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

All of our solar system’s planets are lining up to parade through the night sky at once. This extraordinary celestial event will see the sky scattered with seven visible planets in what is known ...

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

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

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

In fact, every planet—and every moon—in the solar system will be in the sky during the eclipse. However, that doesn’t mean you’ll see them all. Contrary to what you might have read ...