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Highlights - Volume 503-2 (August IV 2009)

Details: Published on 18 August 2009

HIGHLIGHTS: this week in A&A

Volume 503-2 (August IV 2009)

In section 10. Planets and planetary systems

“The CN isotopic ratios in comets”, by J. Manfroid, E. Jehin, D. Hutsemékers, A. Cochran, J.-M. Zucconi, C. Arpigny, R. Schultz, J.A. Stuwe, and I. Ilyin, A&A 503, p. 613

The study of isotopic compositions is of considerable importance for understanding the formation of the solar system. Manfroid et al. present high-resolution spectroscopic observations of 23 comets with several telescopes (VLT, NOT, Harlan F Smith, Keck) in the violet band of CN, aimed at measuring their isotopic composition in C and N. The data demonstrate an astonishing homogeneity of these isotopic signatures. The 12C/13C ratio is very similar to that of other solar system bodies including terrestrial planets. In contrast, comets are strongly enriched in 15N vs. 14N compared to the Earth or the Sun. This raises the question of the origin of the heterogeneity in the N isotopic composition in the solar system.

In section 2. Astrophysical processes

“The photodissociation and chemistry of CO isotopologues: applications to interstellar clouds and circumstellar disks”, by R. Visser, E.F. van Dishoeck, and J.H. Black, A&A 503, p. 323

Visser et al. study the isotope-selective photodissociation of the CO molecule and its effects on the chemistry of CO and on its isotopologues, in interstellar clouds and circumstellar disks. They find that the photodissociation rate in the unattenuated interstellar radiation field is about 30% higher than currently-adopted values, and their work supports the hypothesis that CO photodissociation is responsible for the anomalous 17^O and 18^O abundances in meteorites.

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