Direct evidence of multiple reservoirs of volatile nitrogen in a protosolar nebula analogue

¹ Institut Universitaire de France, 75231 Paris Cedex 05, France
² Université Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
e-mail: pierre.hily-blant@univ-grenoble-alpes.fr
³ Chester F. Carlson Center for Imaging Science, School of Physics & Astronomy, and Laboratory for Multiwavelength Astrophysics, Rochester Institute of Technology, 54 Lomb Memorial Drive, Rochester, NY 14623, USA
⁴ Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA

Received: 30 January 2017
Accepted: 23 June 2017

Abstract

Isotopic ratios are keys to understanding the origin and early evolution of the solar system in the context of Galactic nucleosynthesis. The large range of measured ¹⁴N/¹⁵N isotopic ratios in the solar system reflects distinct reservoirs of nitrogen whose origins remain to be determined. We have directly measured a C¹⁴N/C¹⁵N abundance ratio of 323 ± 30 in the disk orbiting the nearby young star TW Hya. This value, which is in good agreement with nitrogen isotopic ratios measured for prestellar cores, likely reflects the primary present-day reservoir of nitrogen in the solar neighbourhood. These results support models invoking novae as primary ¹⁵N sources as well as outward migration of the Sun over its lifetime, and suggest that comets sampled a secondary, ¹⁵N-rich reservoir during solar system formation.