In A Nutshell Arrokoth, a snowman-shaped object billions of miles from Earth, is one of the oldest and least-disturbed relics of the early solar system Scientists have long debated whether its two ...

Astronomers have found a distant world that challenges planetary formation theory, with a rocky planet where gas giants should be.

A newly studied solar system breaks the usual planet pattern, raising fresh questions about how rocky and gas planets form.

Astronomers have found a rocky planet where it should not exist, orbiting far from a cool red star. Could this strange ...

The discovery provides new insights into the question, 'how large can a planet be?' An illustration of the HR 8799 system with three of its gas ...