In 1608, Galileo Galilei is credited as the first to turn his
telescope to the heavens.
He soon discovered craters on our
Moon, sun
spots, the moons of Jupiter, and that Venus has phases like our Moon.
Galileo claimed that his
observations only made sense if all the planets revolved around the Sun (as proposed by Aristarchus and Copernicus) rather than the Earth.
Galileo
Galilei
1564 - 1642
Historical Background of Spectroscopy
The Inquisition eventually
forced Galileo to publicly
recant this conclusion.