"artificial satellite," 1957 (launched Oct. 4, 1957), from Russian sputnik "satellite," literally "traveling companion," from Old Church Slavonic supotiniku, from su- "with, together" + poti "way, journey" (from PIE root *pent- "to go, pass;" see find (v.)) + agent suffix -nik.
The electrifying impact of the launch on the West can be gauged by the number of new formations in -nik around this time (the suffix had been present in a Yiddish context for at least a decade before); e.g. the dog launched aboard Sputnik 2 (Nov. 2, 1957), which was dubbed muttnik by the "Detroit Free Press," etc., and the U.S. satellite which failed to reach orbit in 1957 (because the Vanguard rocket blew up on the launch pad) derided as a kaputnik (in the "Daily Express"), a flopnik ("Daily Herald"), a puffnik ("Daily Mail"), and a stayputnik ("News Chronicle").
A series of Soviet satellites launched in 1957 and in following years. These were the first artificial satellites.
Note: The appearance of Sputnik stimulated a great deal of effort in the education of scientists and engineers in the United States. This period is now referred to as the post-Sputnik boom.