For the better part of a century, we believed there were nine planets in our solar system, with Pluto being the farthest from the sun. Since the discovery of more Pluto-sized dwarf planets, that ...

For decades, Pluto was our solar system's ninth planet. This video explains the scientific journey that led to its ...

There have been questions about a mysterious ninth planet in our solar system for nearly a decade. Pluto was unseated as number nine in 2006. Now, a group of international researchers say they may ...

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 ...

On July 14, 2015, NASA's New Horizons spacecraft arrived at Pluto for the first time. The craft flew within 7,700 miles of the planet and is sending back reams of data and the highest resolution ...

Earth has a newly-discovered neighbor in the solar system. But the heavenly body – possibly a dwarf planet à la Pluto – isn't a frequent visitor. Located beyond Neptune, its extreme orbit ...

When I was a kid, there were nine planets. Now we know of thousands! But that includes exoplanets, alien worlds that orbit alien suns. Only eight planets call our solar system home. Or there might ...

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 ...

WASHINGTON (AP) — There’s a chaotic dance going on at the far end of our solar system, involving Pluto and five of its closest friends, a new study finds. Hubble Space Telescope images of Pluto, its ...

New high-contrast images from SPHERE show a stunning variety of debris disks shaped by collisions of tiny planet-building ...

Nearly a century after Pluto’s discovery, astronomers are still hunting for mysterious planets beyond Neptune - including a ...