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

Article

关键词: EMISSION;    SPECTRUM;    SPECTROSCOPY;    SOLAR;    GAS;   

DOI  :  10.1038/s41586-021-03485-4

来源: SCIE

【 摘 要 】

On 31 August 2019, an interstellar comet was discovered as it passed through the Solar System (2I/Borisov). On the basis of initial imaging observations, 2I/Borisov seemed to be similar to ordinary Solar System comets(1,2)-an unexpected characteristic given the multiple peculiarities of the only known previous interstellar visitor, 1I/'Oumuamua(3-6). Spectroscopic investigations of 2I/Borisov identified the familiar cometary emissions from CN (refs. (7-9)), C-2 (ref. (10)), O i (ref. (11)), NH2 (ref. (12)), OH (ref. (13)), HCN (ref. (14)) and CO (refs. (14,15)), revealing a composition similar to that of carbon monoxide-rich Solar System comets. At temperatures greater than 700 kelvin, comets also show metallic vapours that are produced by the sublimation of metal-rich dust grains(16). Observation of gaseous metals had until very recently(17) been limited to bright sunskirting and sungrazing comets(18-20) and giant star-plunging exocomets(21). Here we report spectroscopic observations of atomic nickel vapour in the cold coma of 2I/Borisov at a heliocentric distance of 2.322 astronomical units-equivalent to an equilibrium temperature of 180 kelvin. Nickel in 2I/Borisov seems to originate from a short-lived nickel-containing molecule with a lifetime of 340(-200)(+260) seconds at 1 astronomical unit and is produced at a rate of 0.9 +/- 0.3 x 10(22) atoms per second, or 0.002 per cent relative to OH and 0.3 per cent relative to CN. The detection of gas-phase nickel in the coma of 2I/Borisov is in line with the recent identification of this atom-as well as iron-in the cold comae of Solar System comets(17).

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