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

Worlds with liquid water could have formed just 200 million years after the big bang from the remains of the earliest ...

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

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

Certain extreme planets are called ultra-short period objects if they're very close to their stars and orbit them in mere hours, like K2-22b.

Thirty years after the discovery of the first exoplanet, we detected more than 7000 of them in our Galaxy. But there are ...

Six planets grace the sky this month in what's called a planetary parade — Venus, Mars, Jupiter and Saturn are visible to the ...