Identification of Type I Supernova Bands

Abstract

THE variation of polarization with wavelength across the 4430 Å band strongly suggests that the diffuse interstellar absorption bands are due to some component of the interstellar dust (ref. 1 and G. A. H. Walker, private communication). Seddon² has noted coincidences between wavelengths of minima in the spectra of type I supernovae and certain of the diffuse interstellar bands. Although quite a large proportion of interstellar dust may arise from condensation of material ejected from supernovae³, it is likely that dust in clouds and in the interstellar medium is substantially different from that seen in absorption in supernova explosions. Irradiation with cosmic rays and with γ and X-rays is expected to produce defects⁴ and accretion of material by grains is likely to affect their chemical structure. The properties of interstellar grains subjected to these processes are difficult to simulate in the laboratory, particularly when the initial composition of the grains is still uncertain. Thus an identification of the broad supernova bands which originate in dust before its dispersion in the interstellar medium could lead to an understanding of the nature of the interstellar dust component which produces the usual diffuse interstellar bands.