Simon Marius (January 10, 1573 – December 26, 1624) was a German astronomer

Astronomer

An astronomer is a scientist who studies celestial bodies such as planets, stars and galaxies.Historically, astronomy was more concerned with the classification and description of phenomena in the sky, while astrophysics attempted to explain these phenomena and the differences between them using...

. He was born in Gunzenhausen

Gunzenhausen

Gunzenhausen is a town in the Weißenburg-Gunzenhausen district, in Bavaria, Germany. It is situated on the river Altmühl, 19 km northwest of Weißenburg in Bayern, and 45 km southwest of Nuremberg. Gunzenhausen is a nationally recognized recreation area. The city was mentioned first in the...

, near Nuremberg

Nuremberg

Nuremberg[p] is a city in the German state of Bavaria, in the administrative region of Middle Franconia. Situated on the Pegnitz river and the Rhine–Main–Danube Canal, it is located about north of Munich and is Franconia's largest city. The population is 505,664...

, but he spent most of his life in the city of Ansbach

Ansbach

Ansbach, originally Onolzbach, is a town in Bavaria, Germany. It is the capital of the administrative region of Middle Franconia. Ansbach is situated southwest of Nuremberg and north of Munich, on the Fränkische Rezat, a tributary of the Main river. As of 2004, its population was 40,723.Ansbach...

.

In 1614 Marius published his work Mundus Iovialis describing the planet Jupiter

Jupiter

Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...

 and its moons. Here he claimed to have discovered the planet's four major moons some days before Galileo Galilei

Galileo Galilei

Galileo Galilei , was an Italian physicist, mathematician, astronomer, and philosopher who played a major role in the Scientific Revolution. His achievements include improvements to the telescope and consequent astronomical observations and support for Copernicanism...

. 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.