﻿NO. 5 SMITHSONIAN EXPLORATIONS, I922 27 



ASTROPHVSICAL FIELD-WORK IN CALIFORNIA, ARIZONA, 



AND CHILE 



The Astrophysical Observatory of the Institution did some notable 

 work at Mount Wilson on the spectra of the sun and stars. Some 

 discrepancy had appeared between the work of 1920 and the early 

 work of the observatory prior to 1910 on the distribution of energy 

 in the sun's spectrum as it is outside the atmosphere. It appeared 

 necessary to go over this ground again, as the result is used in every- 

 day work at the two field stations in Chile and Arizona, in computing 

 the solar constant of radiation, so the work was repeated by Messrs. 

 Abbot and Aldrich with as much variety in conditions as was possible. 

 The results of the different experiments were in close accord, and 

 in accord with the work of 1920. so that the new determination is 

 now going into effect in the computations in Arizona and Chile. 



At the invitation of Director Hale, of the Mount Wilson Observa- 

 tory, Messrs. Abbot and Aldrich employed the great hundred-inch 

 telescope there in connection with a special vacuum bolometer and 

 galvanometer designed and constructed at Washington in order to 

 measure the heat in the spectrum of the brighter stars. In other words, 

 they attempted to investigate the distribution of radiation in the stellar 

 spectra with the bolometer as they have long done with regard to the 

 spectrum of the sun. When one thinks of taking the light of a star, 

 which looks like a firefly up in the sky, separating it out into a long 

 spectrum, and observing the heat in the different parts of the spec- 

 trum, it seems a practical impossibility. Nevertheless, the observers 

 succeeded in doing this for ten of the brighter stars, and they also 

 observed the sun's spectrum with the same apparatus. In this way 

 it was possiljle to represent the distribution of radiant energy in the 

 different types of stars from the bluest to the reddest ones, and to 

 know the displacement of the maximum of energy from shorter to 

 longer wave-lengths as the color of the stars tended more and more 

 towards the red. 



The outlook for further investigations of this kind is hopeful, and 

 it will have a notable value in the estimation of the temperatures of 

 the stars and the study of stellar evolution. 



The two field stations at Mount Harqua Hala, Arizona, and Mount 

 Montezuma, Chile, are continued in operation. The station on Mount 

 Harqua Hala. under the direction of Mr. Moore, has been much im- 

 proved during the year. Owing to the driving rains and high winds, 

 it proved necessary to sheathe the adobe building there with galva- 



