Comet 2I/Borisov in Comparison with Comets of the Solar System

• Published in: Solar system research 2023-02, Vol.57 (1), p.76-84
• Main Authors: Dorofeeva, V. A., Borisov, G. V., Shustov, B. M.
• Format: Article
• Language: English
• Subjects: Astronomy; Astrophysics and Astroparticles; Astrophysics and Cosmology; Observations and Techniques; Physics; Physics and Astronomy; Planetology
• ISSN: 0038-0946; 1608-3423
• DOI: 10.1134/S0038094623010021

— The brief review summarizes data on the chemical and mineral composition, as well as on the physical properties, of the first extrasolar comet 2I/Borisov, obtained from observations that were carried out from September 2019 to the end of March 2020. It is noted that the qualitative chemical composition of the volatile and mineral components comet 2I/Borisov is similar to the composition of comets in the Solar System, but there are differences that indicate the specific conditions for the formation of its nucleus in a circumstellar gas and dust disk. Different release rates of CO and H 2 O molecules in the vicinity of perihelion indicate the possible heterogeneity of the comet’s nucleus, which was formed from more homogeneous ice blocks, but differing in composition. These constituent blocks could have formed over a wide range of radial distances: from the snow line of H 2 O to the CO snow line. Their accumulation in the comet’s nucleus indicates large-scale mixing of protocometary bodies in the circumstellar disk. No spectra of finely crystalline magnesium silicates were found in cometary coma of 2I/Borisov, which can be interpreted as the absence of a significant amount of gas and dust transfer from the inner hot regions of the disk to the outside, into the zone of formation of protocometary bodies.