18 



PK0FESS0E A. FOWLEE, F.R.S., OX 



series, which includes the " YVolf-Rayet *' stars, showing spectra 

 chiefly distinguished by bright lines. 



This sequence of various types has been arrived at entirely 



Classification of Stellar Spectra. 



Harvard. 



Seeehi. 



Other titles. 



Special features. 



Examples. 



0 





Wolf-Eayet 



Bright lines of H, He, and 

 unknown. 



y Argus. 



B 





Orion 



Dark lines of H and He 

 predominant ; lines of 

 Si. C. 0. X : enhanced 

 lines of Mg and Ca. 



3, y, o\ e Orio- 

 nis and Vir- 

 ginis. 



A 



i 



Sirian 



Lines of H predominant ; 

 enhanced and arc lines 

 of metals. 



Sirius, Castor, 

 Vega. 



F 



I-II 



Procyonian 



Lines of H less prominent 

 than in A ; metallic 

 lines stronger. 



Procyon, 

 Canopus. 



G 



II 



Solar 



Arc lines of metals, with 

 some enhanced lines. 



Sun, Capella. 



K 



II 



Areturian 



Enhanced lines weaker, 

 and flame lines stronger 

 than in G. 



Arcturus, 

 Pollux. 



M 



III 



Antarian 



Flutings of titanium 

 oxide : flame lines of 

 metals. 



An tares. Mira, 

 Betelgeuse, 

 and Herculis. 



• N 



IV 



Piscian 



Flutings of carbon ; flame 

 lines of metals. 



19 Piscium, 

 152 Schjel- 

 lerup. 



from considerations of the spectral phenomena. It is strongly 

 supported, however, by spectro-photometric observations which 

 lead to approximate estimates of the surface temperatures of 

 the stars. Thus, the Potsdam astronomers have estimated 

 that the temperature of the X or 4th type stars is about 

 3300 degrees C, of the M or 3rd type 4200 degrees C, and so 

 on to 10°300 degrees C. for the A or 1st type stars and 11,600 

 decrees C. for the B stars. These figures may be considerably 



