“Our” Oort cloud may have more interstellar visitors than native objects

Interstellar comets like 2I / Borisov may not be as rare as we think.

In 2019, something incredible happened in our cosmic backyard. Astronomers have discovered that an interstellar comet had invaded our solar system. The ice ball, named 2I / Borisov, rushed at an incredible speed of 177,000 miles per hour. It was the first and so far the only comet from another galaxy that we have seen. But what if such interstellar visitors visit us more often than we think?

Covered
In a new study, researchers come up with a bold hypothesis. They present new calculations showing that the Oort Cloud – a supposed cloud of several billion comet-like objects surrounding the solar system – harbors more interstellar visitors than native objects belonging to our own solar system. The calculations, carried out on the basis of the conclusions concerning 2I / Borisov, contain considerable uncertainties, underlines researcher Amir Siraj. “But even after taking these things into account, interstellar visitors take precedence over native objects.”

Learn more about the Oort cloud
The existence of the Oort cloud was suggested in 1950 by the Dutch astronomer Jan Hendrik Oort. This cloud would explain the ever new comets with elongated orbits in our solar system. The disturbances of comets in this cloud – for example, stars passing through our solar system – would drag the wedge of some of them out of the Oort cloud, landing in an elliptical orbit around the sun, passing inside our solar system.

It’s a remarkable theory. Because until now, the exact opposite has been assumed. “Before the detection of the first interstellar comet, we had no idea how many interstellar objects were in our solar system,” says Siraj. “But the theory of the formation of planetary systems suggests that there should be fewer visitors than permanent residents. Now we notice that there could be a lot more visitors.

An example
How did the researchers come up with this idea? “Let’s say I spend a day looking at a mile-long railroad track and see a car crossing the road,” says Siraj. “So I can say that the number of cars that crossed the tracks that day is one per day per kilometer. But if I have reason to believe that this sighting was not a one-off event – for example because of the placement of barriers – then I can go further and draw static conclusions about the number of cars crossing the road. track in question. “

Question
A pressing question then, however, is; if there are so many interstellar comets, why have we only seen one so far? “We don’t yet have the technology to detect them,” says Siraj. “Remember that the Oort cloud extends over an area between 300 and 160,000 billion kilometers from the sun. And unlike stars, objects in the Oort Cloud do not produce their own light. These two factors make the debris in the far reaches of our solar system incredibly difficult to observe. “

Planets
The theory could have implications for how we see asteroids. “Looking at the data on the asteroids, one wonders if some may be interstellar but not yet recognized as such,” said astrophysicist Matthew Holman, not involved in the study. Holman explains that after the discovery of an asteroid, it is neither observed nor studied every year. “We think they are asteroids, but then we lose track of them without really looking at them,” he says.

Vera C. Rubin-observatory
Observations with future improved technology could help confirm the research team’s findings. They are eagerly awaiting the launch of the Vera C. Rubin Observatory, which will take off in 2022. This telescope will scan, among other things, the outer regions of our solar system, looking for interesting objects. Rubin is expected to discover about ten times more asteroids than those currently known. “We hope to detect a lot more interstellar visitors like 2I / Borisov,” Siraj said.

If there is indeed an abundance of interstellar objects in the Oort Cloud, that would also mean that there is much more debris left from the formation of planetary systems than previously thought. “With observational studies of protoplanetary disks and computerized approaches to the formation of planets, the study of interstellar objects could help us unlock the secrets of the formation of our planetary systems – and others -“, concludes Siraj.