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 found new evidence, revealing the existence of an unseen and mysterious planet that could be hidden in the ...

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

A recent study introduces a potential new candidate, dubbed Planet Y, inferred from the tilted orbits of distant objects in the Kuiper Belt.

While Planet Y has been not yet been directly observed, unexpected inclinations found in the orbits of roughly 50 distant ...

On August 24, 2006, our solar system lost a planet. It wasn't by cataclysmic destruction, but rather by the vote of the International Astronomical Union, which declared that Pluto, considered the ...

There have been questions about a mysterious ninth planet in our solar system for nearly a decade. Pluto was unseated as number nine in 2006. Now, a group of international researchers say they may ...

Space scientists look back on 30 years of exoplanet discoveries — from rows of massive ‘super-Earths‘ to worlds with ...

From lava worlds to gas giants, NASA says the variety of these worlds is staggering—and that signs of a further 8,000 distant ...

Exoplanet hunters Christopher Watson and Annelies Mortier explain the long search for a 'twin Earth' capable of sustaining ...