ABSTRACT
Interstellar extinction measurements were extended into the ultraviolet beyond 2200 Å by Stecher [1,2], Bless et al. [3], and Bless and Savage [4,5]. A conspicuous feature in many of the extinction curves occurs at about 2200 Å, apparently varying in shape. This same absorption feature occurs for stars in widely separated galactic regions and has been postulated to be caused by carbon, silica, iron, or combinations (see, e.g., Ref. 6) [29]. Also, interstellar silicate absorption has been observed near 10 µm in the infrared, and this has further emphasized the existence of silicates in the interstellar medium [7].
