Discovered last year, comet 2I / Borisov became only the second object in the solar system, whose interstellar origin has been reliably confirmed by astronomers. The tailed guest has already passed the perihelion of the orbit and is now leaving the vicinity of the Sun, moving in the direction of the southern constellation of the Telescope. But where did she come from?
The first attempt to find the interstellar traveler's home system was made by a team of Polish astronomers. After analyzing the data from the Gaia telescope, they determined that about one million years ago, the comet passed at a distance of 5 light years from the pair of red dwarfs Kruger 60. Calculations showed that the relative speed of the object relative to the system was only 3.43 km / s. Therefore, astronomers have suggested that the comet may have originated from an analogue of the Oort cloud around Kruger 60. However, many scientists have questioned this possibility, since the distance of 5 light years is too great for such a structure.
Therefore, a team of astronomers from Europe and the United States conducted a new, more detailed study. Scientists also used information collected by the Gaia telescope, as well as updated data on the trajectory of the comet. Modeling revealed 14 stellar systems with which Borisov's comet approached at a distance of less than 1 parsec (3.26 light years).
The greatest interest among researchers was caused by the star Ross 573. It is a solitary red dwarf located at a distance of 60 light-years from the Sun. Modeling showed that 910 thousand years ago, the interstellar traveler passed at a distance of only 0.22 light years from the star. This is quite enough for Borisov's comet to originate from an analogue of the Oort cloud of this system. Moreover, the calculations carried out by the researchers showed that such close encounters between the Borisov comet and the stars should, on average, occur only once every 120 million years. At the same time, the researchers have one serious argument against the fact that Ross 573 is really “the homeland »Borisov's comet. Calculations indicate that the speed of the body relative to the red dwarf was 23 km / s. This is a lot. For comparison, the maximum possible speed of an ejection of a comet from an analogue of the solar system would be only 17.4 km / s.
To gain a speed of 23 km / s, Borisov's comet had to pass very close to some object with a mass significantly exceeding the mass of Jupiter - a brown or red dwarf. However, so far, astronomers have not been able to find any major companions in Ross 573. So, perhaps this is still a coincidence, and during its wanderings along the Milky Way, the comet simply made a close flyby of this system. Another possibility is that Ross 573 has moved closer to another star in the recent past. The gravitational perturbations accompanying this event led to the ejection of objects from the surrounding accumulation of ice bodies - including the comet Borisov.