Williams, G. V. et al. Comet C/2017 u1 (PanSTARRS). Minor Planet Electronic Circulars 2017-U181 (2017).
Denneau, L. et al. 3I/ATLAS = C/2025 n1 (ATLAS). Minor Planet Electronic Circulars 2025-N12 (2025).
Jewitt, D., Hui, M.-T., Mutchler, M., Kim, Y. & Agarwal, J. Hubble Space Telescope observations of the interstellar interloper 3I/ATLAS. Astrophys. J. 990, L2 (2025).
Alarcon, M. R. et al. Deep g′-band imaging of interstellar comet 3I/ATLAS from the Two-meter Twin Telescope (TTT). The Astronomer’s Telegram 17264, 1 (2025).
Seligman, D. Z. et al. Discovery and preliminary characterization of a third interstellar object: 3I/ATLAS. Astrophys. J. 989, L36 (2025).
Cordiner, M. A. et al. JWST detection of a carbon-dioxide-dominated gas coma surrounding interstellar object 3I/ATLAS. Astrophys. J. 991, L43 (2025).
Cordiner, M. et al. Isotopic evidence for a cold and distant origin of the interstellar object 3I/ATLAS. Nature https://doi.org/10.1038/s41586-026-10771-6 (2026).
Harrington Pinto, O., Womack, M., Fernandez, Y. & Bauer, J. A Survey of CO, CO2, and H2O in comets and centaurs. Planet. Sci. J. 3, 247 (2022).
Rahatgaonkar, R. et al. Very Large Telescope observations of interstellar comet 3I/ATLAS. II. From quiescence to glow: dramatic rise of Ni I emission and incipient CN outgassing at large heliocentric distances. Astrophys. J. 995, L34 (2025).
Hutsemékers, D. et al. Pre-perihelion evolution of the NiI/FeI abundance ratio in the coma of the interstellar comet 3I/ATLAS: from extreme to normal. Astron. Astrophys. 706, A43 (2026).
Roth, N. X. et al. CH3OH and HCN in interstellar comet 3I/ATLAS mapped with the ALMA Atacama Compact Array: distinct outgassing behaviors and a remarkably high CH3OH/HCN production rate ratio. Astrophys. J. 999, L32 (2026).
Nomura, H. et al. in Protostars and Planets VII (eds Inutsuka, S. et al.) Vol. 534, 1075 (Astronomical Society of the Pacific, 2023).
Wirström, E. S., Charnley, S. B., Cordiner, M. A. & Milam, S. N. Isotopic anomalies in primitive Solar System matter: spin-state-dependent fractionation of nitrogen and deuterium in interstellar clouds. Astrophys. J. 757, L11 (2012).
Wirström, E. S. & Charnley, S. B. Revised models of interstellar nitrogen isotopic fractionation. Mon. Not. R. Astron. Soc. 474, 3720–3726 (2018).
Hily-Blant, P., Magalhaes de Souza, V., Kastner, J. & Forveille, T. Multiple nitrogen reservoirs in a protoplanetary disk at the epoch of comet and giant planet formation. Astron. Astrophys. 632, L12 (2019).
Rampinelli, L. et al. Radial variations in the nitrogen, carbon, and hydrogen fractionation in the PDS 70 planet-hosting disk. Astron. Astrophys. 698, A115 (2025).
Manfroid, J. et al. The CN isotopic ratios in comets. Astron. Astrophys. 503, 613–624 (2009).
Biver, N., Dello Russo, N., Opitom, C. & Rubin, M. in Comets III (eds Meech, K. J. et al.) 459–498 (Univ. Arizona Press, 2024).
Altwegg, K., Balsiger, H. & Fuselier, S. A. Cometary chemistry and the origin of icy Solar System bodies: the view after Rosetta. ARA&A 57, 113–155 (2019).
Cordiner, M. A. et al. Evidence for surprising heavy nitrogen isotopic enrichment in comet 46P/Wirtanen’s hydrogen cyanide. Planet. Sci. J. 5, 221 (2024).
Moulane, Y. et al. Activity and composition of the hyperactive comet 46P/Wirtanen during its close approach in 2018. Astron. Astrophys. 670, A159 (2023).
