What celestial body did Galileo observe, leading to evidence that supported the heliocentric model?

Galileo Galilei observed several celestial bodies that supported the heliocentric model. Here are the steps he took:

1. Observation of the Moon: Galileo was the first to point a telescope towards the sky. He observed that, contrary to the popular belief of the time, the Moon was not a perfect sphere but had craters and mountains. This contradicted the Aristotelian belief in the perfection of the heavens.

2. Discovery of Jupiter's Moons: In 1610, Galileo discovered four moons orbiting Jupiter. This was significant because it was the first time anyone had observed a celestial body orbiting something other than the Earth. This provided direct evidence against the geocentric model, which held that all celestial bodies revolve around the Earth.

3. Observation of Venus Phases: Galileo also observed the phases of Venus, which could only be explained if Venus was orbiting the Sun, not the Earth. This was another strong evidence in favor of the heliocentric model.

4. Observation of Sunspots: Galileo observed that there were dark spots on the Sun that moved over time. This suggested that the Sun was rotating on its axis, which was more consistent with the heliocentric model.

These observations by Galileo provided strong evidence for the heliocentric model, where the Sun, not the Earth, is at the center of the solar system.