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

Here’s what you should know when you go outside to see for yourself: Yes, the planets are indeed lined up across our sky. No, ...

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

On Feb. 24, from west to east, you can see Mercury, Saturn, Neptune, Venus, Uranus, Jupiter and Mars, all spanning 117.5°, ...