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

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

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

The formation of our solar system from a singular nebula raises an intriguing question: why did each planet develop with a ...

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