MEASURING HEAT FROM STARS 44i 



star systems. There are no doubt many blue and yellow stars having 

 companions which have become so cool and nonluminous that their 

 presence can not be detected photographically. To the eye the star 

 will appear to be blue or yellow. A good illustration is the ordinary 

 paraffin candle. To the eye it looks yellow, because the red-hot wick 

 contributes but little to the total luminous output. But the red-hot 

 wick is very rich in infra-red radiations, as compared with the luminous 

 flame, and when measured with a thermopile (or some other similar 

 radiometer), and an absorption cell, it is found that the red-hot wick 

 contributes materially to the total energy radiated from the flame. 

 In a similar manner a red-hot star will contribute materially to the 

 total radiation from a star system which appears to be blue. The con- 

 spicuous star p Ononis (Eigel) is an excellent illustration. As- 

 tronomers have classified it" B 8 f" the letter " p " meaning that it has 

 a peculiar spectrum. Whether this peculiarity is sufficiently definite to 

 indicate that there is a companion star, the writer does not know. 

 However, the writer's radiometric classification, Table II., would place 

 it with the yellowish-red stars having a transmission of some 40 per 

 cent, through the absorption cell, instead of with the blue stars. No 

 doubt this star has a dark companion which has thus far escaped 

 detection. 



An excellent example which the writer desired to study, but was 

 prevented owing to the fact that at that time (August, 1914) the star 

 does not rise before dawn, is Sirius. This star has a companion which 

 has become so cool that it is rated as a tenth-magnitude star. Although 

 the presence of a companion star was suspected, the light coming from 

 it is so weak that in the presence of the bright star (Sirius), for some 

 years, it defied detection. This companion star is of enormous size, 

 being one half as massive as the bright component; but it sends out only 

 ,1/30,000 as much light. It would have been very interesting to de- 

 termine what amount of radiation from this star system is transmitted 

 through the water cell. 



Two stars having 5th magnitude companions were studied, viz., 

 P Pegasi and a HercuUs. Both stars appeared to have an excessive 

 amount of total radiation in comparison with their photometric bright- 

 ness. In the case of a HercuUs the companion star caused a deflection 

 of almost a centimeter on the galvanometer scale. In Table II. it will 

 be noticed that this star has the lowest transmission through the water 

 cell. Xo doubt this is attributable to the large amount of infra-red 

 radiations contributed by the companion star, which caused galvanom- 

 eter deflections about Ys those obtained from the bright component. 



Attention has already been called to the fact that the receiver, which 

 was attached to the thermojunction, was very small. It was therefore 

 possible to measure the radiations from different parts of the surface of 



