When did aristarchus of samos propose his heliocentric model?

The word "helios" in Greek means "sun." Heliocentric means that the sun is at the center. A heliocentric system is one in which the planets revolve around a fixed sun.

Aristarchus of Samos proposed the heliocentric model in 200 Bc. It was not accepted at that time because people believed in the geocentric model and believed that the earth was the center of the universe.