On the opacity of the interstellar medium to ultrasoft X-rays and extreme-ultraviolet radiation.

Abstract

The opacity of the interstellar medium at soft X-ray and extreme-ultraviolet wavelengths has been reexamined in the light of recent evidence that the density of interstellar hydrogen in the solar neighborhood may be quite low. It is shown that the distance at which significant attenuation occurs is not negligible, especially in the 50-300 Â region. Subject headings: interstellar matter-opacities-ultraviolet-X-rays In dim eclipse disastrous twilight sheds On half the nations, and with fear of change Perplexes monarchs.