December 12, 1901] 



NATURE 



133 



THE PHOTOGRAPHS OF NOVA PERSEI. 



REFERENCE has already been made in Nature to 

 the important photographs of the nebula associated 

 with Nova Persei obtained by Mr. Ritchey at the Yerkes 

 Observatory with the 2-foot reflecting telescope, the 

 exposure being four hours. The Astrophysical Journal 



" The amount of motion is almost incredible, being no 

 less than at the rate of ii' per year. The greatest dis- 



t-3^5n;^ 





Fig. I. — The Yerkes Photogr.-iph, September 20. 



for October contains an enlarged (five diameters) copy 

 of the photograph and a diagram made from the original 

 negative, which are now reproduced. 



Still more recently the results secured at the Lick 

 Observatory by Mr. Perrine with the Crossley 3-foot 

 reflector with an e.xposure of more than seven 

 hours, which were telegraphed over in the 

 first instance, have now reached us in some 5 



detail. The communication (Z?«//tV/>/ No. 10) I 



is accompanied by a diagram which shows 

 remarkable changes of position in the more 

 pronounced condensations. This diagram 

 is referred to as follows : — 



" The four masses of nebulosity are 

 designated by the letters a, b, c, d ; the 

 positions which the centres of figure occupied 

 on September 20, as shown in the repro- 

 duction from Mr. Ritchey's photograph, 

 are occupied by the left-hand or north- 

 west end of each of the short lines ; the 

 positions on November 7-8 are occupied 

 by the right-hand or southeast ends of the 

 lines. 



" The line drawn between these positions 

 for each condensation indicates the direction 

 and amount of motion in the interval of 

 forty-eight days. Condensation A is much 

 the best adapted for accurate measurement, 

 from its greater strength and from its forked 

 appearance ; condensations I! and C are not 

 quite so good for measurement as A, but still 

 are very determinate ; but while condens- 

 ation I) is the brightest of all, it is large, and 

 so near the image of the Nova as to make 

 its amount and direction of motion some- 

 what uncertain. 



" It will be seen that the displacements 

 agree well and amount to about li'. The directions are 

 not so consistent and could perhaps be e.xplained by 

 irregular motions in the nebulous mass, by a general trans- 

 lation of the nebula in one direction or by a spiral motion. 

 It is certain, however, that the motion is not radial. 



NO. 1676, VOL. 65] 



-1' -2 'i 



«■ fif 



showing details 



placement (proper motion) in the stellar universe, so far 

 observed, is less than 9" per annum." 



CC CJ ^ ^ 



I I I I 



W 



-I Tf CC CO o 



+ + + + + 





- 6' 



- 4' 



- 2' 



+ 2' 



+ 4' 



+ 6' 



+ 8' 



Fig. 3.- 



Diagram showing changes in position in the condensations as determined by 

 the later observations at the Lick Observatory on November 7-8. 



The note then goes on, " such an exceptional velocity 

 as is here indicated leaves little doubt of the intimate con- 

 nection of this nebulous matter with the Nova and its out- 

 burst. It is, perhaps, too soon to say just what bearing 

 the foregoing observations will have upon the explanation 



