A newly discovered warp in the outer Solar System may have been created by a small, rocky world, much closer to the Sun than ...

Pluto's unusual eccentricity and tilt is likely due to its interactions with neighboring Neptune and other giant planets, ...

The methane gas may constitute a rarefied atmosphere, or it may come from erupting plumes on Makemake’s surface.

Astronomers using the Hubble Space Telescope have uncovered the remains of a frozen, Pluto-like world being devoured by a distant white dwarf star.

Comet Lemmon will have its closest brush with Earth on or around Tuesday, Oct. 21. Comet SWAN should have its flyby with ...

Two bright green comets are streaming through the skies and are visible to skygazers in the Northern Hemisphere.