It may initially seem like a simple question, but determining which planet is closest to Earth is surprisingly tricky and can have multiple correct answers. When you purchase through links on our ...

A quartet of Earth-like worlds, each about 20% to 30% the size of our planet, circle one of our closest stellar neighbors, a new study reveals. The rocky alien worlds are close enough that future ...

The Trappist-1 system, just 40 light years from Earth, contains 7 rocky planets - all roughly the size of Earth. Packed tightly within the space between Mercury and the Sun, three of these planets lie ...

The James Webb telescope has made another stunning discovery -- this time of a massive planet that could potentially sustain ...

But it also happens to be the closest 'Earth-like' planet that researchers know of. Hundreds of planets found outside of our solar system are Earth-sized and may be habitable.

But it also happens to be the closest 'Earth-like' planet that researchers know of. Hundreds of planets found outside of our solar system are Earth-sized and may be habitable.

Earth, Mars and Venus all looked pretty similar when they first formed. Today, Mars is dry, cold, and dusty; Venus has a hot, crushing atmosphere. Why did these sibling planets turn out so different?