A newly discovered warp in the outer Solar System may have been created by a small, rocky world, much closer to the Sun than ...

Siraj’s Planet Y search started about a year ago when he was trying to find out whether the shape of the Kuiper Belt is flat. “The planets of the solar system have slight tilts up and down, but ...

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 ...

Scientists think there may be a ninth planet hiding in the distant reaches of the solar system — and a new telescope could finally prove its existence. | Credit: Nicholas Forder for Live Science Deep ...

Astronomers have discovered a brand-new world hiding out beyond Pluto. While exciting, the discovery of this new world could challenge long-standing theories of the existence of Planet Nine. In fact, ...

How can we figure out if the planet is actually there? And will it even be bright enough to see? Here are some answers to these and other pressing questions. Others aren’t quite so sure. “I’m very ...

As the world marvels at the first-ever close-up images of Pluto beamed to Earth, it is a reminder of a sharp global division: those with nine-planet childhoods vs. those now growing up in a solar ...