This event marks the launch of the Sputnik 10 satellite, which was the tenth satellite of the Soviet Union's Sputnik program. Launched on April 12, 1961, the satellite was the first to successfully reach Earth orbit, and it was the first to carry a living creature into
From Wikipedia
Sputnik 1, often referred to as simply Sputnik, was the first artificial Earth satellite. It was launched into an elliptical low Earth orbit by the Soviet Union on 4 October 1957 as part of the Soviet space program. It sent a radio signal back to Earth for three weeks before its three silver-zinc batteries became depleted. Aerodynamic drag caused it to fall back into the atmosphere on 4 January 1958.