The Copernican Revolution:

The Copernican model consisted of  the Sun at the centre with  the six planets, Mercury, Venus, the Earth with the Moon-round  it, Mars, Jupiter and Saturn going round  it in circular orbits. In this model too the stars formed a fixed sphere in  the background. Copernicus also believed  all planets to be of the same size. His model worked as well as Ptolemy's spheres in explaining the apparent motion of  the planets. But it led to a confrontation with the adherents of geocentric model.  It was not generally accepted until much later when Galilee's and Kepler's works proved  that the heliocentric model was valid. 

Fig: Copernican system 

The sun-centred model of Copernicus was established by  the astronomical observations of Galileo Galilei when  in  1609, he turned his small, imperfect telescope towards the sky. In the first few nights of observs:ion  of  the heavens, Galileo saw enough to shatter the ancient picture of the serene, perfect, harmonious world.