Cassini, Giovanni Domenico 1625-1712
French astronomer

Born in Perinaldo, near Nice, France (then in Italy), he was educated at a school in Genoa. He became Professor of Astronomy at the University of Bologna (1650), where his determinations of the rotation periods of the planets and his tables of the motions of Jupiter's satellites (1668) brought him fame. In 1669 he became the first director of the new Paris Observatory, where he made a host of observations of Mars, Jupiter and Saturn, and discovered the division of Saturn's rings which still bears his name (1675). He also discovered four satellites of Saturn. One of Cassini's great achievements was his determination of the distance of the planet Mars, and thereby of the distance of the Sun, from observations made simultaneously in Paris and in the French colony of Cayenne.