Tycho Brahe's precise observations, particularly of the comet of 1577 and the supernova of 1572, challenged the prevailing Aristotelian model that posited unchanging heavens and celestial spheres. His data showed that comets and new stars (supernovae) were not atmospheric phenomena, as previously believed, but distant objects that traversed the supposed crystalline spheres, thereby undermining the notion of immutable heavenly spheres.