COLORADO SPRINGS, Colo. - Forty years ago this month, NASA launched the last of two space probes that continue to work and are now heading out of our solar system.
Voyager 1 launched on Sept. 5, 1977, and Voyager 2 took off nearly three weeks earlier, from Cape Canaveral, Florida.
The probes were built to study the outer solar system and are now exploring the area just beyond the sun's influence (the heliosphere) in interstellar space, the first human-made objects to do so.
NASA expects the probes to continue working and sending back data until 2021, when the probes likely will run out of power and be deactivated.
The probes were launched in 1977 to take advantage of a favorable alignment of Jupiter, Saturn, Uranus and Neptune.
Studying the planetary systems of Jupiter and Saturn was the probes' original mission, but they also recorded 10 more moons and a magnetic field around Uranus, as well as three rings, six new moons and a magnetic field around Neptune.
An interesting feature of the probes is the inclusion of a 12-inch phonograph record made of gold, containing images and sounds of Earth along with symbols showing how to play the record and how to find our planet.
NASA intends the records to serve as a time capsule and a message to any intelligent civilization that may someday find the probes.
In recent years, some experts have come to believe that placing such information in an interstellar probe, where a civilization of unknown intent may find it, could someday be dangerous for Earth.