Our aim is to determine the isotopic ratios {12C/13C}{} and {14N/15N}{} in a variety of comets and link these measurements to the formation and evolution of the solar system. The {12C/13C}{} and {14N/15N}{} isotopic ratios are measured {for} the CN radical by means of high-resolution optical spectra of the R branch of the B-X (0,0) violet band. {23 comets from different dynamical classes} have been observed, sometimes at various heliocentric {and nucleocentric} distances, in order to estimate possible variations of the isotopic ratios in parent molecules. The {12C/13C}{} and {14N/15N}{} isotopic ratios in CN are remarkably constant (average values of, respectively, 91.0±3.6 and 147.8±5.7) within our measurement errors, for all comets whatever their origin or heliocentric distance. While the carbon isotopic ratio does agree with the terrestrial value (89), the nitrogen ratio is a factor of two lower than the terrestrial value (272), indicating a fractionation in the early solar system, or in the protosolar nebula, common to all the comets of our sample. This points towards a common origin of the comets independently of their birthplaces, and a relationship between HCN and CN.
@article{arxiv.0907.0311,
title = {The CN isotopic ratios in comets},
author = {J. Manfroid and E. Jehin and D. Hutsemékers and A. Cochran and J. -M. Zucconi and C. Arpigny and R. Schulz and J. A. Stüwe and I. Ilyin},
journal= {arXiv preprint arXiv:0907.0311},
year = {2015}
}