Using two infrared space telescopes and a 23-year gap, scientists may have spotted a mysterious, slow-moving object beyond ...

The presence of another planet in the solar system could explain the odd movements of some of the bodies in the Kuiper Belt.

If the object really is Planet Nine, it would be larger than Neptune and exist 700 times further from the sun than Earth.

The solar system consists of our star, the sun, and everything bound to it by gravity: the planets Mercury, Venus, Earth, ...

A new look through decades-old data has unveiled some of the most compelling evidence yet of a hidden ninth planet in the far ...

Astronomers have detected a promising sign of a ninth planet lurking at the the farthest reaches of the Solar System.

A rare and dramatic scene unfolds 140 light-years from Earth. A rocky planet, once whole, is now crumbling to dust under the ...

A team of astronomers poring through old astronomical data may have seen a candidate for the elusive Planet Nine – a ...

Astronomers from MIT have uncovered a dramatic celestial spectacle: a Mercury-sized exoplanet that is rapidly disintegrating ...

A Harvard professor questions whether research conducted at the University of Cambridge about life on K2-18b is accurate.

Some scientists are convinced that beyond Neptune, there's a planet they've yet to see. This so-called "Planet 9" is so far ...