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Alien Visitor 'Oumuamua Most Likely Ejected By A Two-Star System: How Did That Happen?

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'Oumuamua, the cigar-shaped interstellar asteroid that astronomers first spotted zooming through the Solar System in October, was likely ejected from a binary star system.

Ejected By A Binary Star System

In a new study, Alan Jackson, of University of Toronto at Scarborough, Canada, and colleagues found that 'Oumuamua probably did not come from a system like our own.

Using computer modeling, the researchers found that rocky objects such as our first interstellar visitor are more likely to originate from a binary rather than a single star system. Unlike the solar system, which has only one sun, a binary star system has two stars orbiting a common center.

Jackson and his team found that systems with two close-orbiting stars are more efficient at booting out asteroids compared with one-star systems.

Single star systems are better at ejecting icy comets than asteroids because comets lie much further from the solar system's sun, which makes them more weakly bound by gravity than the nearer asteroids.

Two-star systems have stronger gravitational fields because there are two, not just one, stars orbiting each other. This makes binary star systems capable of booting out as many asteroids as comets into interstellar space.

"It's really odd that the first object we would see from outside our system would be an asteroid, because a comet would be a lot easier to spot and the Solar System ejects many more comets than asteroids," Jackson said.

How Asteroids And Comets Get Ejected Out Of Their Home Star System

'Oumuamua was highly likely born into a two-star system that harbors at least one big hot star. Researchers explained that this type of star system is more likely to have predominantly rocky bodies instead of icy bodies that orbit relatively close to the prime ejection zone.

Jackson and colleagues also said that the rock was likely ejected out of its home star system during the planet formation period.

NASA earlier explained how asteroids and comets stray into interstellar space. A large percentage of the original planetesimals that were around in the early solar system was ejected into interstellar space through encounters with Jupiter. Many of the original asteroids and comets were dispersed by the young Jupiter, which either spewed them out into interstellar space or into the sun.

NASA said that planetary systems that formed around other stars possibly evolved in the same manner with Jupiter-sized planets also ejecting the star system's own asteroids and comets into interstellar space.

"Galactic budget of interstellar objects like 1I/'Oumuamua should be dominated by planetesimal material ejected during planet formation in circumbinary systems, rather than in single star systems or widely separated binaries," the researchers wrote in their study, which was published in the journal Monthly Notices of the Royal Astronomical Society.

"The rocky population, of which 1I/'Oumuamua seems to be a member, should be predominantly sourced from A-type and late B-star binaries."

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