The Copernican System is a model of the solar system proposed by the astronomer Nicolaus Copernicus in the 16th century. It suggests that the Sun is at the center of the universe, and the Earth and other planets orbit around it. This was a significant shift from the earlier Ptolemaic System, which placed the Earth at the center. Copernicus published his ideas in the book titled De revolutionibus orbium coelestium. His heliocentric theory laid the groundwork for modern astronomy and challenged long-held beliefs about the cosmos. This model eventually led to further discoveries by astronomers like Galileo Galilei and Johannes Kepler.