MIRACLES OF SCIENCE 



jointly more than three times (3.7) the mass of the 

 sun. The double star known as 85 Pegasi has a mass 

 more than eleven times that of the sun; and the 

 average mass of the first six pairs of the double stars 

 to be weighed is 3.5 times that of the sun. Mean- 

 time the average radiating power is nearly six times 

 that of the sun. So far as these limited observations 

 go, they give warrant to the belief that the sun is a 

 relatively dull star. 



In some cases it is possible, with the aid of the 

 modern instruments, to determine the orbits of a 

 pair of double stars so accurately that the relative 

 displacement and therefore the relative sizes of the 

 two may be computed. In the case of Sirius, for 

 example, it appears that the larger member of the 

 pair is 2.5 and the smaller member 1.2 times the size 

 of the sun. It is notable that, although the two 

 bodies are thus not so very different in size, the 

 larger one is nearly 10,000 times as bright as its 

 companion. So great a discrepancy in the brilliancy, 

 in the case of bodies of comparable size, is not easily 

 accounted for. But an even greater difficulty arises 

 when we attempt to explain the case of 85 Pegasi, 

 in which it is computed that one member of the pair 

 is 4.3 times and the other Y.8 times the size of the 

 sun, and in which the smaller member is 100 times 

 as luminous as the larger. Professor Moulton points 

 out that, according to the usual estimates made from 

 spectroscopic appearances, this pair of stars should 

 be much older than the Sirius couple, and that anal- 

 ogy would lead us to expect the smaller mass to be 

 approaching the dark stage, instead of being exceed- 



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