Our Sun had a companion and there could be many undiscovered dwarf planets in the outer Solar System. That’s according to a new paper from scientists from Harvard University. Published today in ...

Big bully? A jealous Planet Nine may have shoved its siblings for attention. If a massive ninth planet exists in our solar system , it might explain why the planets are out of line with the sun.

June 5 Raking sunlight highlights the texture of the dwarf planet, including a large crater, at lower left, in Ceres’s southern hemisphere. This image was taken from a low altitude of 2,700 miles.

Planetary scientists are proposing a new definition of a planet to replace one that many researchers view as sun-centric and outdated. The current definition — established in 2006 by the International ...