Fray, N., Bénilan, Y., Cottin, H., Gazeau, M.-C. & Crovisier, J. The origin of the CN radical in comets: a review from observations and models. Planet. Space Sci. 53, 1243–1262 (2005).
Sipilä, O. et al. Combined model for 15N, 13C, and spin-state chemistry in molecular clouds. Astron. Astrophys. 678, A120 (2023).
Langer, W. D., Graedel, T. E., Frerking, M. A. & Armentrout, P. B. Carbon and oxygen isotope fractionation in dense interstellar clouds. Astrophys. J. 277, 581–604 (1984).
Rubin, M. et al. Evidence for depletion of heavy silicon isotopes at comet 67P/Churyumov–Gerasimenko. Astron. Astrophys. 601, A123 (2017).
Hässig, M. et al. Isotopic composition of CO2 in the coma of 67P/Churyumov–Gerasimenko measured with ROSINA/DFMS. Astron. Astrophys. 605, A50 (2017).
Altwegg, K. et al. Molecule-dependent oxygen isotopic ratios in the coma of comet 67P/Churyumov–Gerasimenko. Mon. Not. R. Astron. Soc. 498, 5855–5862 (2020).
Ritchey, A. M., Federman, S. R. & Lambert, D. L. The C14N/C15N ratio in diffuse molecular clouds. Astrophys. J. 804, L3 (2015).
Marty, B., Chaussidon, M., Wiens, R. C., Jurewicz, A. J. G. & Burnett, D. S. A 15N-poor isotopic composition for the Solar System as shown by Genesis solar wind samples. Science 332, 1533–1536 (2011).
Jensen, S. S. et al. Fractionation in young cores: direct determinations of nitrogen and carbon fractionation in HCN. Astron. Astrophys. 685, A149 (2024).
Colzi, L. et al. CHEMOUT: CHEMical complexity in star-forming regions of the OUTer Galaxy. III. Nitrogen isotopic ratios in the outer Galaxy. Astron. Astrophys. 667, A151 (2022).
Guzmán, V. V., Öberg, K. I., Huang, J., Loomis, R. & Qi, C. Nitrogen fractionation in protoplanetary disks from the H13CN/HC15N ratio. Astrophys. J. 836, 30 (2017).
Wilson, T. L. Isotopes in the interstellar medium and circumstellar envelopes. Rep. Prog. Phys. 62, 143–185 (1999).
Lisse, C. M. et al. SPHEREx discovery of strong water ice absorption and an extended carbon dioxide coma in 3I/ATLAS. Res. Notes AAS 9, 242 (2025).
Hopkins, M. J., Lintott, C., Bannister, M. T., Mackereth, J. T. & Forbes, J. C. The Galactic interstellar object population: a framework for prediction and inference. Astron. J. 166, 241 (2023).
Hopkins, M. J. et al. From a different star: 3I/ATLAS in the context of the Ōtautahi–Oxford interstellar object population model. Astrophys. J. 990, L30 (2025).
Taylor, A. G. & Seligman, D. Z. The kinematic age of 3I/ATLAS and its implications for early planet formation. Astrophys. J. 990, L14 (2025).
Kobayashi, C., Karakas, A. I. & Umeda, H. The evolution of isotope ratios in the Milky Way Galaxy. Mon. Not. R. Astron. Soc. 414, 3231–3250 (2011).
Timmes, F. X., Woosley, S. E. & Weaver, T. A. in Nuclei in the Cosmos III (eds Busso, M. et al.) Vol. 327, 543 (AIP, 1995).
Yan, Y. T. et al. Direct measurements of carbon and sulfur isotope ratios in the Milky Way. Astron. Astrophys. 670, A98 (2023).
Milam, S. N., Savage, C., Brewster, M. A., Ziurys, L. M. & Wyckoff, S. The 12C/13C isotope gradient derived from millimeter transitions of CN: the case for Galactic chemical evolution. Astrophys. J. 634, 1126–1132 (2005).
Pagel, B. E. J. & Edmunds, M. G. Abundances in stellar populations and the interstellar medium in galaxies. Annu. Rev. Astron. Astrophys 19, 77–113 (1981).
