His most famous discovery came in June or July of 1609, when he had learned that the Dutchman Hans Lippershey and several others had taken magnifying glasses and constructed the first working telescope. Without knowing the technical details of the construction of the device, he was able to design and create one for himself, and he is credited in being the first to train the new device towards the heavens. Over time he continued to upgrade it. He found mountains on the Moon, viewed [[Venus]] and [[Jupiter]], and with some protection located [[sunspots]].
In 1610 [[Galileo]] while observing [[Jupiter]] he discovered four smaller bodies (now called - the [[Galilean moons]] of Io, Europa, Ganymede, Callisto) - revolving around it, which eventually became one of Galileo's most well-known and important discoveries: [[heliocentrism]]. Galileo's two main evidences in this respect both came from the ability of his telescope to carefully examine the heavens, and his observations of Jupiter and Venus provided strong evidence against [[geocentrism]] (at the time this doctrine was not simply limited to the earth's being the center of the universe, but also that no extraterrestrial orbits existed). <ref> David Filkin, "Stephen Hawking's Universe", David Filkin Enterprises Limited, 1997, pg.44 - 46</ref>
[[NASA]] scientist Ron Baalke wrote