They seemed large enough to be planets; all of them are roughly the same size as Pluto. Astronomers then surmised that there were likely many more of these icy bodies in the Kuiper belt.

Astronomers have discovered an Earth-size planet orbiting a red dwarf star, making just the second planetary system seen around one of these tiny, cool, dim, but common, stars.

CAPE CANAVERAL, Fla. (AP) — Talk about an Earth-shattering discovery. Scientists have spotted seven Earth-size planets around a nearby star, some or all of which could harbor water and possibly ...

Curious Kids is a series for children of all ages. Have a question you’d like an expert to answer? Send it to . “Comet,” “star” and “planet” are category names that immediately tell ...

Prior to flybys, scientists used mathematical laws and observation to determine the characteristics of the planets.

And in order to form a cloud that big, the scientists calculated that the objects colliding must have been massive, the size of dwarf planets in our own neighborhood.

A new study sheds light on what Jupiter, often called the "architect" of the solar system, was like in the beginning. The giant planet has dramatically changed.

The James Webb Space Telescope has detected a possible gas giant the size of Saturn in the stellar system nearest our own ...