Solar system's first-known interstellar object likely came from a binary star: Study

Image courtesy: European Southern Observatory/M. Kornmesser

New Delhi: The first-known interstellar cigar-shaped object spotted in October 2017 most likely came from a binary star system, a study has found.

Named ‘Oumuamua' by those who discovered it, the asteroid was highly elongated – up to 400 meters long – perhaps 10 times as long as it is wide.

That aspect ratio is greater than that of any asteroid or comet observed in our solar system to date.

While its elongated structure is quite unusual and surprising, scientists believe that it may provide new clues about how other solar systems formed.

The findings at the time suggested this unusual object had been wandering through the Milky Way, unattached to any star system, for hundreds of millions of years before its chance encounter with our star system.

"It's remarkable that we have now seen for the first time a physical object from outside our solar system," said Alan Jackson from the University of Toronto Scarborough in Canada.

A binary star system, unlike our Sun, is one with two stars orbiting a common center.

For the study, published in the journal Monthly Notices of the Royal Astronomical Society, Jackson and colleagues tested how efficient binary star systems are at ejecting objects.

They also looked at how common these star systems are in our galaxy.

The researchers found that rocky objects like 'Oumuamua are far more likely to come from binary than single star systems.

They were also able to determine that rocky objects are ejected from binary systems in comparable numbers to icy objects.

"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," said Jackson.

Once the researchers determined that binary systems are very efficient at ejecting rocky objects and that a sufficient number of them exist, they were satisfied that 'Oumuamua very likely came from a binary system.

They also concluded that it probably came from a system with a relatively hot, high mass star since such a system would have a greater number of rocky objects closer in.

The team suggests that the asteroid was very likely to have been ejected from its binary system sometime during the formation of planets.

'Oumuamua, which is Hawaiian for 'scout', was first spotted by the Haleakala Observatory in Hawaii in October last year.

With a radius of 200 meters and traveling at a blistering speed of 30 kilometers per second, at its closest, it was about 33,000,000 km from Earth.

When it was first discovered researchers initially assumed the object was a comet, one of the countless icy objects that release gas when they warm up on approaching the Sun.

However, it did not show any comet-like activity as it neared the Sun and was quickly reclassified as an asteroid, meaning it was rocky.

Researchers were also fairly sure it was from outside our solar system, based on its trajectory and speed.

(With PTI inputs)