On Aug. 20, 1977, NASA launched the Voyager 2 spacecraft on a mission to explore the outer planets. Despite its name, this ...

What is the difference between a moon and a planet?Trick question! According to scientific definitions, there often isn’t much of a difference at all. That might seem counterintuitive, but it’s true.

Mark your calendar so you can catch Mercury, Venus, Jupiter, Saturn, Neptune and Uranus in the sky at the same time.