Astronomers have published the results of observations of the first interstellar comet is a comet Borisov — with the help of the space telescope Swift. It turned out that at the peak of activity from the surface of the kernel who received up to 30 liters of water in the form of water vapor, and the minimum radius of the nucleus is 370 meters. Article published in the journal The Astrophysical Journal Letters.
Comet 2I/Borisov was discovered August 30, 2019 and is the second known interstellar object after an asteroid 1I/Omwamwi. It is closer to the Sun in December last year, and then began his return to interstellar space. The study of such bodies allows you to learn about the characteristics of the compositions of planetesimals and protoplanetary disks around other stars.
Early observations made it possible to argue that the comet Borisov is very similar for similar objects in the Solar system. However, the analysis of data from space and ground-based telescopes obtained during the approach of the comet to the Sun, showed that it differs significantly in composition from them, in particular, is extremely rich in carbon monoxide. Among observatories followed the comet was a space telescope , Swift, is usually involved in the observation of gamma-ray bursts. On Board is the ultraviolet and optical telescope UVOT, who observed the comet Borisov six times in the period from 27 September 2019, when the comet was 2.56 astronomical units from the Sun, 17 February 2020, when the comet has already passed perihelion and was removed from the sun by 2.54 astronomical units. The objective of the observations was to determine the changes of water vapor in the coma of the comet by observations of the OH radical, produced by photodissociation of water molecules.
It turned out that in the period from 1 November to 1 December 2019 the number of produced molecules in the coma of OH is increased by 50 percent and amounted to 10.7×1026 molecules per second. Such increase more than in the case of dynamically new comets and comets of the Jupiter family. At the peak intensity from the surface of the nucleus of comet Borisov, who received about 30 liters of water per second. After the perihelion passage, on 21 December the rate of generation of water molecules decreased to 4.9×1026 molecules per second, the decline was also much faster than in the case of a previously observed comet of the Solar system. It is assumed that this may be due to erosion of the surface layer, the decay of the nucleus and the changing nature of rotation. Assessment of the amount of water that evaporates from the core during approach to the Sun, gives a value of about 230 million liters. Calculations based on data accumulated by the Observatory, showed that the minimum radius of the nucleus of comet Borisov is 0,37 kilometers, and at least 55 per cent of its surface was active, which is ten times more active areas on comets of the Solar system.
Earlier we talked about how scientists have measured the length of the tail of the comet Borisov and how the increased activity of the comet nucleus led to its destruction.