Sidera Lodoicea Explained

Sidera Lodoicea is the name given by the astronomer Giovanni Domenico Cassini to the four moons of Saturn discovered by him in the years 1671, 1672, and 1684 and published in his Découverte de deux nouvelles planètes autour de Saturne in 1673 and in the Journal des sçavans in 1686. These satellites are today known by the following names, given in 1847:

• Iapetus or Saturn VIII, discovered October 25, 1671
• Rhea or Saturn V, discovered December 23, 1672
• Tethys or Saturn III, discovered March 21, 1684
• Dione or Saturn IV, discovered March 21, 1684

The name Sidera Lodoicea means "Louisian Stars", from Latin sidus "star" and Lodoiceus, a nonce adjective coined from Lodoicus, one of several Latin forms of the French name Louis (reflecting an older form, Lodhuwig). Cassini intended the name to honor King Louis XIV of France, who reigned from 1643 to 1715, and who was Cassini's benefactor as patron of the Paris Observatory, of which Cassini was the director.

The name was modelled on Sidera Medicea, "Medicean stars", the Latin name used by Galileo to name the four Galilean satellites of Jupiter, in honor of the Florentine house of Medici.

The following contemporary (1686) notice records Cassini's choice of name, and explains his rationale for the same:

References

• 10.1098/rstl.1686.0013. Cassini . G. D.. Giovanni Domenico Cassini. 1686–1692. An Extract of the Journal Des Scavans. Of April 22 st. N. 1686. Giving an Account of Two New Satellites of Saturn, Discovered Lately by Mr. Cassini at the Royal Observatory at Paris. Philosophical Transactions of the Royal Society of London. 16. 179–191. 79–85. 101844. 186210940 .