Heliocentric model, published by Nicolaus Copernicus (1473-1543) in 1543 in his book De revolutionibus orbium coelestium (On the Revolutions of the Heavenly Spheres). This Sun-centred model revolutionised astronomy, replacing the previous Earth-centred (geocentric) model. The diagram (labelled in Latin), shows concentric spheres around the Sun (centre). The outer, fixed sphere (I, the stars) surrounds rotating spheres (II-VII) for Saturn, Jupiter, Mars, Earth (and the Moon), Venus, and Mercury. Some of the planets have their orbital periods labelled. This model still used the heavenly spheres of the Ancient Greeks. Later work showed that the stars were much further away and that planetary orbits are ellipses, not circles.