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 ...

Planets may begin forming much earlier than scientists once believed during the final stages of a star s birth, not afterward. This bold new model, backed by simulations from researchers at SwRI, ...

When I was a kid, there were nine planets. Now we know of thousands! But that includes exoplanets, alien worlds that orbit alien suns. Only eight planets call our solar system home. Or there might ...