The Interstellar Carbon Budget and the Role of Carbon in Dust
and Large Molecules
Theodore P. Snow (1)
and
Adolf N. Witt
Published data on stellar composition show that carbon in the sun
is substantially more abundant than in other stars. A carbon abundance
of 225 carbon atoms per 10
hydrogen atoms is
representative of galactic stars, whereas published values for the sun
range from 350 to 470 carbon atoms per 10
hydrogen atoms.
Other elements are also present in enhanced quantities in the solar
system, consistent with suggestions that a supernova event was closely
associated with the formation of the solar system. The overabundance of
carbon in the solar system has many important implications, including
new constraints on nucleosynthesis models for supernovae and
substantial modification of the so-called ``cosmic''
composition
normally adopted in discussions of galactic and interstellar
abundances. A reduction in the galactic carbon budget, as suggested by
the stellar composition data, strongly constrains the quantity of
carbon that is available for the formation of interstellar dust, and
some dust models now appear implausible because they require more
carbon than is available.
T. P. Snow is at the Center for Astrophysics and Space Astronomy,
University of Colorado, Boulder, CO 80309, USA. A. N. Witt is at the
Ritter Observatory, University of Toledo, Toledo, OH 43606, USA.
(1) To whom correspondence should be addressed.