176 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1964 



many of the observations at Harvard's Agassiz Station. The con- 

 tinuous flux and HS, Hy, and H^ profiles for Vega were predicted 

 remarkably well by a model atmosphere that included opacities caused 

 by the blended wings of the higher Balmer and Lyman lines. The 

 effective temperature of the model that best reproduced the observa- 

 tions matched that derived from recent measurements of this star's 

 radius. 



Dr. Gingerich has investigated the role of opacities from metals in 

 stellar atmospheres,^^ finding good agreement between a predicted 

 model and the solar rocket ultraviolet observations, and also showing 

 that such opacities must be considered even in much hotter stars, such 

 as Sirius, which probably has anomalously high metal abundances. 

 In the work with S. S. Kumar on cool stars, with effective tempera- 

 tures from 2,500 to 4,500°, he found unusually sharp maxima in the 

 infrared spectrmn near 16,500 A, which have been partially confirmed 

 by the Princeton Stratoscope balloon observations. Electron and 

 Eayleigh scattering has been incorporated into a stellar atmosphere 

 computer program, both for the cool stars and for hotter stars. With 

 this program David Latham has been able to show that the introduc- 

 tion of convection into a consistent nongray solar model has little 

 effect on the overlying temperature structure, and no effect on the 

 visible spectrum. 



Dr. "Wolfgang Kalkofen is developing a model whose aim is to 

 predict the radiation from variable stars.^^ This involves the cal- 

 culation of the radiation field emerging from a medium that departs 

 from local thermodynamic equilibrium, and that is in motion, with 

 a velocity dependent upon position in the medium. 



Drs. Colombo and Whitney are studying a nonlinear autonomous 

 system with two or three degrees of freedom. This system is chosen 

 to simulate the mechanics of a pulsating star. 



Dr. Mitler has made theoretical study of the isotope abundances of 

 the light elements. He shows that the obsei-ved abimdances of Li, 

 Be, and B can be explained by their spallation in small, prototerres- 

 trial bodies. He considers spheres of arbitrary composition and 

 radius irradiated by protons and finds that the present-day proton 

 flux is too soft to give the desired results reasonably, and that a mean 

 proton energy of 300 mev is necessary to get the obsei"\'ed isotopic 

 ratios. The results are not sensitive to the composition, and he can 

 obtain the measured Li, Be, and B abundances by taking dry silicate 

 spheres of about 14 m radius for the prototerrestrial bodies, 140 m 

 for the protoasteroidal bodies. 



See footnotes, p. 177. 



