Simon Marius

Astronomer, born in Gunzenhausen, SC Germany. A pupil of Tycho Brahe, in 1609 he claimed to have discovered the four satellites of Jupiter independently of Galileo. He named them Io, Europa, Ganymede, and Callisto, but other astronomers merely numbered them, as they did not recognize his claim to discovery. He was one of the earliest users of a telescope, and the first to observe by this means the Andromeda nebula (1612).

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. This led to a dispute with Galileo, who showed that Marius provided only one observation as early as Galileo's, and it matched Galileo's diagram for the same date, as published in 1610. It is considered possible that Marius discovered the moons independently, but at least some days later than Galileo; if so, he is the only person known to have observed the moons in the period before Galileo published his observations.

Simon Marius also claimed to be the discoverer of the Andromeda "nebulae", which had in fact already been known to Arab astronomers of the Middle Ages.