Galileo Galilei

 Father of modern observational astronomy

Galileo has been called the "father of modern observational astronomy" (among other things). Galileo Galilei once said, "All truths are easy to understand once they are discovered; the point is to discover them" and he spent his life discovering truths.

One of Galileo's contributions to observational astronomy was his discovery of the four largest satellites of Jupiter, which are named the Galilean moons in his honor. He also studied sunspots and analyzed them. His studies of uniformly accelerated motion and the improvements that he made to the telescope are also considered major contributions to scientific and astronomical knowledge. The improvements to the telescope actually led to subsequent astronomical observations.

Aristotle had determined that the earth was at the center of the universe, and the sun revolved around it. Nicolaus Copernicus challenged that theory in the 1530s. Galileo was one of the very few thinkers of the time who adopted the Copernican theory before 1600.

Galileo published an account of his telescopic observations of the moons of Jupiter in 1610. The following year, he visited Rome to demonstrate his findings to philosophers and mathematicians of the Jesuit Collegio Romano to let them see that the four moons of Jupiter were real. Indisputable visual proof, however, was not enough.

The Catholic Church prohibited the advocacy of heliocentrism (a sun-centered universe). Galileo managed to evade the Roman Inquisition for a full year, but he was finally forced to recant his belief in heliocentrism, and he spent the last years of his life under house arrest.