On August 30, 2019, an amateur astronomer named Gennady Borisov observed an object moving in an unusual direction with his home telescope. Dubbed 2I / Borisov, it turned out to be the first confirmed comet to enter our solar system from some unknown location beyond the influence of our Sun.
What is an interstellar comet?
Comets are snowballs of ice, dust and frozen gas, which when heated by the Sun, their tails can extend for millions of kilometers, NASA explains. When they are born in the primordial disk of matter of a young star, they carry the remains of the ancient past of a planetary system, hence an interstellar comet is a carrier of chemical relics from another star system different from ours, with clues about worlds very far away that we are unable to reach with our current technology. Hence its importance.
Borisov’s good news
Now, new observations with ESO’s Very Large Telescope indicate that this wandering comet 2I / Borisov, the second recently detected interstellar visitor in our solar system, is one of the most pristine ever observed. In fact , experts suspect that the comet has most likely never passed near a star – before approaching the Sun in 2019 – so it would be an unaltered relic of the cloud of gas and dust in which it formed. .
Scientists at the European Southern Observatory used the FORS2 instrument to study 2I / Borisov in detail using a technique called polarimetry, which essentially measures the polarization of light (something that happens when light passes through certain filters).
Since this technique is common for studying comets and other small bodies in our solar system, experts were able to compare the interstellar visitor with our local comets.
Not like any kite
According to the data, 2I / Borisov has different polarimetric properties than comets in our solar system, with the exception of Hale-Bopp which, in the late 1990s, was visible to the naked eye, and one of the most common comets. pristines astronomers had ever seen, so
it had hardly been affected by the solar wind and radiation. But, in this case, Borisov is still purer than Hale-Bopp, meaning it contains unaltered traces of the gas and dust cloud in which it originally formed.
“The fact that the two comets are so similar suggests that the environment in which 2I / Borisov originated is not so different in its composition from the environment of the early solar system,” explains Alberto Cellino, co-author of the study and researcher at the Astrophysical Observatory. from Torino, which publishes the journal Nature Astronomy .
When will we know more about him?
The researchers hope to have another opportunity to observe it before the end of the decade.
“ESA plans to launch a Comet Interceptor in 2029, which will have the ability to reach another visiting interstellar object if one is discovered on a suitable trajectory,” the authors clarify.
Comet peculiarities
Astronomers have discovered that the 2I / Borisov coma – an envelope of dust that surrounds the comet’s main body – contains compact pebbles, grains about a millimeter in size or larger. Furthermore, the relative amounts of carbon monoxide and water in the comet changed dramatically as it approached the Sun, indicating that the comet is made up of materials that formed at different places in its planetary system.
2I / Borisov was the first wandering comet to pass the Sun, but not the first interstellar visitor. The first was ʻOumuamua, which was later reclassified as an asteroid, since it does not have a coma.
Referencia: Yang, B., Li, A., Cordiner, M.A. et al. Compact pebbles and the evolution of volatiles in the interstellar comet 2I/Borisov. Nat Astron (2021). https://doi.org/10.1038/s41550-021-01336-w
