The International Astronomical Union approved the official name for the first interstellar comet, which in August this year was discovered by the Crimean astronomer Gennady Borisov. Now the object is assigned the name 2I / Borisov, which reflects extra-solar origin, as well as the second serial number in the group of such bodies after Oumuamua.
In addition to stars and planets, the solar system includes many small bodies, such as asteroids and comets. Asteroids are rocky or metallic bodies that are mainly located in the main belt, located between the orbits of Mars and Jupiter, and move in close to circular orbits. The composition of comets includes significant amounts of frozen gases, and their orbits are often very elongated, which is considered an indication of the existence of an extensive Oort cloud on the outskirts of our system.
The orbits of cosmic bodies make it possible to divide them into those connected with the Sun and those who arrived from outside. To do this, use a parameter called eccentricity, which characterizes the elongation of the trajectories: if it is less than unity, then the orbit is closed (circle or ellipse), if it is equal to or more, it is open (parabola or hyperbola). Usually, the orbital parameters are determined with noticeable errors, so only a much larger unit eccentricity is considered evidence of extrasolar origin.
In the entire history of astronomical observations, only two relatively large objects were identified as arriving from other parts of the Galaxy, although the presence of small dust particles from interstellar space between the planets of the solar system has been proven.
The Oumuamua object opened in 2017 was the first body. Scientists still argue about its exact nature, since it showed the properties of both asteroids and comets. Its official name is 1I / Oumuamua: I / means extra-solar origin, and the number 1 is the first serial number in the list of objects of this class.
On August 30, astronomer Gennady Borisov, an employee of the Crimean Astrophysical Observatory, published observational data on a new body, from which an extremely large eccentricity of 3.07 followed. After confirmation of the discovery by other observatories, which excluded the possibility of errors in observations and interpretations, the discovery was officially established. Since the object looked like a comet in appearance, it automatically received the name C / 2019 Q4 (Borisov).
To date, the orbit of this comet is known quite accurately and clearly speaks of extrasolar origin, which makes it the second known body with a similar trajectory. This allowed the International Astronomical Union to officially approve a new name for the object – 2I / Borisov. In this case, the tradition of naming comets according to their discoverers was used.
2I / Borisov will perihelion (the closest trajectory to the Sun) on December 7, 2019. At this moment, there will be about two astronomical units between the comet and star, and approximately the same will separate it from the Earth. It is expected that in December and January it will be a bright object in the sky of the Southern Hemisphere: astronomers expect close passage of the object, which will allow it to be examined in detail. Also, the 2I / Borisov trajectory in this sense is better than the 1I / Oumuamua’s trajectory, so it can be explored longer.
Via | IOU