This thin pamphlet entitled "The Starry Messenger" contains the first
publications of modern observational astronomy, and some of the most important
discoveries to be found in scientific literature. Galileo was the first
astronomer to make full use of the telescope, learning of its invention in the
summer of 1609. He constructed his own, eventually perfecting it to a
magnification of 30 diameters, and began a series of astronomical observations.
He observed the craters of the moon, saw the vast number of stars in the
constellations and Milky Way, and discovered four new "planets," the satellites
of Jupiter. He also declared himself to be a Copernican, and while none of his
work proved that Copernicus's theory of the universe was right, it proved beyond
doubt that the Aristotelian/Ptolemaic world-view was wrong.