A theory of planetary motions, proposed by Copernicus, according to which all planets move in circular orbits around the Sun, the ones closer to the Sun moving faster, with the Earth itself a planet orbiting between Venus and Mars.
Heliocentric version of the Solar System, developed by Copernicus in the 16th Century AD, though anticipated by some ancient Greek thinkers, including Pythagoras (6th Century BC) and even earlier by Indian Vedic texts, notably Yajnavalka's Satapatha Brahmana (8th Century BC) which may have influenced him. This system eventually replaced the geocentric system formalised by Ptolemy in the 2nd Century AD, even though it was less accurate, at least until advances in planetary motion discovered by Kepler in the 17th Century. Although Kepler was also a marvellous and dedicated astrologer, this marked the beginning of the current alienation of astrology from astronomy. Since astrology is primarily concerned with the effect the planetary forces have upon the beings that inhabit the Earth, most astrologers still favour the geocentric system, at least for astrological calculations.
The system proposed (in 1543) by Nicholas Copernicus in which the Sun is the central body, with the Earth and the other bodies moving around it. This model superseded the Ptolemaic system which had persisted for nearly 2000 years. Copernicus' idea was not new, it had been proposed in about 300 BC by Aristarchus of Samos, a Greek philosopher. Both astronomers have Lunar craters named after them.