The number of planets that orbit the sun depends on what you mean by “planet,” and that’s not so easy to define ...

Scientists studying samples that NASA collected from the asteroid Bennu found a wide assortment of organic molecules that ...

A U.S. scientist searching for a civilization across 7 Earth clones circling the red dwarf star TRAPPIST-1 says its own alien ...

An object eight times the mass of Jupiter may have swooped around the sun, coming superclose to Mars' present-day orbit ...

The building blocks of life could have been delivered to Ceres by one or more space rocks from the outer asteroid belt.

The enormous visitor to our solar system may have been about 8 times the mass of Jupiter, and come nearly as close to the sun ...

Planets with suns like Wolf 359 are subject to huge blasts of radiation that raise questions about their long-term ...

When astronomers found a large world farther out than Pluto, it became one of the final nails in the coffin of our ninth ...

Stargazers will be treated to a dazzling six-planet "alignment" this January.

A new study suggests that a planet-sized object may have passed through the solar system billions of years ago.

An object we thought belonged to the most common category of planet in the galaxy has turned out to be something we've never ... because we have nothing directly analogous to them here in our Solar ...