The moon and the planets

, Volume 18, Issue 4, pp 441–446 | Cite as

The12C/13C isotope ratio in comets, stars and interstellar matter

  • Vladimír Vanýsek
  • Jürgen Rahe
Article
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Abstract

The12C/13C isotope ratio in the interstellar medium and in stellar atmospheres is discussed and compared to the value found in the solar system and especially in comets. The cometary value (≥100) tends to be slightly above the terrestrial value and is definitively higher than that for interstellar molecular clouds (about 30 to 50).

This result implies that comets are not of interstellar origin; that the “original” isotopic abundances of the primitive solar nebula has been preserved in the cometary material; and that due to an enrichment of the interstellar medium in13C, the12C/13C isotope ratio has decreased by a factor of about 2.5 since the formation of the solar system (i.e., during the past 4.5×109 years) — a result which is roughly in agreement with present theories of the chemical evolution of our Galaxy. The relatively high cometary carbon isotope ratio (as compared to the terrestrial value) indicates that some correction should be applied to the semi-empirical models describing the13C enrichment in the Galaxy.

Keywords

Atmosphere Isotope Ratio Solar System Carbon Isotope Interstellar Medium 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
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Copyright information

© D. Reidel Publishing Company 1978

Authors and Affiliations

  • Vladimír Vanýsek
    • 1
  • Jürgen Rahe
    • 2
  1. 1.Department of Astronomy and AstrophysicsCharles UniversityPragueCzechoslovakia
  2. 2.Remeis-Sternwarte BambergAstronomisches Institut der Universität Erlangen-NürnbergBayernGermany

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