B88) 7 
XLV. 
THE NEBULA SURROUNDING NOVA PERSEI. 
By W. HE. WILSON, E.RB.5. 
[Read January 22; Received for Publication, Fepruary 12; 
Published Aprit 14, 1902.] 
On the 22nd of last February a new star of the lst magnitude 
was detected in the constellation Persei almost simultaneously by 
Dr. Anderson, of Edinburgh, and Mr. Hllard Gore, of Dublin. 
The outburst seems to have been exceedingly sudden, as that 
particular region of the sky was photographed in America on 
February 19th, only three days before, and there is not a trace 
of the star. The plate was given an exposure of over one hour, 
so that stars as faint as the 11th magnitude are clearly depicted 
on it. 
The new star seems to have attained its maximum brillianey a 
few days after its discovery, when it outshone stars of the Ist 
magnitude. It then rapidly waned, and, with some curious 
fluctuations in brilliancy, is now of about the 7th magnitude. 
_ In September last, Mr. Ritchey, at the Yerkes Observatory, 
took a photograph of the Nova, using a reflecting telescope of two 
feet aperture, and giving the plate an exposure of about 4 hours. 
He thus found that the Nova was surrounded by a spiral nebula. 
This was an interesting discovery, as there is some suspicion that 
these new stars are connected in some way with nebula. 
On November 9th and 13th Ritchey again photographed the 
Nova, giving his plates an exposure of about 7 hours. When 
these photographs were compared with the one of September 20th 
it was found that the nebula had altered in shape, and expanded 
in size. This was a most startling discovery, and quite unique in 
astronomical annals. The only possible explanation seemed to be 
that the nebula was the result of some terrific explosion of which 
the Nova was the origin, and that it was in fact expanding in 
volume like smoke after it leaves the mouth of a cannon. But it 
