NiJW STARS. 153 



diminish, and the star gradually reset ibled Jupiter ; hut by 

 January, 1573, it had become less bright than that planet. 

 Successive photometric estimates gave the following results : 

 for February and March, equality with stars of the first mag- 

 nitude (stellarum affixarum primi honoris for Tycho Brahe 

 seems to have disliked using Manilius's expression of stelhe 

 fixae) ; for April and May, with stars of the second magni- 

 tude ; for July and August, with those of the third ; for Oc- 

 tober and November, those of the fourth magnitude. To- 

 ward the month of November, the new star was not bright- 

 er than the eleventh in the lower part of Cassiopeia's chair. 

 The transition to the fifth and sixth magnitude took place 

 between December, 1573, and February, 1574. In the fol- 

 lowing month the new star disappeared, and, after having 

 shone seventeen months, was no longer discernible to the 

 naked eye." (The telescope was not invented until thirty 

 seven years afterward.) 



The gradual diminution of the star's luminosity was, more- 

 over, invariably regular ; it was not (as is the case in the 

 present day with r\ Argus, though indeed that is not to be 

 called a new star) interrupted by several periods of rekind- 

 ling or by increased intensity of light. Its color also changed 

 with its brightness (a fact which subsequently gave rise to 

 many erroneous conclusions as to the velocity of colored rays 

 in their passage through space). At its first appearance, as 

 long as it had the brilliancy of Venus and Jupiter, it was 

 for two months white, and then it passed through yellow 

 into red. In the spring of 1573, Tycho Brahe compared it 

 to Mars ; afterward he thought that it nearly resembled Be- 

 telgeux, the star in the right shoulder of Orion. Its color, 

 for the most part, was like the red tint of Aldebaran. In 

 the spring of 1573, and especially in May, its white color re- 

 turned (albedinem quandam sublividam induebat, qualis Sa- 

 turni stellee subesse videtur). So it remained in January, 

 1574 ; being, up to the time of its entire disappearance in 

 the month of March, 1574, of the fifth magnitude, and white, 

 but of a duller whiteness, and exhibiting a remarkably strong 

 scintillation in proportion to its faintness. 



The circumstantial minuteness of these statements* is of 



* De admiranda Nova Stella, anno 1572, exorla in Tychonis Brahe 

 Astronomia, instauratm Progymnasmata, 1603, p. 298-304, and 578. In 

 the text I have closely followed the account which Tycho Brahe him- 

 self gives. The very doubtful statement (which is, however, repeated 

 in several astronomical treatises) that his attention was first called to 



