Mathematics – Logic
Scientific paper
Aug 1991
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1991anpcs..16..507r&link_type=abstract
Ann. Phys. (Paris) Colloq., Vol. 16, No. 4, p. 507 - 513
Mathematics
Logic
Carbon: Circumstellar Shells, Carbon: Planetary Nebulae, Carbon Stars: Interstellar Matter
Scientific paper
A recent count of the stars leaving the main sequence and the method to estimate the return of matter to the interstellar medium due to mass-loss is summarized. Stars of (1 - 5)Msun would replenishc the interstellar medium in (6 - 12)×109 years. Carbonaceous compounds of the interstellar dust are believed to be formed in the atmosphere of carbon stars, but the author brings evidences that the fraction of it made of very small particles and most frequently referred to as polycyclic aromatic hydrocarbons (PAH), which on average are believed to accommodate >15% of the interstellar carbon, are nor formed as soon as the dust condenses in the atmosphere of red giants. Some kind of processing seems to be required, very likely induced by the exposition of the dust to the ultraviolet radiation of the central star when the red giant becomes a planetary nebula. Heating of small grains by hard photons is believed to heat them to high enough a temperature to produce some morphological or crystallographic evolution, roughly from aliphatic to aromatic structure.
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