Evidence that rocky planets beyond Jupiter formed as rapidly, and at the same time, as the inner planets could transform our ...

Previously, astronomers have observed giant planets, like Jupiter, forming in the giant discs around young stars. According ...

In a cosmic first, scientists identified signs of early planet formation by looking deep into the gas disk around a baby star ...

In the dark, icy outskirts of our solar system—far beyond Neptune's orbit—astronomers have discovered a cosmic oddball that ...

A possible dwarf planet, like Pluto, has been observed in our solar system, according to a preprint published in arXiv. The area of space where this planet was found was previously thought empty.

All eight of the solar system’s “major” planets appear in this illustration, but the actual number of planetary bodies orbiting our star is far greater. Digital Vision/Getty Images.

Our solar system may have a ninth planet after all, following the declassification of Pluto nearly two decades ago, researchers say. ABC News. Live. Video. Shows. Shop. Log In. Stream on.

If there were one, that Planet Nine would "nudge the closest part of 2017 OF201's trajectory inward until Neptune flung it out of the solar system." Because 2017 OF201 is there, that could be an ...