Detection of CN gas in Interstellar Object 2I/Borisov

Abstract

The detection of Interstellar Objects passing through the Solar System offers the promise of constraining the physical and chemical processes involved in planetary formation in other extrasolar systems. While the effect of outgassing by 1I/2017 U1 ('Oumuamua) was dynamically observed, no direct detection of the ejected material was made. The discovery of the active interstellar comet 2I/Borisov means spectroscopic investigations of the sublimated ices is possible for this object. We report the first detection of gas emitted by an interstellar comet via the near-UV emission of CN from 2I/Borisov at a heliocentric distance of $r$ = 2.7 au on 2019 September 20. The production rate was found to be Q(CN) = $(3.7\pm 0.4)\times 10^{24}$ s${}^{-1}$, using a simple Haser model with an outflow velocity of 0.5 km s${}^{-1}$. No other emission was detected, with an upper limit to the production rate of C${}_2$ of $4\times 10^{24}$ s${}^{-1}$. The spectral reflectance slope of the dust coma over $3900$ Å $<\lambda <6000$ Å\ is steeper than at longer wavelengths, as found for other comets. Broad band $R_c$ photometry on 2019 September 19 gave a dust production rate of $Af\rho =143\pm 10$ cm. Modelling of the observed gas and dust production rates constrains the nuclear radius to $0.7-3.3$ km assuming reasonable nuclear properties. Overall, we find the gas, dust and nuclear properties for the first active Interstellar Object are similar to normal Solar System comets.

9 pages, 4 figures, accepted for publication in ApJL

References in corpus (4)

• An Observational Upper Limit on the Interstellar Number Density of Asteroids and Comets
• The Natural History of 'Oumuamua
• 1I/2017 U1 (`Oumuamua) is Hot: Imaging, Spectroscopy and Search of Meteor Activity
• Near-UV and optical spectroscopy of comets using the ISIS spectrograph on the WHT

Cited by in corpus (32)

• Initial Characterization of Interstellar Comet 2I/2019 Q4 (Borisov)
• The carbon monoxide-rich interstellar comet 2I/Borisov
• The Nucleus of Interstellar Comet 2I/Borisov
• Solar System Physics for Exoplanet Research
• GJ 273: On the formation, dynamical evolution and habitability of a planetary system hosted by an M dwarf at 3.75 parsec
• Pre-discovery Activity of New Interstellar Comet 2I/Borisov Beyond 5 AU
• Detection of a Water Tracer in Interstellar Comet 2I/Borisov
• Interstellar comet 3I/ATLAS: discovery and physical description
• Detection of Diatomic Carbon in 2I/Borisov
• Exocomets from a Solar System Perspective
• Carbon Chain Depletion of 2I/Borisov
• Outburst and Splitting of Interstellar Comet 2I/Borisov
• Coma Anisotropy and the Rotation Pole of Interstellar Comet 2I/Borisov
• Gaseous atomic nickel in the coma of interstellar comet 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
• A search for the origin of the interstellar comet 2I/Borisov
• The similarity of the interstellar comet 2I/Borisov to solar system comets from high resolution optical spectroscopy
• Capture of interstellar objects: a source of long-period comets
• Activity of the first interstellar comet 2I/Borisov around perihelion: Results from Indian observatories
• X-SHOOTER Spectrum of Comet 3I/ATLAS: Insights into a Distant Interstellar Visitor
• 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*
• Searching for water ice in the coma of interstellar object 2I/Borisov
• FeI and NiI in cometary atmospheres. Connections between the NiI/FeI abundance ratio and chemical characteristics of Jupiter-family and Oort-cloud comets
• Emission from HCN and CH${}_3$OH in comets. Onsala 20-m observations and radiative transfer modelling
• Tails: Chasing Comets with the Zwicky Transient Facility and Deep Learning
• Capture of interstellar objects II: by the Solar system
• Pre-perihelion Monitoring of Interstellar Comet 2I/Borisov
• Near-Discovery SOAR Photometry of the Third Interstellar Object: 3I/ATLAS
• FLAMINGOS-2 infrared photometry of 2I/Borisov
• Ejected from home: C/1980 E1 (Bowell) and C/2024 L5 (ATLAS)
• Dynamical simulation of the Interstellar Comet 3I/ATLAS
• Pre-perihelion Volatile Evolution of Interstellar Comet 3I/ATLAS Indicating Significant Contribution from Extended Source in the Coma