Italian astronomer and physicist Galileo Galilei first used the telescope astronomically in 1609. He was the first to see such wonders as sunspots, which he described as blemishes on the Sun, and features on the Moon like Mare —seas or bodies of water.
Galileo’s observations of the planets were monumental.
- Mercury and Venus showed phases , which meant Mercury and Venus orbits the Sun between Earth and the Sun
- Four bright moons around Jupiter
- Galileo’s continued observation of Jupiter’s moons was important in the Geocentric-Heliocentric Solar System debate.
- Milky Way and found it had countless stars
An interesting note about Galileo…
Galileo also worked on several problems in physics, in addition to his pioneering astronomical observations. He was a deeply religious man, as his daughter who was a nun. Galileo was held on house arrest by the Church and made to recant his theory of a Heliocentric Sun-centered Solar System. Galileo’s right hand middle finger was removed after his death and is on display in the Science Museum of Florence, along with some of his telescopes.