Background

The Italian physician and astronomist Galileo Galilei, son of the mathematician Vicenzo Galilei, was born in Pisa (Italy). His contributions to the astronomy are in particular the observations he did and the clear description of them.

In January 1610 Galileo discovered moons around other planets then Earth. When he looked at Jupiter through his telescope, he saw four little lightdots, these were four of the Jupiter moons, at present better known as Io, Ganymedes, Europa, and Callisto. These four moons together are named the Galilean. Galileo described far beyond the planets 36 stars in the Plejads, of which only a few can be observed without special means.

Furthermore he discovered 40 stars in the Praesepe cluster, which in his days where assumed to be only 3 nebulae stars.Through his telescope he found out that the Milky Way consists of many seperate stars. Several ideas of Galileo, by which he rejected the ideas of Ptolomy and Aristote, encountered opposition of the mighty Roman-Catholic Church and scientists. He was even forced to proclaim that his statements of the Earth not being the center of the Universe, where only 'vague assumptions' in stead of facts.

In 1623 he published the book Il Saggiatore in which he wrote about the Copernican system. In 1632 he came with his boek Dialogo sopra i due massimi sistemi del Mondo, Tolemaicoe Copernicano. In this book he described that the Copernican system was not that bad at all. In 1638 became completely blind. Many people say that this is caused by his observations of the Sun, without protection of his eyes. Galileo Galilei died on January 8, 1642 and is buried on Santa Croce in Florence.