Which astronomer published the 1543 model placing the Sun at the center of the known planetary system?

Nicolaus Copernicus published the 1543 model placing the Sun at the center of the known planetary system. His heliocentric model challenged the long-established Ptolemaic system, which placed Earth at the center.

Copernicus presented his ideas in De revolutionibus orbium coelestium, usually translated as On the Revolutions of the Heavenly Spheres. The book appeared in Nuremberg shortly before or around the time of his death on May 24, 1543.

His system was not fully modern: Copernicus still used circular orbits and combinations of circles to reproduce observed planetary motion. Nevertheless, moving the Sun to the central position provided a simpler explanation for phenomena such as the apparent retrograde motion of planets.

Later astronomers refined the model. Johannes Kepler replaced circular orbits with ellipses, Galileo Galilei supplied telescopic observations that supported heliocentrism, and Isaac Newton explained planetary motion through gravitation. Copernicus therefore began a scientific transformation rather than completing it alone.