Further measurements of amorphous silicates

Abstract

Extinction measurements were made for two synthetic magnesium silicates in the range from 7 to 300 microns. The measurements were made over the temperature range from 77 to 393 K. The amorphous materials have peak absorptions in the 10-micron region that are a factor of 2 to 3 smaller than those of more highly structured silicates. The optical properties of these materials are compared with those derived for the grains in front of VI Cygni No. 12, and it appears that one type of material could simultaneously account for both infrared and optical extinction. Temperatures which might be encountered in space could alter the ratio of 10-micron to 20-micron absorption by about a factor of 2. The far-infrared properties of these materials suggest they could supply a significant amount of the far-infrared emission noted in astronomical sources such as the Orion Nebula.