A new study has proposed the existence of Planet Y, an alternative Planet Nine candidate that is smaller and closer to Earth ...

For almost a decade, astronomers have been searching for a ninth planet in the solar system. Recently, new evidence of ...

Is there a massive undiscovered planet on the outer reaches of the solar system? The idea has been around since before the discovery of Pluto in the 1930s. Labeled as planet X, prominent astronomers ...

It's an evocative idea that has long bedeviled scientists: a huge and mysterious planet is lurking in the darkness at the edge of our solar system, evading all our efforts to spot it. Some astronomers ...

Astronomers used a telescope in Hawaii to find a new object on the outer edges of our solar system, helping to fuel evidence of a long-standing theory about Planet Nine, or Planet X. For years, ...

Earth has a newly-discovered neighbor in the solar system. But the heavenly body – possibly a dwarf planet à la Pluto – isn't a frequent visitor. Located beyond Neptune, its extreme orbit ...

Astronomers have observed a massive growth rate in a free-floating rogue planet that’s gobbling up gas and dust at a record ...