While the composition of gas and dust in a molecular cloud is fairly uniform, everything changes once a star begins to form.

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

Helium can help scientists detect the speed and direction at which we’re moving through space. Deuterium, which is left over ...

All seven of the other planets in our solar system are about to become visible at once in a great planetary alignment – ...

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

On the evening of February 28, stargazers will witness a rare celestial event: an alignment of seven planets visible ...

A planet-size object that possibly once visited the solar system may have permanently changed our cosmic neighborhood by warping the orbits of the four outer planets, a new study suggests. The ...