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 ...

On August 24, 2006, our solar system lost a planet. It wasn't by cataclysmic destruction, but rather by the vote of the International Astronomical Union, which declared that Pluto, considered the ...

A new study suggests yet another theory for a possible extra planet in our solar system, likely of a size between Mercury and ...

IMAP mission will explore our solar system's protective heliosphere and will also help us develop a better understanding of ...