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Scientists may have discovered a dwarf planet far beyond Neptune — an unearthing that may disprove a longstanding theory about the possibility of a giant ninth planet. The dwarf planet's existence ...

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 ...

Astronomers are closing in on one of the most tantalizing possibilities in planetary science, evidence that a previously unknown world may be lurking in the outer reaches of the solar system. The ...

When you see art of our solar system as the planet orbit the sun, you may notice that Earth's orbit has a tilt. It is not a perfect circle. What's more, Earth is not the only planet that displays such ...

Astronomers studying the Kuiper Belt have detected a strange distortion that could point to an unknown planet lurking far beyond Neptune.

A new Tatooine-like planet outside the solar system may orbit two failed stars, scientists reported Wednesday. Located about 120 light years away, the exoplanet appears to take an unusual path around ...