The small world was found during a search for the hypothetical Planet Nine, and astronomers say the next time it will reach ...

A recent study found that Jupiter was once twice the size that it is now, making it big enough to swallow up 2,000 Earths.

Solar scientists have unveiled spectacular new images of plasma "rain" in the sun's corona using adaptive optics.

An alternate explanation that fits the evidence is that Vesta was once part of a planet – but which planet that might been remains a mystery.

(NASA's Juno craft, exploring the greater Jupiter system, also carries a vault.) Mashable Light Speed Want more out-of-this world tech, space and science stories? Sign up for Mashable's weekly ...

This story is part of Short Wave's series Space Camp ... you might have memorized that there were nine planets in our solar system, as heard in the famous Schoolhouse Rock! song, Interplanet ...