IO

La première observation connue d'Io est réalisée par Galilée le 7 janvier 1610. La découverte d'Io et des autres satellites galiléens est publiée par l'astronome dans son ouvrage Sidereus Nuncius en mars 1610. En 1614, dans son Mundus Jovialis, Simon Marius prétend avoir découvert ces objets en 1609, une semaine avant Galilée. Quelle que soit la validité des propos de Marius (Galilée, par exemple, le considère comme un imposteur et un plagiaire), Galilée est considéré comme le découvreur d'Io, ayant publié cette découverte le premier.

Simon Marius (Latinized from German Simon Mayr; January 20, 1573 – January 5, 1625) was a German astronomer. He was born in Gunzenhausen, near Nuremberg, but he spent most of his life in the city of Ansbach.

In 1614 Marius published his work Mundus Iovialis describing the planet Jupiter and its moons. Here he claimed to have discovered the planet's four major moons some days before Galileo Galilei. This led to a dispute with Galileo, who in Il Saggiatore in 1623 accused Marius of plagiarism. But a jury in The Netherlands in 2003 examined the evidence extensively and ruled in favor of Marius's independent discoveries, with results published by Bosscha in 1907. Apparently Marius discovered the moons independently, but started keeping notes one day later than Galileo, when Marius's date in the Julian calendar is increased by 10 days to convert to the Gregorian calendar used by Galileo.^[1]

Regardless of priority, the mythological names by which these satellites are known today (Io, Europa, Ganymedeand Callisto) are those given them by Marius:^[2]

Io, Europa, Ganimedes puer, atque Calisto

lascivo nimium perplacuere Iovi.

Io, Europa, the boy Ganymede, and Callisto greatly pleased lustful Jupiter.

Rehabilitating Simon Marius

Io was one of Zeus's many lovers