A rich hydrocarbon chemistry and high C to O ratio in the inner disk around a very low-mass star

Author(s)

B. Tabone, G. Bettoni, E.~F. van Dishoeck, A.~M. Arabhavi, S. Grant, D. Gasman, Th. Henning, I. Kamp, M. Güdel, P.~O. Lagage, T. Ray, B. Vandenbussche, A. Abergel, O. Absil, I. Argyriou, D. Barrado, A. Boccaletti, J. Bouwman, A. Caratti o Garatti, V. Geers, A.~M. Glauser, K. Justannont, F. Lahuis, M. Mueller, C. Nehmé, G. Olofsson, E. Pantin, S. Scheithauer, C. Waelkens, L.~B.~F.~M. Waters, J.~H. Black, V. Christiaens, R. Guadarrama, M. Morales-Calderón, H. Jang, J. Kanwar, N. Pawellek, G. Perotti, A. Perrin, D. Rodgers-Lee, M. Samland, J. Schreiber, K. Schwarz, L. Colina, G. Östlin, G. Wright

Abstract

Carbon is an essential element for life but how much can be delivered to young planets is still an open question. The chemical characterization of planet-forming disks is a crucial step in our understanding of the diversity and habitability of exoplanets. Very low-mass stars (less than 0.2 M

_⊙) are interesting targets because they host a rich population of terrestrial planets. Here we present the James Webb Space Telescope detection of abundant hydrocarbons in the disk of a very low-mass star obtained as part of the Mid-InfraRed Instrument mid-INfrared Disk Survey (MINDS). In addition to very strong and broad emission from C

₂H

₂ and its

¹³C

¹²CH

₂ isotopologue, C

₄H

₂, benzene and possibly CH

₄ are identified, but water, polycyclic aromatic hydrocarbons and silicate features are weak or absent. The lack of small silicate grains indicates that we can look deep down into this disk. These detections testify to an active warm hydrocarbon chemistry with a high C/O ratio larger than unity in the inner 0.1 astronomical units (AU) of this disk, perhaps due to destruction of carbonaceous grains. The exceptionally high C

₂H

₂/CO

₂ and C

₂H

₂/H

₂O column density ratios indicate that oxygen is locked up in icy pebbles and planetesimals outside the water iceline. This, in turn, will have important consequences for the composition of forming exoplanets.

Organisation(s)

Department of Astrophysics

External organisation(s)

Université Paris Saclay, Leiden University, University of Groningen, Max-Planck-Institut für extraterrestrische Physik, Katholieke Universiteit Leuven, Max-Planck-Institut für Astronomie, Dublin Institute for Advanced Studies, Université de Liège, Centre for Astrobiology (CAB), CSIC-INTA, Paris Observatory, The Royal Observatory, Edinburgh, Eidgenössische Technische Hochschule Zürich, Chalmers University of Technology, SRON Netherlands Institute for Space Research , Stockholm University, Radboud University, Hungarian Academy of Sciences, Sorbonne Université, INAF Astronomical Observatory of Capodimonte , Österreichische Akademie der Wissenschaften (ÖAW)

Journal

Nature Astronomy

Volume

7

Pages

805-814

No. of pages

10

ISSN

2397-3366

DOI

https://doi.org/10.1038/s41550-023-01965-3

Publication date

07-2023

Peer reviewed

Yes

Austrian Fields of Science 2012

103004 Astrophysics

Keywords

ASJC Scopus subject areas

Astronomy and Astrophysics

Portal url

https://ucrisportal.univie.ac.at/en/publications/7eb74587-9452-4c1c-a3d3-fb8cc3ea73ee