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

Think of the solar system as a fried egg; the sun is the yolk and the planets each draw circles in the white, all going the same direction. Now, think of the sun’s path through our daytime sky.

But the auroras on Uranus prove that the lights are beautiful anywhere in the solar system, appearing as thin streaks of bright white light set against the deep azure background of the planet.

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

With the exception of Pluto, planets in our solar system are classified as either ... and trace amounts of other gases. White clouds of water vapor hide much of Earth's surface in views of Earth ...