Giovanni Domenico Cassini was born on June 8, 1625 in Perinaldo, near Nice, and died on 14 September 1712 in Paris.

In 1671 he became director of the Paris Observatory. He determined the rotation period of Jupiter and Mars and discovered four Saturnian satellites (Lapetus in 1671, Rhea in 1672, and both Tethys and Dione in 1684). In 1675 he discovered the gap in the ring system of Saturn, now known as the Cassini Division.