By comparing our local comet Hale-Bopp with interstellar visitor 2I / Borisov, a team of astronomers has concluded that the interloper is perhaps one of the most inaccurate comets we have ever seen.
“2I / Borisov was able to represent the first truly unequal comet ever observed, ” says Stefano Bagnulo of the Armagh Observatory and Planetarium, Northern Ireland, UK, who led the new study recently published in Nature communication,
Many comets pass through the inner solar system at least once in their lifetime. When they do, they encounter the solar wind and all the other random pieces of microscopic debris floating around. This pollutes them to such an extent that astronomers can determine how many passages a comet has made since it formed.
Comet Hale-Bopp, which attracted stargazers in the late 1990s, was astonishingly pure. Astronomers estimate that it had passed through the sun only once before its entry into the late 20th century.
Using the FORS2 instrument at the European Southern Observatory’s Very Large Telescope in Chile, a team of astronomers studied the interstellar comet 2I / Borisov carefully. That visitor was discovered by amateur astronomer Gennady Borisov in August 2019, and was the second known interstellar intruder for our solar system. The investigation team found that Borisov and Hale-Bopp were remarkably similar.
“The fact that the two comets are strikingly similar suggests that the environment in which 2I / Borisov originated is not so different in composition from the environment in the early solar system,” says Alberto Cellino, a co-author of the study. the Astrophysical Observatory of Turin, National Institute of Astrophysics (INAF), Italy.
Olivier Hainaut, an astronomer at ESO in Germany who studies comets and other near-Earth objects but was not involved in this new study, agrees. “The main result – that 2I / Borisov is not like any other comet except Hale-Bopp – is very strong,” he says, adding: “it is very plausible that they formed in very similar conditions.”
2I / Borisov may not have passed near his parent before he was ejected into interstellar space and made his way to our own solar system.
“The arrival of 2I / Borisov from interstellar space represented the first opportunity to study the composition of a comet from another planetary system and to check whether the material coming from this comet is in any way different from our native diversity. , “explains Ludmilla Kolokolova, from the University of Maryland in the US, who was involved in research into Nature Communications.
The truth is that we do not know much about the life of comets, especially interstellar ones. But future missions can help paint a complete picture.
Bagnulo hopes astronomers will get another, even better, chance to study a rogue comet in detail before the end of the decade. “ESA plans to launch Comet Interceptor in 2029, which has the ability to reach another attempting interstellar object if one is discovered on a suitable trajectory,” he says, referring to an upcoming mission by European Space Agency.