Cassini, Giovanni Domenico

(Jean Dominique Cas-sini). Born June 8, 1625, in Perinaldo; died Sept. 14, 1712, in Paris. Astronomer. An Italian by birth. Member of the Paris Academy of Sciences (1669). Director of the Paris Observatory (from 1669).

Cassini discovered the rotation of Jupiter (1665) and Mars (1666), four new satillites of Saturn (1671–84), and the division of Saturn’s rings into an inner ring and an outer ring by a dark gap (the Cassini division). He also investigated the optical liberation of the moon. Cassini made the first reliable determination of the sun’s parallax from joint observations of Mars with the French astronomer J. Richer (9.5“-10.0”; modern value, 8.8”).