EpimetheusJust days after the discovery of a satellite in a near-identical orbit, U.S. Naval Observatory astronomer Richard Walker discovers Epimetheus, another natural satellite of the planet Saturn, again orbiting just beyond the outer edge of Saturn’s ring. Many of Walker’s fellow astronomers believe this is merely a second sighting of Janus, discovered mere days before, but irregularities in the computed orbits vex astronomers well into the 1970s, at which point it is conceded that the observations are best explained by two satellites in a very close orbit to one another. Epimetheus and Janus will next be spotted by Voyager 1 in 1980, conclusively proving the existence of two bodies. Epimetheus’ name won’t be made official until 1983. (Epimetheus is shown here in a 21st century Cassini photo.)

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