Benchmark 10A
Historical Perspectives: Displacing the Earth from the Center of the Universe
Grades 9-12, page 241

Johannes Kepler, a German astronomer who lived at about the same time as Galileo, showed mathematically that Copernicus' idea of a sun-centered system worked well if uniform circular motion was replaced with uneven (but predictable) motion along off-center ellipses.

See Content Standard G History and Nature of Science (grades 9-12): Historical Perspectives.