Poor Simon Marius

Who was Simon Marius? He was a German astronomer who claimed to have discovered Jupiter's four moons a few days before Galileo did. But he didn't publish his findings till 1614. Galileo published his in 1610, the same year he discovered the moons.

So instead of being famous for discovering Jupiter's first four moons, Marius is merely a footnote in history as the man who gave the moons their names -- Io, Europa, Ganymede and Callisto, named after lovers of Jupiter.

This is a portrait of Simon Marius. He sure looks mad, doesn't he?



References:

Galilean Moons
Simon Marius
Marius portrait

Jupiter Moon Dance

The year was 1610. Galileo, working from his home in Padua, Italy, pointed his homemade spyglass at Jupiter. Night after night, he noticed a line of four stars flanking Jupiter. These stars constantly changed position but never strayed far from the planet.

Galileo had discovered that Jupiter, like the Earth, had moons. The widespread belief that everything revolved around the Earth had just been proven wrong.

In this document, you can see the sketches Galileo drew of Jupiter and its moons as observed through his telescope.

Image courtesy of NASA
Today the four moons discovered by Galileo are known as the Galilean moons. In order of distance from Jupiter, they are Io, Europa, Ganymede and Callisto.

Here is a typical view of Jupiter and its moons, similar to what Galileo would have seen. At the time this photo was taken, Io was hiding behind the planet.

Photo courtesy of NASA/JPL/Malin Space Science Systems
References:

Galileo document
The Discovery of the Galilean Satellites
Wikipedia