The mathematical contemplation by the Dane Tycho Brahe over the new and never before observed star, Copenhagen 1573 (the title in abbrevation) is a small book demonstrating Tycho's scientific method, but also how he is influenced by the contemporary Aristotelian views. He thoroughly measures the position of the new object relative to the surrounding fixed stars, relative to the ecliptic, and relative to the celestial equator. He can state that these values didn't change for half a year, at least not within what is measurable. Hence, the object cannot be attached to any of the seven planetary spheres, since the object, 36 degrees from the pole of the ecliptic, in that case should have followed the motion of this sphere relative to the fixed stars, after half a year also observably for the sphere of Saturn. He also proves, that the object shows no parallax relative to the fixed stars between zenith and the horizon, which it should do if it were sublunary (since the spheres are moving with the centre of earth as centre, while the observer on the surface of earth is the radius of earth from the centre). From this can be concluded, according to Tycho, that the object is not a meteor or comet (sublunary phenomena in the Aristotelian view), i.e. the object must be attached to the "eighth" sphere, i.e. be a star. In the Aristotelian world, in which the young Tycho certainly is living, there can be no new stars, and therefore the new star must be an unexplicable miracle, that only could be understood astrologically, i.e. as a sign of God. To Tycho's knowledge, Hipparchus had observed a new star as described by Pliny, but that was 1700 years before Tycho's time! Tycho is therefore (at this occasion) explicitly turning down the possibility of physically explaining how the star has come into existence, it's just a too rare event, instead he ends the book with an astrological analysis of the consequencies of the phenomenon as an omen. Later Tycho wrote a larger book about the Nova 1572 with partly new information and new ideas.

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Lund Observatory, Box 43, SE-221 00 Lund, Sweden Visiting address: Sölvegatan 27 Phone: +46 46 22 27300, Fax: +46 46 22 24614 Publisher: Leif Lönblad E-mail: webmaster@astro.lu.se Last updated: 2002, March 19