a dwarf planet far beyond Neptune — an unearthing that may disprove a longstanding theory ...

No telescope has basked in the night sky quite like the enormous new Vera Rubin Observatory. Here's what it could reveal ...