Sputnik 1 became the first artificial satellite when the Soviet Union launched it on 4 October 1957.
The small spherical spacecraft was launched from Baikonur Cosmodrome aboard a modified R-7 rocket. It transmitted regular radio beeps that could be detected by radio operators around the world. Although its scientific instruments were limited, the satellite demonstrated that the Soviet Union could place an object into orbit and operate it in space.
Sputnik 1 orbited Earth at an altitude of roughly 215 to 939 kilometres and completed one orbit in about 96 minutes. Its launch shocked the United States and helped trigger the Space Race, accelerating American investment in rockets, satellites and human spaceflight.
A common mix-up is confusing Sputnik 1 with Sputnik 2. Sputnik 2 followed less than a month later and carried Laika, the first animal to orbit Earth. The United States launched its first satellite, Explorer 1, in January 1958.