A space probe is an unmanned spacecraft that flies into outer space. It may land on the Moon or other planets, go into orbit around them, or fly past them. Its purpose is to conduct research: It contains cameras and other advanced equipment so that it can send pictures back to Earth by radio. The first successful space probe took place in 1959 with the Soviet Luna 1, which passed within 3,725 miles (5,995 kilometers) of the Moon’s surface after 83 hours of flight. It then went into orbit around the Sun, between the orbits of Earth and Mars. In 1977, the United States launched Voyager 1 and Voyager 2 from rockets. These space probes explored all the giant planets of our outer solar system (Jupiter, Saturn, Uranus, and Neptune), 48 of their moons, and the unique system of rings and magnetic fields for each of those planets.