Interstellar comets like 2I/Borisov may not be as rare as we think.
In 2019, something incredible happened in our cosmic backyard. Astronomers discovered that An interstellar comet invaded our solar system. The ice sphere – called 2I/Borisov – rushed at an amazing speed of 177,000 miles per hour. It was the first and so far only comet from another galaxy we’ve seen. But what if these interstellar visitors visit us more often than we think?
In a new study, researchers come up with a bold hypothesis. They present new calculations showing that the Oort Cloud – a hypothesized cloud of several billion comet-like objects surrounding the Solar System – harbors more interstellar visitors than the original objects from our Solar System. Researcher Amir Siraj asserts that the calculations, made on the basis of conclusions about 2I / Borisov, contain a great deal of uncertainty. “But even after thinking about these things, interstellar visitors take precedence over the original stuff.”
More about the Oort cloud
The existence of the Oort cloud was proposed by Dutch astronomer Jan Hendrik Oort in the year 1950. This cloud explains the constantly new comets with long orbits in our solar system. Turbulence from comets in this cloud—for example, from stars passing through our Solar System—may cause some of them to isolate from the Oort Cloud, and to land in an elliptical orbit around the Sun, passing through the interior of our Solar System.
It’s a wonderful theory. Because so far, the exact opposite has been assumed. “Before the discovery of the first interstellar comet, we had no idea how many interstellar objects there were in our solar system,” says Siraj. But the theory about the formation of planetary systems suggests that there should be fewer visitors than permanent residents. Now we notice that there may be much more visitors.”
How did the researchers come to this idea? “Suppose I spent a day looking at a mile-long railroad track and saw one car crossing the road,” explains Siraj. I can then say that the number of cars that crossed the railway on that day is one car per day per kilometer. But if I had reason to believe that this vision was not a one-time event – say because of the barriers put in place – then I can go a step further and draw firm conclusions about the number of cars crossing the path in question. “
The urgent question then is; If there are so many interstellar comets, why have we seen only one so far? “We don’t have the technology to detect it yet,” says Siraj. “Remember that the Oort Cloud extends over an area of about 300 billion to 160 trillion km from the Sun. Unlike stars, objects in the Oort Cloud do not produce their own light. These two factors make debris in the outer reaches of our solar system extremely difficult to observe.”
This theory could have implications for the way we view asteroids. “Looking at the data for asteroids, we might wonder if some of them exist among the stars but aren’t yet identified as such,” said astrophysicist Matthew Holman, who was not involved in the study. Holman explains that after an asteroid is discovered, it is not observed or studied annually. “We think they are asteroids, but then we lose track of them without taking a close look at them,” he says.
Vera Sea Rubin Observatory
Observations with improved technology in the future could help confirm the research team’s findings. They are eagerly looking forward to the launch of the Vera C. Rubin Observatory, which will soar into the sky in 2022. This telescope will, among other things, survey the outer regions of our solar system, looking for interesting things. Robin is expected to discover about ten times the number of asteroids currently known. “We hope to reveal more interstellar visitors like 2I/Borisov,” said Siraj.
If there are indeed an abundance of interstellar objects in the Oort cloud, this also means that there is more debris left from the formation of planetary systems than previously thought. “Together with observational studies of protoplanetary disks and computational approaches to planet formation, studying interstellar bodies can help us unlock the secrets of how our planetary systems—and others—formed,” concludes Siraj.
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