Pluto was reclassified as a dwarf planet in 2006. Our solar system may have a ninth planet after all, researchers say. The possibility that an additional planet may be hidden far into the solar system ...

Caltech professor Mike Brown (L) and assistant professor Konstanin Batygin have been working together to investigate distant objects in our solar system for more than a year and a half. The two ...

If the solar system does have a Planet Nine, it is a world that was bullied by its larger siblings, exiled to the far reaches of space and only rescued from oblivion thanks to the intervention of ...