SN 1572

After sunset, 11 November 1572

On the evening of 11 November 1572, at Herrevad Abbey in Scania, Tycho Brahe saw an unfamiliar and exceptionally bright star in Cassiopeia.

The traditional biographical account has him distrusting his own eyes and asking servants and passing peasants whether they could see the object too. Once other witnesses confirmed it, he prepared to measure its position against the principal stars of Cassiopeia.

Measuring without a telescope

That sighting began Tycho's systematic record of the object's position, brightness, and colour. One recorded angular separation from Schedir in Cassiopeia is 7° 55′ — taken with naked-eye instruments, decades before the telescope entered astronomy.

His subsequent failure to detect diurnal parallax placed the object beyond the Moon rather than in the changeable terrestrial region, contradicting the Aristotelian claim that the heavens above the Moon do not change.

Five days late to his own discovery

Tycho was not the first to record it. An abbot at Messina and Wolfgang Schüler at Wittenberg both reportedly noted the new star on 6 November, five days earlier, and other observers reported it independently.

His 11 November date follows the Julian calendar he used; Denmark did not adopt the Gregorian calendar until 1700, and the proleptic Gregorian equivalent is 21 November 1572. Modern estimates put the star's maximum apparent visual magnitude at approximately −4.0.

It faded from naked-eye view around March 1574, though sources give dates between February and March because visibility near the limiting magnitude depends on observer and conditions.