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The first known interstellar comet to visit our solar system is perhaps the most pristine ever found, never passing near a star before visiting ours, researchers say.
In 2019, scientists discovered comet 2I / Borisov as it entered the solar system. The speed and trajectory of the comet revealed that it was a rogue comet from interstellar space, making it the first known interstellar comet and the second known interstellar visitor after 1I / ‘Oumuamua in the shape of a crepe.
Now scientists have discovered two new ways that 2I / Borisov doesn’t look like any known comet. They detailed their results online on March 30 in two studies, one published in the journal Nature Communications and another in the journal Nature Astronomy.
Video: Alien comet Borisov in unbelievably pristine state
Related: ‘Oumuamua and Borisov are just the start of a boon of interstellar objects
In one study, researchers used the European Southern Observatory’s Very Large Telescope to analyze the light scattered by dust grains in the 2I / Borisov coma, i.e. the envelope of gas and dust surrounding its core. Specifically, they looked at the polarization of this light, or the way light waves ripple in space.
All light waves can wave up and down, left and right, or any angle in between. The greater the polarization of light, the more its waves all wave in the same direction.
When a comet passes close to a star, the radiation and winds from that star can alter the material on the comet’s surface, “like our skin when we go to the beach”, Stefano Bagnulo, astronomer at the Observatory of Armagh in Northern Ireland who led the Nature Communications study, told Space.com. This in turn can reduce the polarization of the comet’s coma light.
Scientists found that the light from the 2I / Borisov coma was highly polarized, suggesting that it was more pristine than other comets – that is, its surface was rarely bathed in light and winds. stars. The only comet that previous research found had light as polarized as that of the interstellar visitor was Hale-Bopp, which lit up Earth’s skies in 1997.
“Hale-Bopp has rarely been near the sun,” Bagnulo said. “We believe that before it appeared in 1997, it only did this once, about 4,000 years ago, so the material on its surface, when we observed it, was not. only lightly treated by the sun.
However, the polarization of light through 2 / I Borisov was uniform, while it was not for Hale-Bopp. This suggests that 2 / I Borisov may be the first truly virgin comet ever detected – it may never have ventured near a star before visiting the solar system, making it an intact cloud relic. gas and dust from which it formed.
“The fact that the two comets are remarkably similar suggests that the environment in which 2I / Borisov was born is not that different in composition from the environment in the early solar system”, Alberto Cellino, researcher at the Astrophysical Observatory from Turin in Italy and co-author of the Nature Communications study, said in a press release.
Bagnulo noted that astronomers might have an even better chance of studying a rogue comet in detail before the end of the decade. The European Space Agency plans to launch the Comet Interceptor probe in 2029, a spacecraft that will have the ability to reach another visiting interstellar object, if an object on an appropriate trajectory is discovered, he said.
“Comets that have never passed near the sun are particularly interesting because their material is presumably the same as when our solar system was formed,” Bagnulo said. “It is important to study them.”
In the other study, to gather clues about the comet’s birth and its original system, the researchers analyzed data from the Atacama Large Millimeter / Submillimeter Array (ALMA) in Chile and the Very Large Telescope in Chile. ‘European Southern Observatory.
“We want to know if other planetary systems are forming like ours, but we cannot study these systems at the level of their individual comets – the comets of other planetary systems are just too far away and too small to be seen by our eyes. telescopes. ” Lead author of the study, Bin Yang, a planetary scientist from the European Southern Observatory in Santiago, Chile, told Space.com. “We are very fortunate that a comet from a system light years away has visited us so close.”
Scientists found that the dust in 2I / Borisov’s coma consisted of compact pebbles, 2 millimeters or more wide. In contrast, dust from comets in our solar system is typically made up of irregular, fluffy tufts of material ranging in size from about 0.00008 inches (2 microns) to nearly 39 inches (1 meter) wide.
Previous research has suggested that solar system comets formed in a large region beyond the orbit of infant Neptune, and when giant planets such as Jupiter and Saturn migrated to their current positions, their strong gravity took off. projected these comets to their current locations in the outer solar system.
In contrast, the compact nature of the 2I / Borisov pebbles suggests that they formed in cosmic impacts near the comet’s original star, crushing its material into dense pieces, the researchers found. 2I / Borisov was then thrown into interstellar space by giant planets orbiting its home star.
Going forward, the Vera C. Rubin Observatory in Chile, which is due to open this year, is expected to detect one interstellar object per year. The European Southern Observatory’s Very Large Telescope (ELT), currently under construction in Chile, is expected to shed even more light on these interstellar visitors, Yang said. “The future is quite exciting in terms of detecting and characterizing alien objects from other solar systems,” she said.
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