ENERGY SPECTRA OF SOME OF THE 

 BRIGHTER STARS 



By C. G. abbot and L. B. ALDRICH 



Smithsonian Institution 



(With One Plate) 



On several occasions one or both of us have attempted to observe 

 the distribution of heat in the spectra of stars, with a view to the 

 estimation of their approximate temperatures and related conditions.^ 

 On two other occasions Abbot and Stebbins, and Abbot and Hoover, 

 made certain observations of the sort, but these were unfortunately 

 vitiated by effects of stray light. In all these experiments we had the 

 privilege of observing at the Coude focus of the lOO-inch telescope on 

 Mount Wilson, Calif. We acknowledge with grateful thanks the 

 encouragement and assistance given us by the staff of Mount Wilson 

 Observatory. 



On September 7, 8, and 9, 1947, we made measurements with the 

 radiometer on eight stars. The present publication is a preliminary re- 

 port, showing that the way seems open to obtain good results in this 

 manner. We hope to amphfy the results and greatly improve their 

 accuracy in a future expedition which we propose to undertake in 

 September 1948. 



In Smithsonian Publication No. 3843 (Smithsonian Misc. Coll., 

 vol. 104, No. 22) one of us described the apparatus proposed to be 

 used in 1946. The expedition was delayed until 1947 because it was 

 impossible to obtain the compound prism described in Publication 

 3843. A substitute for it was obtained in January 1947. Various 

 delays in setting up the apparatus at Mount Wilson in 1947 prevented 

 us from experimenting long enough to get maximum sensitiveness 

 with the radiometer. Hence not more than a centimeter deflection 

 was obtained for any of the stars observed, and consequently the 

 minute vibrations and Brownian movements of the radiometer caused 

 rather large percentage accidental errors in the observations, as will 

 appear below. Nevertheless the results obtained were positive, and 



1 Smithsonian Misc. Coll., vol. 74, No. 7, 1923; Contr. Mount Wilson Observ., 

 No. 280, 1924; Contr. Mount Wilson Observ., No. 380, 1929. 



SMITHSONIAN MISCELLANEOUS COLLECTIONS, VOL. 107, NO. 19 



