Heliocentric

Tycho Brahe's geo-heliocentric system (c. 1587)

Prior to the publication of De Revolutionibus, the most widely accepted system had been proposed by Ptolemy, in which Earth was the center of the universe and all celestial bodies orbited it. Tycho Brahe (1546–1601), arguably the most accomplished astronomer of his time, advocated against Copernicus' heliocentric system and for an alternative to the Ptolemaic geocentric system: a geo-heliocentric system now known as the Tychonic system in which the Sun and Moon orbit Earth, Mercury and Venus orbit the Sun inside the Sun's orbit of Earth, and Mars, Jupiter and Saturn orbit the Sun outside the Sun's orbit of Earth.