On Aug. 20, 1977, NASA launched the Voyager 2 spacecraft on a mission to explore the outer planets. Despite its name, this was the first of two Voyager missions NASA launched that year. Thanks to a rare alignment of the planets, NASA had the opportunity to send a spacecraft on an unprecedented journey to Jupiter, Saturn, Uranus and Neptune. While Voyager 1 ended its planetary mission after Saturn, Voyager 2 completed a 12-year journey to Neptune. But they didn't stop there! Voyager 1 left the solar system and entered interstellar space in 2012, and Voyager 2 is expected to do the same by the year 2020.
