HD 209458 b, nicknamed "Osiris," is one of the first exoplanets seen passing in front of its star, and it's about 159 light-years from Earth. Kepler-186f is the first Earth-sized planet discovered in ...

Kepler-22b is a “super-Earth,” about 2.4 times Earth’s size. Scientists do not yet know if the planet has a rocky, gaseous, or liquid composition. It's possible that the world would have clouds in its ...