Certain extreme planets are called ultra-short period objects if they're very close to their stars and orbit them in mere hours, like K2-22b.

A spacecraft has sent back some of the most detailed and breathtaking images of Mercury's north pole, shedding new light on the mysterious, shadowy regions of the small planet closest to the Sun.

Ceres, the largest object in the asteroid belt, is a dwarf planet with frozen oceans and hints of ancient habitability, setting it apart from its rocky neighbors. With a solid core, icy mantle ...