Astronomy and Astrophysics – Astronomy
Scientific paper
Jan 2005
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005hia....13..495w&link_type=abstract
Highlights of Astronomy, Vol. 13, as presented at the XXVth General Assembly of the IAU - 2003 [Sydney, Australia, 13 - 26 July
Astronomy and Astrophysics
Astronomy
1
Scientific paper
Evidence for interstellar material in comets is deduced from IR spectra insitu measurements of Halley and chondritic porous interplanetary dust particles (CP IDPs). IR spectra of comets reveal the spectrally active minerals: amorphous carbon amorphous silicates and (in some comets) crystalline silicates. Evidence suggests amorphous silicates are of interstellar origin while crystalline silicates are of nebular origin.
10µm spectra of comets and submicron amorphous silicate spherules in CP IDPs have shapes similar to lines-of-sight through the ISM. Thermal emission models of cometary IR spectra require Fe-bearing amorphous silicates. Fe-bearing amorphous silicates may be Fe-bearing crystalline silicates formed in AGB outflows that are amorphized through He+ ion bombardment in supernova shocks in the ISM.
Crystalline silicates in comets as revealed by IR spectra and their apparent absence in the ISM argues for their nebular origin. The high temperatures (>1000 K) at which crystals form or are annealed occur in the inner nebula or in nebular shocks in the 5 [Truncated.]
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