Researchers have determined that the comet, known as 2I / Borisov, is more virgin and unalterable than any of the comets observed in our solar system. The dust around the comet is also intriguingly different from that around other comets.
The comet was discovered by amateur astronomer Gennady Borisov and astronomers confirmed that it originated outside our solar system.
However, previous observations of the interstellar comet suggested that it was more similar to those in our solar system and little was known about the comet’s core. A comet nucleus is the main, solid component of a comet made up of rock, dust, and frozen gases.
The comet’s new observations, made with the Very Large Telescope at the Southern European Observatory in Chile, helped astronomers measure the polarization of light in the comet’s dust grains.
Science is similar to how polarized sunglasses filter glare and brightness. In this case, astronomers observed how sunlight was polarized or filtered by the comet’s dust to know the comet’s physical properties.
The use of this technique, known as polarimetry, which is also used to study the comets of our solar system, allowed a comparison between 2I / Borisov and other known comets.
Polarimetry was first used more than 200 years ago to observe the “Great Comet of 1819” by French astronomer François Arago. It is now used to study and observe the first known comet that originated outside our solar system, said Stefano Bagnulo, lead author of the Nature Communications study and astronomer at the Armagh Observatory and Planetarium in Northern Ireland.
The polarization of comet 2I / Borisov was much higher than that of comets in our solar system, with the exception of comet C / 1995 O1, also known as Hale-Bopp. Comet Hale-Bopp was very visible to the naked eye in the late 1990s and was considered to be largely virgin before passing through our 1997 sun. This meant that Hale-Bopp was not largely unaltered by the cloud. of comet gas and dust originally formed, which is the same as our solar system also originated 4.5 billion years ago.
What makes the interstellar comet unique is that its polarized light is uniform, which makes it more virgin. Astronomers believe this suggests that 2I / Borisov has remained calm since it formed, until it flew through our sun in 2019.
“Comet 2I / Borisov probably never passed close to the Sun or any other star and may represent the first truly virgin comet ever observed,” the authors wrote in their study.
This means that 2I / Borisov carries unchanged information about the gas and dust that originally formed the comet.
“It looks like 2I / Borisov originated in an environment not too different from our first solar system,” Bagnulo said. “So instead of saying anything about comets in general, Comet 2I / Borisov tells us that other solar systems may not be as different from our own solar system.”
Astronomers still want to understand more about the nature of the dust the comet expels. Bagnulo noted that the scientific operations of the Southern European Observatory were suspended due to Covid in April and May 2020, which might provide more information.
“Comets that never passed close to the sun are particularly interesting because their material (presumably) is not contaminated by solar radiation and wind and, as such, carry information about the environment of our initial solar system,” said Bagnulo. “There is even a small possibility that the target of this mission will be another interstellar comet, if such an exotic object is discovered at the right time.”
Another solar system
The origin story of comet 2I / Borisov can be told by its dust grains.
When astronomers used the Southern European Observatory’s Very Large Telescope and the Atacama Large Millimeter / Submillimeter Telescope Array in Chile, they were able to gather information about the comet’s past.
“Our observations suggest that the comet’s materials are not evenly distributed. Instead, the comet is made up of components that have different compositions and form in different places,” said Bin Yang, lead author of the study. Nature Astronomy and astronomer at the Southern European Observatory in Chile.
The coma, or dust envelope that surrounds the comet’s core, actually contains compact or millimeter-sized pebbles. These grains were also previously detected in Comet Hale-Bopp.
The water and carbon monoxide content of the comet also seemed to change in a very noticeable way as it approached our sun.
Combined, this information suggests that the comet is made up of a potpourri of materials from different parts of its original planetary system.
As in our own solar system, the presence of giant planets and their gravity may have caused this mixture, removing material throughout the system.
“Although the most common planets in other exoplanetary systems appear to be super-Earths and mini-Neptunes, our study suggests the presence of giant planets in the 2I / Borisov home system,” the authors wrote in their study.
Yang predicts that future telescopes, both terrestrial and space, will allow scientists to detect more interstellar objects as they pass through our corner of the universe.
“Imagine the luck we had of a comet from a system light years away that just made a trip to our door by chance,” Yang said.