Gaseous atomic nickel in the coma of interstellar comet 2I/Borisov

Abstract

On 31 August 2019, an interstellar comet was discovered as it passed through the Solar System (2I/Borisov). Based on initial imaging observations, 2I/Borisov appeared to be completely similar to ordinary Solar System comets - an unexpected characteristic after the multiple peculiarities of the only previous known interstellar visitor 1I/'Oumuamua. Spectroscopic investigations of 2I/Borisov identified the familiar cometary emissions from CN, C2, O I, NH2, OH, HCN, and CO, revealing a composition similar to that of carbon monoxide-rich Solar System comets. At temperatures >700 K, comets additionally show metallic vapors produced by the sublimation of metal-rich dust grains. However, due to the high temperature needed, observation of gaseous metals has been limited to bright sunskirting and sungrazing comets and giant star-plunging exocomets. Here we report spectroscopic detection of atomic nickel vapor in the cold coma of 2I/Borisov observed at a heliocentric distance of 2.322 au - equivalent to an equilibrium temperature of 180 K. Nickel in 2I/Borisov seems to originate from a short-lived nickelbearing molecule with a lifetime of $340_{-200}^{+260}$ s at 1 au and is produced at a rate of $0.9\pm 0.3\times 10^{22}$ atoms s${}^{-1}$, or 0.002% relative to OH and 0.3% relative to CN. The detection of gas-phase nickel in the coma of 2I/Borisov is in line with the concurrent identification of this atom (as well as iron) in the cold comae of Solar System comets.

Accepted manuscript with minor post-acceptance corrections

References in corpus (14)

• Techniques and Review of Absolute Flux Calibration from the Ultraviolet to the Mid-Infrared
• Hot Exoplanet Atmospheres Resolved with Transit Spectroscopy (HEARTS) IV. A spectral inventory of atoms and molecules in the high-resolution transmission spectrum of WASP-121 b
• Initial characterization of interstellar comet 2I/Borisov
• The Chemical Composition of an Extrasolar Kuiper-Belt-Object
• Initial Characterization of Interstellar Comet 2I/2019 Q4 (Borisov)
• The carbon monoxide-rich interstellar comet 2I/Borisov
• Unusually High CO Abundance of the First Active Interstellar Comet
• Detection of CN gas in Interstellar Object 2I/Borisov
• Detection of a Water Tracer in Interstellar Comet 2I/Borisov
• High resolution optical spectroscopy of the ${\mathrm{N}}_2$-rich comet C/2016 R2 (PanSTARRS)
• Detection of Diatomic Carbon in 2I/Borisov
• Carbon Chain Depletion of 2I/Borisov
• Visible and near-infrared observations of interstellar comet 2I/Borisov with the 10.4-m GTC and the 3.6-m TNG telescopes
• Interstellar comet 2I/Borisov as seen by MUSE: C${}_2$, NH${}_2$ and red CN detections

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• The Volatile Inventory of 3I/ATLAS as seen with JWST/MIRI
• Cometary science with CUBES
• Refractory elements in the gas phase for comet 67P/Churyumov-Gerasimenko
• Interstellar Ices as Carriers of Supernova Material to the Early Solar System