The researchers determined that the comet, known as 2I / Borisov, is cleaner and unaltered than any of the comets that have been 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 have confirmed that it came from outside our solar system.
However, previous observations of the interstellar comet have suggested that it is more similar to those found in our solar system and little is known about the comet’s core. A comet nucleus is the main solid component of a comet made up of rocks, dust and frozen gases.
The new observations of the comet, made using the very large Telescope of the European Southern Observatory in Chile, helped astronomers measure the polarization of light in the comet’s dust grains.
Science is similar to how polarized sunglasses filter out glow and shine. In this case, astronomers observed how sunlight was polarized or filtered by comet dust to learn about the comet’s physical properties.
The use of this technique – known as polarimetry, which is also used to study comets in our solar system – has 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 to be born outside our solar system, said Stefano Bagnulo, lead author of the study Nature Communications and astronomer at the Armagh Observatory and Planetarium in Northern Ireland.
The polarization for comet 2I / Borisov was much larger than that of comets in our solar system, except for comet C / 1995 O1 – also known as Hale-Bopp. Comet Hale-Bopp was highly visible to the naked eye in the late 1990s and was considered to be largely clean before passing our 1997 sun. This meant that Hale-Bopp was largely unaltered. of the cloud of gas and dust from which the comet formed, which is the same thing, even our solar system dates back 4.5 billion years.
What makes the interstellar comet unique is that its polarized light is uniform, which makes it cleaner. Astronomers believe this suggests that 2I / Borisov has remained undisturbed since it formed – until it flew near our sun in 2019.
“Comet 2I / Borisov most likely never passed close to the Sun or any other star and may be the first truly clean 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 seems that 2I / Borisov has its origins in an environment not too different from our early solar system,” Bagnulo said. “Therefore, rather than saying anything about comets in general, Comet 2I / Borisov tells us that other solar systems may not be so different from our own solar system.”
Astronomers still want to understand more about the nature of the dust expelled by the comet. Bagnulo noted that scientific operations at the European Southern Observatory were suspended due to Covid in April and May 2020, which could have provided more information.
“Comets that have never passed close to the sun are particularly interesting because their material is (probably) uncontaminated by solar and wind radiation and, as such, carries information about the environment in our early solar system,” Bagnulo said. “There is even a small chance that the target of that mission will be another interstellar comet, if such an exotic object is discovered at the right time.”
Another solar system
The story of the origin of comet 2I / Borisov can be told by its dust grains.
When astronomers used the very large European Southern Observatory Telescope and the Atacama Matrix of millimeters / submillimeters of large telescopes 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 Astronomy of Nature and astronomer at the European Southern Observatory. in Chile.
The coma or dust cover surrounding the comet’s core actually contains compact pebbles or millimeter-sized grains. These grains were also previously detected in Comet Hale-Bopp.
The water and carbon monoxide content of the comet also changed in a very visible way as it approached our sun.
Combined, this information suggests that the comet is made up of a pool of materials from different parts of its original planetary system.
As in our own solar system from the beginning, the presence of huge planets and their gravity could have caused this mixture, shaking material throughout the system.
“While the most common planets in other exoplanetary systems appear to be super-Earth and mini-Neptunes, our study suggests the presence of giant planets in the origin system of 2I / Borisov,” the authors wrote in their study.
Yang anticipates 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 how lucky we were that a comet from a system light-years away simply made a trip to our door by chance,” Yang said.