Ever since 2I/Borisov was first discovered, astronomers have been fascinated with this interstellar comet. With new information being discovered about the comet, experts have confidentially called it the most “pristine” space object that’s ever been studied.
Astronomers don’t think that 2I/Borisov ever traveled close to any star (other than our sun) which means that its composition of gas and dust was completely pure and original. When comets travel close to stars, they can become altered or degraded by the sun’s radiation and heat. Stefano Bagnulo, who is from the Armagh Observatory and Planetarium, Northern Ireland, UK, and who led the new study, stated, “2I/Borisov could represent the first truly pristine comet ever observed.”
The researchers used the FORS2 instrument located on the European Southern Observatory’s (ESO) Very Large Telescope (VLT) to study the comet by a technique called polarimetry. They compared 2I/Borisov to comets that are found in our Solar System. They noticed that it was quite similar to Comet Hale-Bopp that made headlines back in the 1990s when it flew by Earth. Before its journey in the ‘90s, Hale-Bopp was believed to have only passed by our sun once before, meaning that the solar wind and radiation wouldn’t have had much affect on it from a single flyby; therefore it was also considered to be “pristine” but not as much as 2I/Borisov, according to the experts.
Alberto Cellino, who is from the Astrophysical Observatory of Torino, National Institute for Astrophysics (INAF), Italy, and a co-author of the study, explained, “The fact that the two comets are remarkably similar suggests that the environment in which 2I/Borisov originated is not so different in composition from the environment in the early Solar System.”
2I/Borisov provided experts with the unique opportunity of studying its composition and comparing it to comets that originated in our Solar System. Their study was published in Nature Communications where it can be read in full.
Bin Yang (an astronomer at ESO in Chile) and colleagues analyzed data collected from the Atacama Large Millimeter/submillimeter Array (ALMA) and the VLT to study the comet’s dust grains; to find out how it was formed; and to figure out the distant system’s conditions.
The dust that’s present on the comet’s main body (also called coma) contained grains and pebbles that measured at least one millimeter. Furthermore, the water and carbon monoxide significantly changed when it traveled closer to our sun.
Additionally, they believe that the comet was formed from different locations in its system from close to its host star to areas much further away – possibly due to space debris being flung around by powerful gravitational forces from giant exoplanets. It’s possible that this also happened here when our Solar System was first forming. This other new study was published in Nature Astronomy.
Pictures of 2I/Borisov can be seen here.