Characterization of the Nucleus, Morphology, and Activity of Interstellar Comet 2I/Borisov by Optical and Near-infrared GROWTH, Apache Point, IRTF, ZTF, and Keck Observations

Abstract

We present visible and near-infrared (NIR) photometric and spectroscopic observations of interstellar object (ISO) 2I/Borisov taken from 2019 September 10 to 2019 December 20 using the GROWTH, the Apache Point Observatory Astrophysical Research Consortium 3.5 m, and the NASA Infrared Telescope Facility 3.0 m combined with pre-and postdiscovery observations of 2I obtained by the Zwicky Transient Facility from 2019 March 17 to 2019 May 5. Comparison with imaging of distant solar system comets shows an object very similar to mildly active solar system comets with an outgassing rate of ∼10 27 mol s −1. The photometry, taken in filters spanning the visible and NIR range, shows a gradual brightening trend of ∼0.03 mag day −1 since 2019 September 10 UTC for a reddish object becoming neutral in the NIR. The light curve from recent and prediscovery data reveals a brightness trend suggesting the recent onset of significant H 2 O sublimation with the comet being active with super volatiles such as CO at heliocentric distances >6 au consistent with its extended morphology. Using the

Early Observations of the Interstellar Comet 2I/Borisov

“…Nevertheless, even with this upper limit, the size and the mass of 2I/Borisov are in similar ranges of the comets in the solar system [4,6]. We note that our independent observations lead to the results similar to [1,[7][8][9]. It has been reported that the reflectance spectrum of 2I/Borisov is similar to that of comets and D-type asteroids seen in the solar system [10].…”

Tails: Chasing Comets with the Zwicky Transient Facility and Deep Learning

“…Containing the original materials from when the solar system first formed, comets provide a unique insight into the distant past of our solar system. The recent discovery of the first interstellar comet 2I/Borisov by amateur astronomer Gennadiy Borisov predictably sparked much excitement and enthusiasm among astronomers and the general public alike (e.g., Bolin et al 2020;Fitzsimmons et al 2019;Guzik et al 2020). Such objects could potentially provide important information on the formation of other stellar systems.…”

Constraints on the spin-pole orientation, jet morphology, and rotation of interstellar comet 2I/Borisov with deep HST imaging

“…The second interstellar object, 2I/Borisov (hereafter 2I), has had a morphological appearance similar to Solar system comets ever since its discovery (Guzik et al 2020;Bolin et al 2020a). Cometary gas measurements have revealed CO (Bodewits et al 2020;Cordiner et al 2020), and [O I] resulting from photodissociation of H 2 O (McKay et al 2019;Crovisier et al 2019), and the typical visiblewavelength daughter species (e.g.…”

“…The colour and activity of 2I have been revealed to be similar to that of Solar system comets. Visible to near-infrared photometry and spectra of the comet are reddish to neutral suggesting the presence of refractory organics and water-ice common in comets (de León et al 2019;Bolin et al 2020a;Yang et al 2020). Additionally, its activity has been revealed by long-term light curve trending to be driven by supervolatiles such as CO/CO 2 far from the Sun, with the addition of H 2 O-driven activity as the comet crossed inside 3-4 au on its way to a ∼2 au perihelion distance (Bolin et al 2020a;Ye et al 2019;Cremonese et al 2020).…”