206 COSMOS. 



strongly than stars of the first magnitude. Its brightness 

 was greater than that of Sirius, a Lyrae, or Jupiter. Foi 

 splendour, it was only comparable to Venus when nearest 

 to the earth (that is, when only a quarter of her disc is illu- 

 minated). Those gifted with keen sight could, when the air 

 was clear, discern the new star in the day-time, and even at 

 noon. At night, when the sky was overcast, so that all 

 other stars were hidden, it was often visible through the clouds, 

 if they were not very dense (nubes non admodum densas). 

 Its distances from the nearest stars of Cassiopeia, which 

 throughout the whole of the following year I measured with 

 great care, convinced me of its perfect immobility. Al- 

 ready, in December, 1572, its brilliancy began to diminish, 

 and the star gradually resembled Jupiter ; but by January, 

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

 photometric estimates gave the following results : for Febru- 

 ary and March, equality with stars of the first magnitude 

 (stellarum affixarum primi honoris for Tycho Brahe seems to 

 have disliked using Manilius's expression of stellse fixae) ; for 

 April and May, with stars of the second magnitude ; for July 

 and August, with those of the third ; for October and November, 

 those of the fourth magnitude. Towards the month of No- 

 vember, the new star was not brighter 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 following 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 afterwards.) 



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

 over invariably regular; it was pot (as is the case in the 

 present day with 77 Argus, though indeed that is not to be 

 called a new star) interrupted by several periods of re-kindling 

 or by increased intensity of light. Its colour also changed with 



