Interstellar objects do not often visit the Solar System, but there are a notable few. The first one was Oumuamua, which means scout or messenger in Hawaiian, seen in 2017; while the second one was comet 2I/Borisov, the first rogue comet and the second interstellar object.

However, a recently published study claims that perhaps the Solar System is visited by interstellar objects more often than scientists previously thought.

 Solar System May Be Full of Interstellar Objects than Previously Thought
(Photo: Wikimedia Commons)
NASA's Hubble Space Telescope has given astronomers their best look yet at an interstellar visitor – comet 2I/Borisov – whose speed and trajectory indicate it has come from beyond our solar system.

Interstellar Visitors Outnumber Solar System Objects in Oort Cloud

Amir Siraj, the lead author of the study, said that before discovering the first interstellar comet, scientists have no clue how many interstellar objects exist in the Solar System. The theory of the formation of the Solar System proposes that there are more Solar System objects than interstellar visitors.

However, the opposite is true as experts have calculated that interstellar objects outnumber Solar System objects. According to Forbes, this is only true for those objects in the Oort Cloud.

NASA said that Oort Cloud is the most distant region of the Solar System, farther than the Kuiper Belt. The Oort Cloud is thought to be a large spherical shell surrounding the planetary system, like a big walled bubble made of icy space debris the size of mountains. Also, it is believed to contain billions or perhaps trillions of objects.

Forbes further reported that the study titled "Interstellar Objects Outnumber Solar System Objects in the Oort Cloud," published in the Monthly Notices of the Royal Astronomical Society, suggests that native comets in the Oort cloud might be outnumbered 10 to 1 by interstellar comets.

However, these interstellar comets are not readily visible to humans from Earth. One reason could be that the comets that can only be seen are those near the Earth or within its vicinity.

Another reason could also be the lack of technology to see the objects in the Oort cloud. However, with future improvements and space programs, scientists hope to see close to this distant region of the Solar System.

"These results suggest that the abundances of interstellar and Oort cloud objects are comparable closer to the Sun than Saturn," Forbes quoted astrophysicist Matthew Holman.

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Study of Interstellar Objects Could Give Insights on Formation of Solar System

Now that scientists have found two interstellar objects, their hunch that the Solar System might be swarming with interstellar objects is confirmed. However, according to BBC Future, predicting how often they appear visible from Earth is extremely tricky.

Before Oumuamua and Borisov were detected, an early calculation in 2009 estimated the density of stars in the Milky Way. This include assumptions that the matter that each star ejects are comparable to the sensitivity of the telescopes available. This calculation says that scientists should not have seen the Oumuamua, but they did.

Siraj said that studying interstellar objects could help scientists unlock the secrets of the formation of the Solar System. If the Oort Cloud indeed is dominated by interstellar objects, there must be more debris left from the time the Solar System formed.

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