Lee, S., Nomura, H. & Furuya, K. Carbon isotope chemistry in protoplanetary disks: effects of C/O ratios. Astrophys. J. 969, 41 (2024).
Bedell, M. et al. The chemical homogeneity of Sun-like stars in the solar neighborhood. Astrophys. J. 865, 68 (2018).
Nissen, P. E. High-precision abundances of elements in solar twin stars. Trends with stellar age and elemental condensation temperature. Astron. Astrophys. 579, A52 (2015).
Bergin, E. A. et al. The carbon isotopic ratio and planet formation. Astrophys. J. 965, 147 (2024).
Maggiolo, R., Dhooghe, F., Gronoff, G. P., de Keyser, J. & Cessateur, G. Interstellar Comet 3I/ATLAS: evidence for Galactic cosmic-ray processing. Astrophys. J. 996, L34 (2026).
Hui, M.-T., Jewitt, D., Mutchler, M. J., Agarwal, J. & Kim, Y. Nucleus and postperihelion activity of interstellar object 3I/ATLAS observed by the Hubble Space Telescope. Astrophys. J. 999, L37 (2026).
van Dokkum, P. G. Cosmic-ray rejection by Laplacian edge detection. PASP 113, 1420–1427 (2001).
Hutsemékers, D., Manfroid, J., Jehin, E., Zucconi, J.-M. & Arpigny, C. The 16OH/18OH and OD/OH isotope ratios in comet C/2002 T7 (LINEAR). Astron. Astrophys. 490, L31–L34 (2008).
Villanueva, G. L. et al. A sensitive search for deuterated water in comet 8p/Tuttle. Astrophys. J. 690, L5–L9 (2009).
Bockelée-Morvan, D. et al. Large excess of heavy nitrogen in both hydrogen cyanide and cyanogen from comet 17P/Holmes. Astrophys. J. 679, L49 (2008).
Biver, N. et al. Isotopic ratios of H, C, N, O, and S in comets C/2012 F6 (Lemmon) and C/2014 Q2 (Lovejoy). Astron. Astrophys. 589, A78 (2016).
Manfroid, J. et al. Isotopic abundance of nitrogen and carbon in distant comets. Astron. Astrophys. 432, L5–L8 (2005).
Hutsemékers, D. et al. Isotopic abundances of carbon and nitrogen in Jupiter-family and Oort Cloud comets. Astron. Astrophys. 440, L21–L24 (2005).
Arpigny, C. et al. Anomalous nitrogen isotope ratio in comets. Science 301, 1522–1525 (2003).
Yang, B. et al. Isotopic ratios in outbursting comet C/2015 ER61. Astron. Astrophys. 609, L4 (2018).
Bockelée-Morvan, D. et al. A multi-wavelength simultaneous study of the composition of the Halley-family comet 8P/Tuttle at the VLT. In Asteroids, Comets, Meteors 2008 LPI Contribution No. 1405 (ed. LPI Editorial Board) 8190 (Lunar and Planetary Institute, 2008).
Jehin, E. et al. Deep impact: high-resolution optical spectroscopy with the ESO VLT and the Keck I telescope. Astrophys. J. 641, L145–L148 (2006).
Moulane, Y. et al. Photometry and high-resolution spectroscopy of comet 21P/Giacobini–Zinner during its 2018 apparition. Astron. Astrophys. 640, A54 (2020).
Jehin, E. et al. Optical spectroscopy of the B and C fragments of comet 73P/Schwassmann–Wachmann 3 at the ESO VLT. In Asteroids, Comets, Meteors 2008 LPI Contribution No. 1405 (ed. LPI Editorial Board) 8319 (Lunar and Planetary Institute, 2008).
Jehin, E. et al. A multi-wavelength study with the ESO VLT of comet 103P/Hartley2 at the time of the EPOXI encounter. In EPSC-DPS Joint Meeting 2011 Vol. 6, EPSC-DPS2011-1463 (2011).
Jehin, E. et al. The anomalous 14N/15N ratio in comets 122P/1995 S1 (de Vico) and 153P/2002 C1 (Ikeya–Zhang). Astrophys. J. 613, L161–L164 (2004).
