Our solar system may have a ninth planet after all, following the declassification of Pluto nearly two decades ago, ...

Astronomers have found new evidence that a mysterious ninth planet may be hiding at the edge of the solar system ... size of Uranus or Neptune. Just like these distant ice giants, however, Planet ...

A powerful new observatory is the best hope yet for finding the elusive Planet 9, a large planet that some scientists say is hidden in our solar system.

Saturn orbits the Sun at roughly 9.69 km/s, maintaining its grand system of rings as it cruises through space. Uranus moves at about 6.81 km/s, spinning on its unique sideways axis as it orbits ...

"We don't know the size of the planet ... "But I just don't see a way that the solar system can exist the way it does without there being a Planet 9." As this year progresses, he says, the ...

K2-18 b, which sits in the Leo constellation, is nearly nine ... Planets beyond our solar system are too distant to photograph or reach with robotic spacecraft. But scientists can estimate their ...