 His observations of the satellites of Jupiter caused a revolution in astronomy : a planet with smaller planets orbiting it did not conform to the principles of Aristotelian cosmology , which held that all heavenly bodies should circle the Earth , and many astronomers and philosophers initially refused to believe that Galileo could have discovered such a thing . His observations were confirmed by the observatory of Christopher Clavius and he received a hero 's welcome when he visited Rome in 1611 . Galileo continued to observe the satellites over the next eighteen months , and by mid @-@ 1611 , he had obtained remarkably accurate estimates for their periods — a feat which Kepler had believed impossible . 
