These discovers where made through his own astronomical telescope in which he studied and observed the universe. Galileo pointed his telescope at the sun and noticed many dark spots on it. These dark sun spots contracted the current notion of that time that the sun was a perfect unblemished sphere (2009, p. 610). He observed these spots and tracked their movements, which he estimated moved in just under a month. Galileo used this observation to support the notion that the sun has rotational movement, and helped to show that if the sun rotated then the Earth could also (Chew, 2012).
Galileo then pointed his telescope at Venus and noticed that Venus had phases similar to the moon. These moon-like phases confirmed that Venus was moving around the sun, and was a convincing demonstration of the heliocentric solar system. In the Ptolemaic system where Earth was the center of the Universe, you wouldn’t be able to see different phases, just the crescent phase. Since, Venus would always lie between the sun and the Earth (Chew, 2012).
Galileo also observed Jupiter over several consecutive nights revealing four star-like objects. The objects moved from night to night, sometimes even disappearing behind or in front of the Jupiter. Galileo correctly inferred that these star-objects where the moons of Jupiter, and their orbit was similar to the moon and Earth’s (Zax, 2009). This was the first time, heavenly bodies had been observed orbiting another planet, and confirmed that not everything was orbiting around Earth. If Jupiter can move through space and not leave its moon behind then the Earth could then move without causing the moon to be left behind or flung out into the Universe (Galileo, 2010). These observations Galileo made strengthened the heliocentric theory.
When Galileo studied the…