study: Interstellar visitors outnumber solar system objects in the Oort cloud | Astronomy



The recent detection of 2I / Borisov, the first known interstellar comet to visit our solar system, implies that interstellar objects outnumber non-interstellar objects in the Oort cloud, while the reverse is true near the Sun in due to the stronger gravitational focus of the limits. objects, according to a new article by astronomers Amir Siraj and Avi Loeb of the Harvard & Smithsonian Center for Astrophysics.

Artist’s impression of what the surface of interstellar comet 2I / Borisov might look like. Image credit: ESO / M. Kormesser.

“Before the detection of the first interstellar comet, we had no idea how many interstellar objects were in our solar system, but the theory about the formation of planetary systems suggests there should be fewer visitors than permanent residents. “said Siraj, first author. paper.

“Now we are seeing that there could be a lot more visitors. “

“The calculations, made on the basis of the conclusions drawn from 2I / Borisov, involve significant uncertainties. “

But even after taking these elements into consideration, interstellar visitors trump objects native to the solar system.

“We just don’t have the technology to see them yet,” Siraj said.

“Consider that the Oort Cloud spans an area between 200 billion and 100,000 billion kilometers from our Sun – and unlike stars, Oort Cloud objects do not produce their own light. “

“These two factors make the debris in the outer solar system incredibly difficult to see.”

“Interstellar objects in the planetary region of the solar system would be rare, but our results clearly show that they are more common than solar system materials in the dark areas of the Oort Cloud,” said Prof Loeb, co- author of the study.

Observations with next-generation technology can help confirm the team’s results.

“The abundance of interstellar objects in the Oort Cloud suggests that there is much more debris left from the formation of planetary systems than previously thought,” Siraj said.

“Our results show that interstellar objects can impose interesting constraints on the formation processes of the planetary system, because their implicit abundance requires the ejection of a large mass of matter in the form of planetesimals.”

“Along with observational studies of protoplanetary disks and computational approaches to the formation of planets, the study of interstellar objects could help us unlock the secrets of the formation of our planetary system – and others.”

The team’s paper was posted online this week in the Monthly notices from the Royal Astronomical Society: letters.


A. Siraj & A. Loeb. 2021. Interstellar objects outnumber solar system objects in the Oort cloud. MNRASL 507 (1): L16-L18; doi: 10.1093 / mnrasl / slab084


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