Answer:
Galileo four key observations are
1. Jupiter has orbiting moons.
2. The Sun has sunspots and rotates on its axis.
3. The Moon has mountains, valleys, and craters.
4. Venus goes through a full set of phases.
Step-by-step explanation:
The above are Galileo's observations that went against the geocentric model and the general beliefs about the universe at the time.
His most critical observation was when he stated that planet Venus is different phases; this observation has a direct impact on the notion that objects orbit the Sun but not the Earth.
He went further to state his observations that the Sun and Moon had surface rough and imperfect surface. This observation disproved the idea that the moon and the Sun had perfect surfaces.
Galileo's observations of Jupiter's orbiting moons showed that there were other centers of motion in the universe.