'Oumuamua likely came from binary system

Asteroid ‘Oumuamua is the first known body to enter our Solar System from interstellar space, and probably came from a binary star system, according to new research.

An artist’s impression of ‘Oumuamua.
Credit: ESO / M. Kornmesser


The interstellar asteroid known as ‘Oumuamua probably came from a binary star system, according to astronomers.

A binary star system is one in which two stars are orbiting a common centre.

‘Oumuamua is the first known body to enter our Solar System from interstellar space. It was detected in October 2017 by the Pan-STARRS 1 telescope in Hawaii.


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Dr Alan Jackson of the Centre for Planetary Sciences at the University of Toronto Scarborough in Canada led a team that studied how efficient binary star systems are at ejecting bodies into space.

Their research revealed that rocky objects like ‘Oumuamua are more likely to come from binary systems, rather than single star systems.

The study also found that rocky objects are ejected from binary systems in numbers similar to the ejection of icy bodies.

"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," says Jackson.


An illustration showing ‘Oumuamua’s journey through our Solar System. Approaching from ‘above’, it reached its closest point to the Sun on 9 September 2017, travelling at 44km per second.
Credit: NASA/JPL-Caltech


‘Oumuamua, whose name means ‘scout’ in Hawaiian, has a radius of 200 metres and was spotted travelling 30km per second.

It its closest point to Earth it was about 33,000,000km from our planet.

Initially, astronomers assumed it was a comet, but as it neared the Sun it did not show any comet-like activity and so was classified as a rocky asteroid.

Based on its trajectory and speed, calculations also revealed that it came from outside of our Solar System; the first ever such object to be observed.



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