Which ancient Greek astronomer is known for an early Sun-centered model of the cosmos?

The ancient Greek astronomer known for an early Sun-centered model of the cosmos was Aristarchus of Samos.

Aristarchus lived in the third century BCE and is generally credited with the first known fully heliocentric model. His original work on the Sun-centered cosmos has been lost, but Archimedes described its central ideas: the Sun and fixed stars remained stationary, while Earth revolved around the Sun and rotated on its axis.

Aristarchus reached this view partly through measurements of the Sun and Moon. He recognized that the Sun was much larger than Earth and reasoned that the larger body was a more natural center for the system. He also proposed that the stars were extremely distant, helping explain why Earth’s motion did not produce an obvious change in their apparent positions.

His model was not widely adopted in antiquity. Aristotle’s Earth-centered ideas and, later, Ptolemy’s geocentric system dominated astronomical thought for centuries. Copernicus revived heliocentric astronomy in the sixteenth century, but Aristarchus deserves the distinction of being its earliest known ancient Greek advocate. Eratosthenes, Eudoxus, and Hipparchus made important contributions to astronomy, but they are not the canonical answer to this question.