* Nicolaus Copernicus (1473-1543): He is best known for proposing the heliocentric model of the solar system, which placed the Sun at the center, rather than the Earth. This revolutionary theory challenged the long-held geocentric model (Earth-centered) and had a profound impact on our understanding of the universe.

* Tycho Brahe (1546-1601): While he didn't fully embrace the heliocentric model, Brahe was a brilliant observer and collected vast amounts of precise data on the positions of planets and stars. His detailed observations, particularly of Mars, proved crucial for Johannes Kepler's later development of his laws of planetary motion.

These two astronomers, along with Johannes Kepler and Galileo Galilei, played a crucial role in the scientific revolution of the Renaissance.