|Right Ascension|| 00 : 25.3 (h:m)
|Declination|| +64 : 09 (deg:m)
|Distance|| 10,000 (ly)
|Visual brightness|| -4 (mag)
When Tycho Brahe was on his way home on November 11, 1572, his attention was attracted by a star in Cassiopeia which was shining at about the brightness of Jupiter and which had not been seen in this place before. Tycho reports (from Burnham's Celestial Handbook):
``On the 11th day of November in the evening after sunset, I was contemplating the stars in a clear sky. I noticed that a new and unusual star, surpassing the other stars in brilliancy, was shining almost directly above my head; and since I had, from boyhood, known all the stars of the heavens perfectly, it was quite evident to me that there had never been any star in that place of the sky, even the smallest, to say nothing of a star so conspicuous and bright as this. I wqs so astonished of this sight that I was not ashamed to doubt the trustworthyness of my own eyes. But when I observed that others, on having the place pointed out to them, could see that there was really a star there, I had no further doubts. A miracle indeed, one that has never been prevoiously seen before our time, in any age since the beginning of the world.''
Tycho was so impressed by this event that he devoted the rest of his professional life to astronomy only. Nevertheless, Tycho had not been the first to discover this "new" star; according to Burnham, it was probably first seen by W. Schuler on November 6, 1572. Tycho found it at about as brilliant as Jupiter, and it became soon equal to Venus. For about two weeks the star could be seen in daylight. At the end of November it began to fade and change color, from bright white over yellow and orange to faint reddish light, finally fading away from visibility in March, 1574, having been visible to the naked eye for about 16 months.
The image in this page is from Tycho Brahe's "Stella Nova", taken from the online edition at the Danish National Library of Science and Medicine.
The remnant of this supernova had to wait for its discovery until the 1960s, when extremely faint nebulosity was identified on Mt. Palomar photo plates near the position, and gaseous remainders were identified by their radio emission; a stellar remnant has not been found. The radio source has been cataloged as 3C 10, the SNR as G 120.1+1.4 in Dave Green's catalogue of galactic SNRs. The gas shell is now expanding at about 9000 km/s (compare with the Crab Nebula's about 1000 only), and has reached an apparent diameter of 3.7 arc minutes. Tycho's supernova remnant appears to be the more typical representative of these class of objects of the two.