The Extraordinary Passage of Comet C/2020 F3 NEOWISE: Evidence for Heterogeneous Chemical Inventory in Its Nucleus
Abstract
Upon its discovery in 2020 March, we requested Director Discretionary Time (DDT) at the NASA/IRTF facility to observe comet C/2020 F3 (NEOWISE), with the high-resolution spectrograph iSHELL. The comet approached the Sun, down to 0.3 au, in early 2020 July, providing a spectacular perihelion passage and revealing itself as one of the brightest comets that have appeared in the northern hemisphere in recent decades. Daytime observations with iSHELL/IRTF were performed to study the comet immediately after its perihelion passage, from 9 July to 1 August. In early August, a DDT at Keck Observatory was requested to continue following the comet with NIRSPEC 2.0. We acquired comprehensive high-resolution spectra of the comet as it progressively retreated from perihelion. We detected many cometary emission lines in the (2.8–5.3) μm range, identifying 12 molecular species: 9 primary volatiles (H₂O, HCN, NH₃, CO, C₂H₂, C₂H₆, CH₄, CH₃OH, and H₂CO) and 3 product species (CN, NH₂, OH). In this paper, we present the analysis and discussion of the molecular abundances found in this comet, and we compare them to reference median values for Oort Cloud Comets. Measured molecular mixing ratios showed drastic changes during our observing campaign, which spanned nearly one month from 2020 July 9 to August 6. Here, we provide a detailed discussion of the molecular spatial distributions and their role in identifying the presence of extended sources in the coma. Our investigations provided evidence for the heterogeneous chemical composition of the comet's nucleus.
Additional Information
© 2021. The American Astronomical Society. Received 2021 March 22; revised 2021 July 22; accepted 2021 July 24; published 2021 October 5. This work was supported by the NASA Astrobiology Institute through award (13-13NAI7-0032) to the Goddard Center for Astrobiology and by the NASA's Planetary Science Division Internal Scientist Funding Program (ISFM) through the Fundamental Laboratory Research (FLaRe) work package. M.J.M. was also supported by NASA Goddard's Emeritus Program. Data presented in this work were obtained at the NASA Infrared Telescope Facility, operated by the University of Hawai'i and at the W. M. Keck Observatory, operated as a scientific partnership among Caltech, UCLA, and NASA. We thank the staff of both IRTF and Keck Observatories for their outstanding operational support and valuable technical suggestions during the observing campaign. The authors also thank the Directors of the NASA InfraRed Telescope Facility and the W. M. Keck Observatory for awarding time to our DDT proposals, allowing investigations of this interesting object. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.Attached Files
Published - Faggi_2021_AJ_162_178.pdf
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Additional details
- Eprint ID
- 111375
- Resolver ID
- CaltechAUTHORS:20211012-211827638
- 13-13NAI7-0032
- NASA
- Goddard Space Flight Center
- Created
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2021-10-13Created from EPrint's datestamp field
- Updated
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2021-10-13Created from EPrint's last_modified field
- Caltech groups
- Division of Geological and Planetary Sciences