Researchers have determined that the comet, known as 2I / Borisov, is pristine and unaltered than any comet seen 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 came from outside our solar system.
However, previous observations of the interstellar comet suggested that it was more like the one in our solar system, and that 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.
New observations of the comet, taken using the Very Large Telescope at the European Southern Observatory in Chile, helped astronomers measure the polarization of light in the comet’s dust particles.
The science is similar to how polarized sunglasses filter glare and clarity. In this case, astronomers observed how sunlight was polarized or filtered through the comet’s dust to learn more about the comet’s physical properties.
This technique – known as polarimetry, which is also used to study comets in 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 the French astronomer François Arago. Now it is used to study and observe the first known comet to originate outside our solar system, said Stefano Bagnulo, lead research author of the Nature Communications study and astronomer at the Armagh Observatory and Planetarium in Northern Ireland.
The polarization for 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 highly visible to the naked eye in the late 1990s and was considered largely untouched before passing through our sun. 1997. That meant that Hale-Bopp was largely unchanged by the cloud of gas and dust that originally formed the comet, the same material that our solar system formed 4.5 billion years ago.
What makes the interstellar comet unique is that the polarized light is uniform, making it more pristine. Astronomers think this suggests that 2I / Borisov has remained undisturbed since its inception – until it flew through our sun in 2019.
“Comet 2I / Borisov has most likely never passed close to the sun or any other star and may represent the first truly pristine comet ever observed,” the authors wrote in their study.
That means that 2I / Borisov contains unaltered information about the gas and dust that originally formed the comet.
“It appears that 2I / Borisov originated in an environment not very different from our early solar system,” said Bagnulo. “That’s why Comet 2I / Borisov, instead of telling us about comets in general, tells us that other solar systems are not that different from our own solar system.”
Astronomers still want to know more about the nature of the dust emitted by the comet. Bagnulo noted that scientific operations at the European Southern Observatory were suspended in April and May 2020 due to Covid, which may have provided more of that information.
“Comets that never got close to the Sun are particularly interesting because their material is (presumably) not contaminated by solar radiation and wind, and as such they contain information about the environment of 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 origin story of Comet 2I / Borisov can be told from the dust particles.
When astronomers used the European Southern Observatory’s Very Large Telescope and the Atacama Large Millimeter / submillimeter Array of telescopes in Chile, they were able to gather information about the comet’s past.
“Our observations suggest that materials in the comet are not evenly distributed. Instead, the comet consists of components with different compositions and formed in different places,” said Bin Yang, lead author of the Nature Astronomy study and an astronomer at the European Southern Observatory. . in Chile.
The coma, or dust envelope that surrounds the comet’s core, actually contains compact pebbles, or millimeter-sized grains. These beads were also previously detected in Comet Hale-Bopp.
The comet’s water and carbon monoxide content also seemed to change in a very noticeable way as it approached our sun.
Combined, this information suggests that the comet is made from a potpourri of materials from different parts of its native planetary system.
As in our own solar system in the beginning, the presence of giant planets and their gravity may have caused this mixing, pushing up material throughout the system.
“While the most abundant planets in other exoplanetary systems appear to be super-Earth and mini-Neptune, our study suggests the presence of giant planets in the 2I / Borisov home system,” the authors wrote in their study.
Yang expects future telescopes, both on the ground and in 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 just accidentally drove to our door,” said Yang.