ASTRONOMY: W. S. ADAMS 
417 
THE RADIAL VELOCITIES OF THE MORE DISTANT STARS 
By Walter S. Adams 
MOUNT WILSON SOLAR OBSERVATORY. CARNEGIE INSTITUTION OF WASHINGTON 
Presented to the Academy, June 8. 1915 
As a result of the work of Kapteyn, Campbell, and Boss it has been 
recognized for some years that the linear motions of the brighter stars 
vary with their spectral types, the velocities of the solar type stars 
being higher than those of t3qDes B and A. It is equally well-known, 
however, that the solar type stars in general have larger proper motions 
and so are much nearer to the sun than those of earlier types. Hence 
the stars, for which the velocities have been compared, have quite differ- 
ent distances, and if, as was once suggested by Eddington,^ the nearer 
stars move more rapidly than the distant ones this fact would account, 
in part at least, for the apparent variation of velocity with spectral type. 
In the course of an analysis of the radial velocity results from the 
Lick Observatory and Mount Wilson, J. C. Kapteyn derived the rela- 
tionship between radial velocity and proper motion for the K type 
stars,2 and found that the velocity increased rapidly with the amount of 
proper motion. In this computation the effect of stream motion was 
eliminated to a large extent by a selection of stars nearly 90° from the 
vertices of the streams. The Mount Wilson observations of the spectra 
of stars having both small and large proper motions provide the material 
for a similar comparison for other types of spectra. This is given in 
Table I: the effect of stream motion, however, has not been eliminated. 
The average velocity is corrected for a solar motion of 20 km. directed 
toward the apex 
a =17 h 59 m. 5 = + 30°.8 
and no velocities exceeding 100 km. are included. 
TABLE I 
SPECTRAL 
NUMBER 
v' 
NUMBER 
TYPE 
OF STARS 
OF STARS 
E 
61 
0'.016 
8.2 
52 
0'.041 
9.6 
A 
55 
0 .019 
10.0 
104 
0 .067 
10.7 
F 
20 
0 .011 
10.1 
45 
0 .530 
24.6 
G 
63 
0 .013 
10.6 
69 
0 .670 
24.9 
M 
27 
0 .015 
12.6 
12 
0 .170 
17.6 
To these we may add Kapte>Ti's value for the K stars with stream motion eliminated 
K 
27 
0.013 
10.9 
19 
>0.30 
26.7 
