Detection Of CH3+ In The O-rich Planetary Nebula NGC 6302

Planetary nebulae are sites where ejected stellar material evolves into complex molecules, but the precise physical conditions and chemical routes that govern these processes are unclear.

The presence of abundant carbon-rich molecules in O-rich environments poses particular challenges. Here we report the first detection of methyl cation (CH₃+) in any planetary nebula, observed in the O-rich nebula NGC 6302 using JWST MIRI/MRS observations. CH₃+ is a key driver of organic chemistry in UV-irradiated environments.

Spatially resolved observations reveal that CH₃+ is co-located with ¹²CO, H₂, H II, HCO+, and Polycyclic aromatic hydrocarbons (PAHs). LTE modelling of the CH₃+ emission yields excitation temperatures of 500-800K in the inner bubble and torus, rising to 1000-2000K in the outer bubble of NGC 6302, with column densities ranging from ~10^11 to 10^13 cm^-2.

This detection demonstrates that hydrocarbon radical chemistry must be incorporated into planetary nebulae chemical models. Further near-IR observations are crucial to map different chemical networks operating in these environments.

Charmi Bhatt (1 and 2), Jan Cami (1, 2 and 3), Els Peeters (1, 2 and 3), Nicholas Clark (1), Paula Moraga Baez (4), Kevin Volk (5), G. C. Sloan (5 and 6), Joel H. Kastner (4 and 7 and 8), Harriet L. Dinerstein (9), Mikako Matsuura (10), Bruce Balick (11), Kathleen E. Kraemer (12), Kay Justtanont (13), Olivia Jones (14), Raghvendra Sahai (15), Isabel Aleman (16), Michael J. Barlow (17), Jeronimo Bernard-Salas (18 and 19), Joris Blommaert (20), Naomi Hirano (21), Patrick Kavanagh (22), Francisca Kemper (23, 24 and 25), Eric Lagadec (26), J. Martin Laming (27), Frank Molster (28), Hektor Monteiro (29 and 30), Anita M. S. Richards (31), N. C. Sterling (32), Maryam Torki (23), Peter A. M. van Hoof (33), Jeremy R. Walsh (34), L. B. F. M. Waters (35 and 36), Roger Wesson (29 and 17), Finnbar Wilson (29), Nicholas J. Wright (37), Albert A. Zijlstra (31 and 38) ((1) Department of Physics and Astronomy, University of Western Ontario, (2) Institute for Earth and Space Exploration, University of Western Ontario, (3) SETI Institute, (4) Center for Imaging Science, Rochester Institute of Technology, (5) Space Telescope Science Institute, (6) Department of Physics and Astronomy, University of North Carolina, (7) School of Physics and Astronomy, Rochester Institute of Technology, (8) Laboratory for Multiwavelength Astrophysics, Rochester Institute of Technology, (9) Department of Astronomy, University of Texas at Austin, (10) Cardiff Hub for Astrophysics Research and Technology (CHART), School of Physics and Astronomy, Cardiff University, (11) Department of Astronomy, University of Washington, (12) Institute for Scientific Research, Boston College, (13) Chalmers University of Technology, Onsala Space Observatory, (14) UK Astronomy Technology Centre, Royal Observatory, (15) Jet Propulsion Laboratory, California Institute of Technology, (16) Laboratorio Nacional de Astrofisica, (17) Department of Physics and Astronomy, University College London, (18) ACRI-ST, Centre d’Etudes et de Recherche de Grasse (CERGA), (19) INCLASS Common Laboratory, (20) Astronomy and Astrophysics Research Group, Department of Physics and Astrophysics, Vrije Universiteit Brussel, (21) Academia Sinica Institute of Astronomy and Astrophysics, (22) Department of Physics, Maynooth University, (23) Institut de Ciencies de l’Espai (ICE, CSIC), (24) ICREA, (25) Institut d’Estudis Espacials de Catalunya (IEEC), (26) Universite Cote d’Azur, Observatoire de la Cote d’Azur, CNRS, Lagrange, (27) Space Science Division, Naval Research Laboratory, (28) Leidse instrumentmakers School, (29) Cardiff Hub for Astrophysics Research and Technology (CHART), School of Physics and Astronomy, Cardiff University, (30) Instituto de Fisica e Quimica, Universidade Federal de Itajuba, (31) Jodrell Bank Centre for Astrophysics, Department of Physics & Astronomy, The University of Manchester, (32) University of West Georgia, (33) Royal Observatory of Belgium, (34) European Southern Observatory, (35) Department of Astrophysics/IMAPP, Radboud University, (36) SRON Netherlands Institute for Space Research, (37) Astrophysics Research Centre, Keele University, (38) School of Mathematical and Physical Sciences, Macquarie University)

Subjects: Astrophysics of Galaxies (astro-ph.GA)
Cite as: arXiv:2509.14556 [astro-ph.GA] (or arXiv:2509.14556v1 [astro-ph.GA] for this version)
https://doi.org/10.48550/arXiv.2509.14556
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Submission history
From: Charmi Bhatt
[v1] Thu, 18 Sep 2025 02:37:52 UTC (3,231 KB)
https://arxiv.org/abs/2509.14556
Astrobiology, Astrochemistry,