Distribution Of Interstellar Hydrogen Research Articles

Variability of the neutral hydrogen density distribution due to solar cycle related effects

The influence of the realistic solar cycle variability of the solar Lyman-α radiation pressure and ionisation rate on the distribution of interstellar hydrogen within heliosphere is analysed. The temporal evolution of density is discussed and compared with the results of the static, classical “hot” model computed for various sets of ionisation rate and radiation pressure values. It is shown that the density variations are especially pronounced along the downwind direction and result in density waves smearing out only beyond about 60 AU, while in the upwind region non-negligible modulations extend to about 20 AU. Discussion of the influence of the hydrogen density variation on the interplanetary Lyman-α backscattered glow observed from 1 AU is provided along with some comments on the applicability of the static, classical “hot” model as an interpretation tool for these observations.

Helen B. Warner Prize

The American Astronomical Society has announced the award of its Helen B. Warner Prize to Maarten Schmidt, professor of astronomy at the California Institute of Technology and staff member of the Mt. Wilson and Palomar Observatories. The prize, which honors a significant contribution to astronomy by a scientist under thirty‐five, was given to Dr. Schmidt for his spectroscopic studies of radio galaxies and quasistellar radio sources. One of his contributions was the photographic identification of the quasistellar radio source 3C273. He suggested that its spectral lines could be attributed to hydrogen if one assumed a red shift of 16 percent. Such a large red shift had previously been observed only in the most distant galaxies. His main interests have been the distribution of mass in the Galaxy, spiral structure and distribution of interstellar hydrogen in the Galaxy, statistics of star formation and its effects on the evolution of galaxies, and spectra of extragalactic radio sources.