278 ASTRONOMY: H. SHAPLEY 
The Distribution of 5000 Stars in co Centauri 
SECTORS 
WIDTH or RING 
MEAN 
15" 
75° 
105° 
135° 
165° 
195° 
225° 
255° 
285° 
315° 
345° 
3' to 6' 
148 
129 
151 
182 
165 
159 
164 
173 
203 
182 
198 
163 
168 
84 
89 
151 
142 
139 
113 
105 
119 
153 
163 
125 
117 
125 
9 to 12 
66 
81 
96 
74 
64 
79 
64 
68 
88 
97 
74 
68 
77 
12 to 15 
44 
54 
61 
61 
57 
57 
40 
59 
57 
59 
51 
45 
54 
3 to 9 
232 
218 
302 
324 
304 
272 
269 
292 
356 
345 
323 
280 
293 
9 to 15 
110 
135 
157 
135 
121 
136 
104 
127 
145 
156 
125 
113 
130 
3 to 15 
342 
353 
459 
459 
425 
408 
373 
419 
501 
501 
448 
393 
423 
8 
6 
17 
12 
9 
5 
2 
16 
11 
17 
16 
9 
11 
the elliptical distribution is present at all distances from the center. 
The irregularities and other evidence of the lack of exact symmetry in 
this cluster, as well as in others, probably represent actual conditions; 
their significance may be much the same as that of the open star groups 
and the breaks in the Milky Way in the symmetry of our own galactic 
system. 
90° 120° 150° 0° 30° 60° 90° 120° 150° 
+ 60^ 
+ 30 
0 
-30 
-60 
The full line shows the distribution of all stars, the minimum corresponding to the direc- 
tion of the cluster's galactic pole. The dotted line shows the distribution of variables. Or- 
dinates, percentage deviation of the number of stars in each sector from the mean for all 
sectors; abscissae, angle of direction from the center, expressed as position angle. 
There are 128 variables (nearly all short-period Cepheids) in co^ Cen- 
tauri. Their distribution is given in the last line of the table, and their 
relation to the axis of symmetry is shown in figure 2. In the diagram, 
numbers for opposite sectors are combined and the percentage devia- 
tions from the means are plotted together with a similar curve for the 
five thousand stars of all kinds outside the central area. The preference 
for the sectors that lie along the axis of symmetry is very conspicuous, 
the relative ampHtudes of the two curves showing that these short- 
period variables are three times as condensed toward the supposed plane 
of symmetry as the stars in general. A correction for superposed^ stars 
increases the general ellipticity by about one-tenth of its amount. 
