On August 20, 1977, NASA launched a pair of space probes into the cosmos, sending them on a journey to observe our celestial neighbors. Traveling at 35,000 miles per hour, Voyager 1 and 2 have ventured more than 11 billion miles from Earth, exploring the solar system — capturing up-close images of Jupiter, Saturn, Uranus and Neptune — before hurtling toward interstellar space.