100 BARNARD— SOME PECULIARITIES OF THE NOV^. 



know something of the visual history of Nova Coronse BoreaHs of 

 1866, for it was observed at Bonn, previous to its outburst, as BD -|- 

 26° 2765 of the 9.5 magnitude. Though this star appeared some dis- 

 tance from the Milky Way (in which the novse apparently belong), 

 there is no other reason to question its character as a nova. 



There is now some evidence that possibly the novse were all vari- 

 able stars in the earlier stages of their history, but the proof is not 

 conclusive. Photography has shown that at least two of these stars 

 were small variables before they became novee. Nova Persei is the 

 best example. Thanks to the splendid collection of stellar photo- 

 graphs of the Harvard College Observatory extending over more 

 than a third of a century, we know that previous to its sudden appear- 

 ance in 1 90 1, when it became brighter than the first magnitude, Nova 

 Persei was a small variable star of about 14th magnitude. After its 

 outburst in 1901 it slowly faded to its original brightness and again 

 became a small variable star — varying perhaps just as it did before 

 the blaze-up. Apparently the great outburst was only an interruption 

 in its regular variability, which is now past and forgotten. 



The other. Nova Aquilae of 1918, which became brighter than 

 any star in the sky with the exception of Sirius and perhaps Canopus, 

 previous to June 8 was also a small variable star of 10.5 magnitude. 

 It has not yet sunk to its original faintness, certainly not from a 

 photographic standpoint, though it has nearly done so. It is only by 

 comparing the present photographs of it with the early ones that we 

 can tell when this event occurs. It will probably resume its vari- 

 ability later on. Of course, these statements of variability have noth- 

 ing to do with the peculiar fluctuations of the light of a nova in its 

 immediate decline from its maximum. 



As we have said, it would appear that the outburst in these two 

 stars was only an interruption in their variability. Professor Turner 

 has made an attempt to connect up the present variability of Nova 

 Persei with that before the great change occurred, but he has not yet 

 obtained a satisfactory result. 



Perhaps the phenomena of Nova Aquilas were of even greater 

 interest than those of Nova Persei. This was probably due to the 

 extremely great brilliancy of the star at its maximum. Its entire 



