534 
ASTRONOMY: R. G. AITKEN 
elusion, in 1910,^ based on an analysis of the spectral classification of 164 
of the more rapidly moving binary stars on my observing program. 
The ten stars of Classes M and Oe5 are obviously exceptional, and 
the number is too small for any discussion of value. The following 
points however may be noted: The stars are all bright; the proper 
motions are very small; orbital motion has been observed in only one of 
them (r? Geminorum), and in this system it is very slow; the companion 
in each instance is much fainter than its primary, and the angular 
separation between the components is neither very small nor very large. 
Probably they are all very distant. 
TABLE IV 
Spectral Classification of Double Stars 
SPECTRAL CLASS 
B 
A 
F 
G 
K 
M 
OeS 
I 
0 
8 
4 
2 
3 
II 
2 
19 
14 
5 
12 
Ill 
3 
37 
59 
28 
22 
IV 
18 
81 
68 
45 
26 
1 
V 
47 
101 
54 
31 
24 
5 
2 
VI 
9 
84 
47 
31 
15 
1 
1 
VII 
3 
19 
33 
16 
14 
VIII 
1 
8 
29 
16 
8 
Total 
83 
357 
308 
174 
124 
7 
3 
The percentage of very close double stars — under 0''.50 — is consider- 
ably greater in Classes B, A and F than in Classes G and K, but the 
percentage of pairs over 2" X) is about the same in all classes except K, 
in which it is larger. To discuss the correlation between angular sepa- 
ration and spectral class we need further data. I hope to take up this 
question and others in a later paper. 
The conclusions here presented of course apply only to the data upon 
which they rest, and, in view of the many warnings we have had against 
basing 'laws of nature' upon incomplete statistics, I refrain from any 
comment upon the bearing they may have upon current theories of the 
evolution of double star systems. It is my opinion that we have not 
yet sufficient knowledge of the facts to establish any theory with reason- 
able certainty. 
1 "On Double Stars," R. G. Aitken, San Francisco, Pub. Astr. Soc. Pac, 16, 235 (1904). 
2 "The Definition of the Term Double Star," R. G. Aitken, Ast. Nachr., 188, 281 (1911). 
2 "Ueber die Vertheilung der Sterne auf der nordlichen Halb-kugel . . . ," H. Seeliger, 
Miincken, Sitz. Ber. Ak. Wiss., 1884, Heft 4. 
^ "Second Catalogue of Spectroscopic Binary Stars," W. W. Campbell, Lick Obs. Bull., 
6, 41 (1910). 
