Up to seven alien objects visit our solar system every year, scientists believe

asteroid in deep space lit by a star
'Oumuamua was the first known interstellar object to visit our solar system – but not the last. (Getty)

The cigar-shaped space rock `Oumuamua was the first known interstellar object to visit our solar system, and made headlines around the world as it passed Earth in 2017.

But there could be up to seven such visitors every year, scientists working with the Initiative for Interstellar Studies have said, according to Universe Today.

The calculation is based on data from the Gaia catalogue of nearby stars.

The researchers predict that around 3% of the objects might be even stranger, described as "unbound objects, ejected from our galaxy or entering the Milky Way from another galaxy".

The research is available on the pre-print server ArXiv.

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The second interstellar object spotted in our solar system was 2I/Borisov, spotted by Crimean amateur astronomer Gennadiy Borisov in 2019.

The researchers write: "'Oumuamua and 2I/Borisov, the first interstellar objects (ISOs) discovered passing through the solar system, have opened up entirely new areas of exobody research.

“Finding additional ISOs and planning missions to intercept or rendezvous with these bodies will greatly benefit from knowledge of their likely orbits and arrival rates.

“Here, we use the local velocity distribution of stars from the Gaia Early Data Release 3 Catalogue of Nearby Stars and a standard gravitational focusing model to predict the velocity dependent flux of ISOs entering the solar system.”

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The researchers say that detecting and intercepting such objects could allow us to understand other parts of our galaxy.

Marshall Eubank, a physicist with the Initiative for Interstellar Studies, told Universe Today that the arrival of the two objects created “a field of study almost from nothing (a field that funding authorities are just beginning to recognise).

“Interstellar objects provide us with the opportunity to study, and in the future literally touch, exobodies decades before the earliest possible missions to even the nearest stars, such as Proxima Centauri.

"There are two basic types of missions here – plan and wait, or launch and wait, missions, such as the ESA Comet Interceptor, and chase missions, such as would be needed to reach 1I/'Oumuamua.

"It is very unlikely that any chase missions will be able to rendezvous with a retreating ISO – these will almost certainly be restricted to fast flybys.

"Rendezvous missions, missions to match velocities and orbit or land the ISO, will need advance warning."

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A 2019 paper from Harvard astronomers suggests that another meteor that hit Earth’s atmosphere above Papua New Guinea may also have come from outside our solar system.

Researchers found the meteor – which burnt up in 2014 – by looking for objects that were too fast.

The Papua New Guinea object travelled towards Earth at around 37 miles per second, a speed so high it suggests it originated outside our solar system.

The researchers wrote that the find "implies a possible origin from the deep interior of a planetary system or a star in the thick disk of the Milky Way galaxy".

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