The heliocentric model is an astronomical theory that places the Sun at the center of the solar system, with the Earth and other planets orbiting around it. This model was first proposed by the ancient Greek philosopher Aristarchus of Samos but gained prominence in the 16th century through the work of Nicolaus Copernicus. The heliocentric model challenged the earlier geocentric model, which positioned the Earth at the center of the universe. The acceptance of the heliocentric model was crucial for the advancement of modern astronomy, leading to significant discoveries by astronomers like Galileo Galilei and Johannes Kepler.