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

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.

The planet, which astronomers believe is orbiting a young red dwarf star approximately 34 light years away, has been dubbed ...

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 ...

Despite this, "people have considered a whole host of different orbits for these hypothetical planets," Chad Trujillo, an astronomer at Northern Arizona University, said to Science News. "This object ...

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