* Phases of Venus: Galileo's observations of Venus showed that it went through phases similar to the Moon, ranging from a crescent to a full disk. This could only be explained if Venus orbits the Sun, not the Earth. If Venus orbited the Earth, we would always see a similar face, like we do with the Moon.
* Sunspots: While not directly confirming heliocentricity, the discovery of sunspots demonstrated that the Sun was not perfect and unchanging, as was believed by the prevailing geocentric model (Earth-centered universe). This challenged the idea that the Sun was a divine and flawless body, further weakening the geocentric argument.
These discoveries were crucial in challenging the long-held geocentric model and providing strong evidence in support of Copernicus' heliocentric theory.
