The new plot twist is that in order to keep enough nitrogen and phosphorus near its surface, a planet has to start out with ...

Relative sizes of the newly discovered habitable-zone planets and Earth. Left to right: Kepler-69c, Kepler-62e, Kepler-62f and Earth (except for Earth, these are artists' renditions). Image credit: ...

For the first time in years, astronomers are seriously talking about adding a new member to the solar system’s planetary family. I’m not talking about reviving Pluto’s status, but about a potential ...

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 ...