Researchers have determined that the comet, known as 2I / Borisov, is more pristine and unchanged 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 have confirmed that it comes from outside our solar system.
However, previous observations of the interstellar comet have suggested that it is more like that in our solar system, and that little is known about the core of the comet. A comet nucleus is the main, solid component of a comet that consists of rock, dust, and frozen gases.
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.
The science is similar to how polarized sunglasses filter gloss and brightness. In this case, astronomers observed how sunlight was polarized or filtered by the comet’s dust to learn the physical properties of the comet.
Using this technique, known as polarimetry, which is also used to study comets in our solar system, a comparison between 2I / Borisov and other known comets could be compared.
Polarimetry was first used more than 200 years ago to observe the “Great Comet of 1819” by the French astronomer François Arago. It is now being used to study and observe the first known comet to have formed 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 is considered largely untouched before passing by our sun in 1997. This meant that Hale-Bopp was largely unchanged from the cloud of gas and dust from which the comet originally formed, these are the same things from which our solar system also originated 4.5 billion years ago.
What makes the interstellar comet unique is that its polarized light is uniform, making it more pristine. Astronomers believe this indicates that 2I / Borisov remained undisturbed since it formed – until it flew to our sun in 2019.
“Comet 2I / Borisov probably never passed near the sun or any other star, and is possibly the first true pristine comet ever observed,” the authors write in their study.
This means that 2I / Borisov carries unchanged information about the gas and dust that originally formed the comet.
“It seems like 2I / Borisov originated in an environment that is not too different from our early solar system,” Bagnulo said. “Instead of telling us something about comets in general, comet 2I / Borisov therefore tells us that other solar systems may not be as different from our own solar system.”
Astronomers want to understand even more about the nature of the dust emitted by the comet. Bagnulo noted that scientific activities at the European Southern Observatory were suspended due to Covid in April and May 2020, which may have provided more of the information.
“Comets that have never passed near the sun are particularly interesting because their material (presumably) was not polluted by solar radiation and wind, and as such contains information about the environment of our early solar system,” Bagnulo said. “There is even a small chance that the goal of the mission is another interstellar comet, if such an exotic object is discovered at the right time.”
Another solar system
Comet 2I / Borisov’s origin story can be told through its dust grains.
When astronomers used the European Southern Observatory’s Very Large Telescope and the Atacama Large Millimeter / submillimeter series of telescopes in Chile, they were able to compile information about the comet’s past.
“Our observations indicate that material in the comet is not uniformly distributed. Instead, the comet consists of components that have different compositions and are formed in different places,” said Bin Yang, lead author of the Nature Astronomy study and said an astronomer at the European Southern Observatory. in Chile.
The coma, or dust envelope that surrounds the core of the comet, actually contains compact stones or grains millimeters in size. These grains have also been previously detected in the comet Hale-Bopp.
The comet’s water and carbon monoxide content also appears to change in a very striking way as it approaches our sun.
This information together indicates that the comet consists of a potpourri of materials from different parts of its original planetary system.
As in our own solar system early on, the presence of giant planets and their severity may have caused this mixture, which generated material throughout the system.
“Although most planets in other exoplanetary systems appear to be super-Earth and mini-Neptunes, our study indicates the presence of giant planets in the home system of 2I / Borisov,” the authors write in their study.
Yang foresees that future telescopes, both on Earth and in space, will enable scientists to detect more interstellar objects as they move through our corner of the universe.
“Imagine how lucky we were that a comet from a light-year system simply happened to be on our doorstep,” Yang said.