The solar system lost its ninth planet back when Pluto was demoted to a dwarf planet, but research might indicate that there ...

Astronomers may have demoted Pluto from full-fledged planet to dwarf status, but evidence suggests the solar system may still ...

A pair of theoretical physicists are reporting that the same observations inspiring the hunt for a ninth planet might instead be evidence within the solar system of a modified law of gravity ...

Pluto has long been one of the most debated celestial bodies in our solar system. Once classified as the ninth planet, it was redefined in 2006 as a dwarf planet, a decision that still sparks ...

CAPE CANAVERAL, Fla. -- Scientists reported Wednesday they finally have "good evidence" for Planet X, a true ninth planet on the fringes of our solar system. The gas giant is thought to be almost as ...

The solar system may have a ninth planet after all. This one is 5,000 times bigger than outcast Pluto and billions of miles farther away, say scientists who presented "good evidence" for a ...

There has been a lot of back and forth about the existence of a mysterious ninth planet, often referred to as "Planet Nine" or even "Planet X." Now, though, researchers say there is likely at least a ...

Think you know Pluto? From icy plains to planetary debates, this quiz dives deep into the mysteries of our solar system’s most controversial—and captivating—dwarf planet.

The science community may be ecstatic over the discovery of a ninth planet, but the former planet "Pluto" had a totally different reaction. Hours after scientists announced there's solid evidence of ...

A recent research paper suggests that a planet may exist far beyond Neptune — less than 20 years after the previous ninth planet, Pluto, was demoted. That research paper, accepted last month for ...