This video examines the ongoing search for a hypothetical planet far beyond Neptune, often referred to as Planet X. Strange ...

In a blow to anyone dreaming that complex life may exist elsewhere in the universe, a new study suggests we're unlikely to find it around many of the most common stars in the galaxy. Earth-like ...

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 ...

LONDON — The search for an unknown planet in our solar system has inspired astronomers for more than a century. Now, a recent study suggests a potential new candidate, which the paper's authors have ...

Astronomers are intensifying the search for the hypothetical planet nine, a massive world thought to orbit far beyond Neptune ...