RECENT PROGRESS IN ASTROPHYSICS. 
BY 
John George Hagen, S. J. 
[Read before the Society February 3, 1900.] 
The recent progress in astrophysics is so extensive that 
only a few of the most important works and discoveries can 
be mentioned in this report. We have chosen the following 
three subjects: 
1. The Cluster-type of Variable Stars .—The discovery by 
Professor Bailey of a great number of variable stars in cer¬ 
tain clusters has been known for some years. In Chandler’s 
III. Catalogue seven clusters of this kind are mentioned, five 
of which are visible in our latitudes. 
The most remarkable of these clusters is the one desig¬ 
nated as Messier 5, or N. G. C. 5904, on account of the great 
uniformity of the light variations. The photographs of this 
cluster, which were taken with the 13-inch Boyden refractor 
at the Arequipa station, show about 900 stars. Of these stars 
63 have so far been recognized as variables from nearly 100 
plates, and 40 of these variables have been accurately deter¬ 
mined with regard to period and range of variability. With 
the exception of two of them, whose periods are about one 
month, they all show an unexpected uniformity in the time 
and range of their variation and in the shape of their light- 
curve. Their mean period is about half a day, or, more ex¬ 
actly, 0 d .526 — 12 h 37 m .4, with a mean deviation of 0 d .047 = 
l h 7 m .7, the greatest deviation being only 2 h 21 m .l. The max¬ 
imum brightness of these variables is between 13 M .4 and 
13 M .9, and the minimum brightness between 14 M .5 and 14 M .9, 
with a meau range of 1 M .1 ? between 13 M ? 6 and 14 M .7. The 
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