We’ve found lots of “habitable” worlds but we don’t know what factors are needed for life. There are lots of reasons to search for planets around other stars—exoplanets. A big one is to find other ...

Astronomers are closing in on one of the most tantalizing possibilities in planetary science, evidence that a previously unknown world may be lurking in the outer reaches of the solar system. The ...

Easy: Venus is the weirdest planet in the solar system. The most distant major planet from the sun and the last stop before ...