Shinnaka, Y. et al. Nitrogen isotopic ratios of NH2 in comets: implication for 15N-fractionation in cometary ammonia. Mon. Not. R. Astron. Soc. 462, S195–S209 (2016).
Shinnaka, Y. et al. High-dispersion spectroscopic observations of comet C/2012 S1 (ISON) with the Subaru Telescope. In AAS/Division for Planetary Sciences Meeting Abstracts Vol. 46, 209.14 (American Astronomical Society, 2014).
Rousselot, P., Jehin, E., Manfroid, J. & Hutsemékers, D. The 12C2/12C13C isotopic ratio in comets C/2001 Q4 (NEAT) and C/2002 T7 (LINEAR). Astron. Astrophys. 545, A24 (2012).
Shinnaka, Y. & Kawakita, H. Nitrogen isotopic ratio of cometary ammonia from high-resolution optical spectroscopic observations of C/2014 Q2 (Lovejoy). Astron. J. 152, 145 (2016).
Stawikowski, A. & Greenstein, J. L. The isotope ratio C12/C13 in a comet. Astrophys. J. 140, 1280 (1964).
Owen, T. The isotope ratio 12C/13C in comet Tago-Sato (1969g). Astrophys. J. 184, 33–44 (1973).
Danks, A. C., Lambert, D. L. & Arpigny, C. The 12C/13C ratio in comet Kohoutek (1973f). Astrophys. J. 194, 745–751 (1974).
Vanysek, V. Carbon isotope ratio in comets and interstellar matter. In IAU Colloquium 39: Comets, Asteroids, Meteorites: Interrelations, Evolution and Origins (ed. Delsemme, A. H.) 499–503 (Univ. Toledo, 1977).
Wyckoff, S., Kleine, M., Peterson, B. A., Wehinger, P. A. & Ziurys, L. M. Carbon isotope abundances in comets. Astrophys. J. 535, 991–999 (2000).
Lambert, D. L. & Danks, A. C. High-resolution spectra of C2 Swan bands from comet West 1976 VI. Astrophys. J. 268, 428–446 (1983).
Lis, D. C. et al. Spectroscopic observations of Comet C/1996 B2 (Hyakutake) with the Caltech Submillimeter Observatory. Icarus 130, 355–372 (1997).
Wyckoff, S. et al. The 12C/13C abundance ratio in comet Halley. Astrophys. J. 339, 488 (1989).
Jaworski, W. A. & Tatum, J. B. Analysis of the Swings effect and Greenstein effect in comet P/Halley. Astrophys. J. 377, 306 (1991).
Kleine, M., Wyckoff, S., Wehinger, P. A. & Peterson, B. A. The carbon isotope abundance ratio in comet Halley. Astrophys. J. 439, 1021 (1995).
Jewitt, D., Matthews, H. E., Owen, T. & Meier, R. The 12C/13C, 14N/15N and 32S/34S isotope ratios in comet Hale–Bopp (C/1995 O1). Science 278, 90–93 (1997).
Ziurys, L. M. et al. Cyanide chemistry in comet Hale–Bopp (C/1995 O1). Astrophys. J. 527, L67–L71 (1999).
Cordiner, M. A. et al. ALMA autocorrelation spectroscopy of comets: the HCN/H13CN ratio in C/2012 S1 (ISON). Astrophys. J. 870, L26 (2019).
Rousselot, P. et al. 12CO+ and 13CO+ fluorescence models for measuring the 12C/13C isotopic ratio in comets. Astron. Astrophys. 683, A50 (2024).
Müller, D. R. et al. High D/H ratios in water and alkanes in comet 67P/Churyumov–Gerasimenko measured with Rosetta/ROSINA DFMS. Astron. Astrophys. 662, A69 (2022).
Zhang, K., Bergin, E. A., Blake, G. A., Cleeves, L. I. & Schwarz, K. R. Mass inventory of the giant-planet formation zone in a solar nebula analogue. Nat. Astron. 1, 0130 (2017).
Yoshida, T. C., Nomura, H., Furuya, K., Tsukagoshi, T. & Lee, S. A new method for direct measurement of isotopologue ratios in protoplanetary disks: a case study of the 12CO/13CO ratio in the TW Hya disk. Astrophys. J. 932, 126 (2022).

