The head of NASA says maybe Pluto is a planet after all. He is wrong because Pluto is part of the rest of the solar system ...

A distant, frozen world has been discovered far beyond Pluto. This video explores its extreme orbit, strange composition, and ...

Add Yahoo as a preferred source to see more of our stories on Google. An illustration showing Planet Nine, a hypothetical, undiscovered planet in our solar system. New research now suggests the ...

Astronomers are closing in on one of the most tantalizing possibilities in planetary science, evidence that a previously unknown world may be lurking in the outer reaches of the solar system. The ...

In the remote outer reaches of planetary systems, far beyond the orbit of known planets, enormous and mysterious worlds silently loop around their stars. Some drift as far as 10,000 times the distance ...

There may be a warp in the Kuiper Belt, possibly caused by “Planet Y” — a Mercury-to-Earth-sized world that orbits the sun way beyond the orbit of Neptune. Is there a mysterious “Planet Y” orbiting ...

A strange planetary system called TOI-201 is changing in real time, with three very different worlds pulling on each other.

New simulations suggest binary star systems may be ideal for planet formation, and may produce more gas giants than ...