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ANNUAL REPORT SMITHSONIAN INSTITUTION, 1936 

 Table 2.- — Orbits of visual binaries classified by eccentricity 



Table 2 is concerned with observations of 116 stars; for 83 the 

 eccentricity of orbit is less than 0.6, and for 33 stars it is greater than 

 0.6. The last column shows the statistical distribution of eccentrici- 

 ties we should find in a group of stars in which the process of energy- 

 sharing was complete, the group being chosen to be of such a size 

 that there are again 83 stars of eccentricity less than 0.6. A compari- 

 son of this and the preceding column shows that the energy-sharing 

 process is fairly complete up to eccentricity 0.6, but that for eccen- 

 tricities higher than 0.6, there is very little evidence of energy-shar- 

 ing. These stars of high eccentricity correspond to very slow "pen- 

 dulums", but we must not overlook that our table may be incomplete 

 on the observational side, since binary stars of eccentricity greater 

 than about 0.6 are difficult to detect and still more difficult to measure. 



The visual binaries of eccentricity less than about 0.6 form a range 

 of pendulums in which the process of energy-sharing requires a time 

 of millions of millions of years. In another class of binary stars, the 

 spectroscopic binaries, the components lie much closer together — so 

 close in fact that the gravitational forces from other stars have very 

 little effect in modifying their orbits. In these stars, the process of 

 energy-sharing is a matter of hundreds of millions of millions of 

 years at least. Table 3 contains statistics as to the orbits of these 

 stars. We see at once that there is no appreciable sharing of energy. 



Table 3. — Orbits of spectroscopic binaries classified by eccentricity 



