A new study suggests yet another theory for a possible extra planet in our solar system, likely of a size between Mercury and ...

Astronomers have discovered fresh evidence suggesting the possible existence of an unseen planet in the far reaches of our ...

This article was originally featured on The Conversation. Are planets in the solar system that are closer to the Sun older than the ones further away? – Gavriel, age 10, Paducah, Kentucky A cloud of ...

WASHINGTON (Reuters) -Just as Earth orbits the sun, most planets discovered beyond our solar system orbit a host star.