On 11 November 1572, Tycho observed (from Herrevad Abbey) a very bright star, now numbered SN 1572, which had unexpectedly appeared in the constellation Cassiopeia. Because it had been maintained since antiquity that the world beyond the Moon's orbit was eternally unchangeable (celestial immutability was a fundamental axiom of the Aristotelian world-view), other observers held that the phenomenon was something in the terrestrial sphere below the Moon. However, Tycho observed that the object showed no daily parallax against the background of the fixed stars. This implied that it was at least farther away than the Moon and those planets that do show such parallax. He also found that the object did not change its position relative to the fixed stars over several months, as all planets did in their periodic orbital motions, even the outer planets, for which no daily parallax was detectable. This suggested that it was not even a planet, but a fixed star in the stellar sphere beyond all the planets. In 1573, he published a small book "De nova stella", thereby coining the term nova for a "new" star (we now classify this star as a supernova and know that it is 7500 light-years from Earth). This discovery was decisive for his choice of astronomy as a profession. Tycho was strongly critical of those who dismissed the implications of the astronomical appearance, writing in the preface to "De nova stella": ""O crassa ingenia. O caecos coeli spectatores"" ("Oh thick wits. Oh blind watchers of the sky"). The publication of his discovery made him a well-known name among scientists across Europe.