Astronomers have identified a strange new kind of exoplanet that challenges how scientists classify worlds beyond our Solar System. The planet, L 98-59 d, appears to contain a vast ocean of molten ...

Astronomers believe they have uncovered evidence of a previously unknown ninth planet lurking in the not-too-distant reaches of the solar system. This hypothetical world, dubbed "Planet Y," could be ...

WASHINGTON — Stargazers will have a special chance to see seven planets align in the night sky this week as Mercury joins Venus, Mars, Jupiter, Saturn, Uranus and Neptune in a planetary parade. In ...

Add Yahoo as a preferred source to see more of our stories on Google. An illustration showing Planet Nine, a hypothetical, undiscovered planet in our solar system. New research now suggests the ...

Astronomers have detected an Earth-size planet candidate orbiting a nearby star once a year, making it a promising target for future studies.

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 ...