The 2I / Borisov star visitor is the cleanest comet ever studied by humans
We studied enough comets in our solar system to find that they were formed in their early stages, when a pile of material spun and came together in a single body. They are mostly made of ice, but in order to survive, they must be created at a distance where the sun’s heat and radiation will not melt immediately. Other star systems are thought to create comets in the same way. The farther away they are from the star’s radiation, the earlier they retain their original composition and chemistry 4.5 billion years or so ago. This “pristine” quality means that comets are preserved in time capsules of stellar systems in childhood.
Comet dust, in particular, tells us what the solar system was made of when it created comets, and the same principle can theoretically be applied to inter-star comets. “By studying the composition and structure of dust particles in the 2I / Borisov dust coma, we can make guesses about the conditions and locations of dust formation,” says bin Yang, an astronomer and researcher at the Southern European Observatory.
The first article, directed by Stefano Bagnulo at the Armagh Observatory and Planetarium in the UK, focuses on light. Light is made up of waves, and these waves usually oscillate in several directions at the same time. When these waves are polarized, however, they oscillate in a specific direction. If the light is polarized by the comet’s comet (a fuzzy outer shell of gas and dust expelled when the sun heats it), examining that light can provide information about the size and composition of the dust, which will help us understand how the comet is. was formed and, by extension, gives a look at the history of its original star system.
New data from the Very Large Telescope in Chile tells us that light reflected from Borisov and filtered through a coma is more polarized than light from any other object we have studied in the solar system. A comma is a sign that the particles are small and very fine. This suggests that the star’s radiation and heat did not disturb them much (otherwise, the forces that would cause larger parts to be expelled from the surface). The authors conclude that Borisov is one of the cleanest objects ever detected. The only object approaching polarization is C / Hale-Bopp, the brightest comet ever seen, and certainly the twentieth. One of the most studied comets of the century. Hale-Bopp is thought to have approached the sun before its last solar flight in 1997. So the authors believe that similar conditions can give rise to Borisov and Hale-Bopp in two different star systems.
Meanwhile, the team led by Yang intended to understand how Borisov was formed by using the VLT and the Chilean Atacama Large Millimeter / Submillimeter Array (ALMA) to detect the heat of large particles hanging from the Borisov coma.
According to these observations, Borisov’s coma is made up of millimeter-sized dense grains, pebbles that are unusually large for comets. These rocks, rich in carbon monoxide and water, were probably formed in the inner region of the star system before being transported outside and mixed with various ice sheets formed in different places far from the star. This “gravitational turbulence” caused by giant planets is thought to have occurred in the solar system (Hale-Bopp is believed to have helped make it up). Borisov essentially gathered as an agglomeration of materials from different parts of his star system before finding a solitary place to call home away from his main star.
Taken together, the findings help us tell a few things. Because carbon monoxide and water are abundant in dust, the comet lives in low-temperature environments (far from a star) where these compounds could remain cold and stable for most of its life. Finding “clean” features reinforces this idea.
The similarities between Borisov and Hale-Bopp, along with proving that the stellar systems of the two comets suffered from gravitational turbulence, are as unique as we might think the evolution of our solar system might be. This could also suggest that the conditions that create a habitable planet like Earth are more common in the galaxy than imagined.
Or maybe it’s the red herring, and Borisov’s home star system is truly exotic. Neil Dello Russo, an astronomer at Johns Hopkins University and a non-participant in the study, was surprised to learn how much carbon monoxide and water values were — higher than anything seen in comets in our solar system.
Other questions also remain. New discoveries still can’t tell us exactly when the coma pebbles were created, or what they look like.
The most serious problem may be that the two papers promote two different ideas about the particles that make up Borisov: Yang’s paper dismantles the discovery of large pebble stones, Bagnulo’s paper suggests that small specimens like coma smoke predominate. can cause extreme polarization of light. But Michael Kelley, a comet scientist at the University of Maryland who was not involved in the new research, believes it is “just the result of different techniques” – each advocating the detection of a specific type of particle. Future analyzes should be able to compare and combine the two data sets and combine them as part of Borisov’s evolution.
Borisov is a strange object, but what is really strange is the idea that it can arise from a star system unlike ours. This inter-star comet may be one of the most normal visitors we have ever greeted.