20 



KNOWLEDGE. 



January, 1911. 



spectroscopic history, both of constitution and of " It is true that of these « Crucis is not a Binary, 



radial speed, including for each the proper motion It is perhajis all the more remarkable for that reason, 



and its solar comjwnent. we shall be in a position to being one of the brightest stars in the skv, and shown 



attack questions relating to the constitution of the by photography to be surrounded by a cluster, or rather 



1 2703 Dulphini. 

 Mags. 7i, 7t, 7i : Distances 25", 71", 5'/'. 



> Dilphiiii. 

 MaKs. 4i, 5.; : Distance 11" 



ji Cephei. 

 Mags. 3t, S: Distance 13", 



Cephei. 



Mags. 5i. 8A, si, 10: Distances li", 12", 20" 



sidereal heavens, which are to-da\' be\-ond the realms 

 of reasonable speculation. In this respect the stars 

 of the Soutliern hemisphere offer at least as attractive 

 a held of investigation as those N<irth of the equator. 

 In spite of neglect, the Southern s\-stems alread\- 

 exceed in importance those of the North, .\mong 

 them may be quoted : — 



bv rings, of ver\- faint stars, in the centre of wliich 



Sirius 

 (X Centauri 

 y V'irginis 

 y Liipi 

 y Centauri 

 y Circini 

 y Sextantis 

 ^ Aquarii 



4 



T 



Eridani 



Crucis 



Muscae 



Aquarii 



Scorjiii 



Liipi 



Phoenicis 



Sagittarii 



the two large stars are. as far as can be ascertained, 

 absolutely stationar\-. Are these gloriously brilliant 

 stars devoid of mass, or, it the\- shine with an 

 intrinsic brillianc\- of surface e(|ual to that of Sirius. 



at what distance must the}- l>e apari. Limi. g, 



t that gravitational 

 motion becomes too small tn be detected even 

 in a centur\- ? Speculation and analogy alike fail 

 us. and a systematic study of all Double Stars is alone 

 likeK- to solve these and many other allied questions. 

 The high eccentricity of the orbits of some Double 

 Stars, including a Centauri, subjects the internal 

 constitution of the components to tlifferent pressures 

 at the times tif pcii-astron and ap-astron. Does 

 this affect their spectia in a measurable degree?"* 



'■' Reference Cataii 



igni- of Sonthern Doable Stars, page xiii a. 



