1-152-589 - Ann Ronan Picture Library/Heritage-Images

Galileo's observation of the star cluster in Orion and of the Praesepe cluster, 1610. Galileo Galilei (1564-1642), one of the greatest scientists of all time, discovered Jupiter's moons and the laws governing falling bodies. This illustration was published in his Sidereus Nuncius (The Sidereal Messenger), 1610. The book was the first work describing what could be seen in the night sky with the newly invented telescope. Using a telescope of his own design, Galileo observed that the planet Jupiter had four satellites, that orbited the planet in a predictable manner like Earth's Moon.