Add Yahoo as a preferred source to see more of our stories on Google. Jupiter is already the biggest planet by far in our solar system, but new research suggests it was somehow once even larger than ...

CAPE CANAVERAL, Fla. - Astronomers have found a nearby solar system with seven Earth-sized planets, three of which circle their parent star at the right distance for liquid surface water, bolstering ...

To be a planet, NASA says an object must be big enough that its gravity has cleared away any other objects of a similar size ...

This article was originally published at The Conversation. The publication contributed the article to Space.com's Expert Voices: Op-Ed & Insights. The size of the solar system is defined by the volume ...

Five years ago, astronomers revealed a spectacular collection of other worlds: the TRAPPIST-1 system. Newspapers around the world printed the discovery on their front pages: Astronomers had found that ...