The European Southern Observatory Very Large Telescope has performed new observations of comet 2l/Borisov. It’s only the second interstellar visitor ever detected in our Solar System. The ESO’s observations have also indicated that 2l/Borisov is one of the most pristine comets ever observed.
Astronomers believe 2l/Borisov most likely never passed close to a star, meaning it’s an undisturbed relic of the cloud of gas and dust that it originally formed from. Amateur astronomer Gennady Borisov discovered 2l/Borisov in August 2019 and a few weeks later was determined to have come from outside our solar system. Researchers investigating the comet used the VLT FORS2 instrument to study 2l/Borisov using a technique called polarimetry.
The technique is commonly used to study comets and other small bodies in the solar system and allowed the researchers to compare 2l/Borisov with comets in the local solar system. What the team discovered was that 2l/Borisov had polarimetric properties that were distinct from those of comets in our solar system, with the exception of Hale-Bopp, which was one of the most pristine comets ever seen by astronomers.
Hale-Bopp is believed to have only passed by the sun one time before entering public interest in the late 1990s. Researchers analyzed the polarization and the color of 2l/Borisov to determine that it was more pristine than Hale-Bopp. 2l/Borisov contained untarnished signatures of the cloud of gas and dust it formed from.
Researchers say that since the two comets were remarkably similar, it suggested that the environment 2l/Borisov originated in wasn’t so different in composition from the early solar system. Researchers believe that the two comets likely formed in very similar conditions.