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

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 ...

Far beyond Neptune, something massive may be warping the orbits of distant worlds. This film follows the scientists chasing Planet 9 — and the evidence that keeps them searching.

"It is possible that a planet once existed in the solar system but was later ejected, causing the unusual orbits we see today." Astronomers have discovered a massive new solar system body located ...

At the edge of the Solar System, strange orbital patterns hint at the presence of a massive unseen planet. This investigation follows the scientists searching for Planet Nine, a potential world large ...

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A mysterious "rogue planet" has been observed gobbling 6 billion tons of gas and dust a second — an unprecedented rate that blurs the line between planets and stars, astronomers said Thursday. Unlike ...