Voyager 1 is a robotic spacecraft launched to explore the outer solar system by NASA. It was launched from Cape Canaveral on September 5, 1977 and has since toured the major planets, using each for a gravity assist, to alter the speed and trajectory of the craft. Voyager 1 passed by Jupiter on July 9, 1979 and Saturn on August 25, 1979. Voyager 2, its twin, also passed by Neptune and Uranus. With these two craft (plus the earlier Pioneer missions) much more information was learned about these outer planets.
As of February 2008, Voyager 1 was at a distance of 9.8 billion miles (105.3 Astronomical Units (AU)) from the Sun. Voyager 1 is escaping the solar system at a speed of about 3.6 AU per year. Voyager 1 crossed the termination shock (the area of space where the solar wind approaches the boundary of the heliosphere and abruptly slows down to about 250,000 miles per hour) on December 16, 2004.