Mystery of hypervelocity star unveiled

02 October, 2009, 21:07

A Russian astronomer from Moscow State University has explained the origin of the hypervelocity runaway star HD 271791 and the nature of its extremely high velocity.

The Russian researcher, Vasily Gvaramadze from the Sternberg Institute of Moscow State University, published his report in the Proceedings of the symposium of the International Astronomical Union.

Hypervelocity stars (HVS) are characterized with an extremely high speed relative to the Galactic Center of our galaxy – the Milky Way. It exceeds a stunning 1000 kilometers per second. Such a velocity is high enough for a space object to be able to leave the galaxy.

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The existence of HVS was predicted by astronomers some 20 years ago, who showed that a close encounter between a tight binary system and the supermassive black hole in the Galactic Centre could be responsible for the ejection of one of the binary components with a velocity of up to several thousand kilometers per second, while the second component gets absorbed by the black hole.

HD 271791 is among the best studied HVS known to date. It is 11 times as heavy as the Sun, and previous research has shown that this star has never had a close encounter with the supermassive black hole in the Galactic Centre of the Milky Way. On the contrary, it takes its origin from the “outskirts” as far as 3000 light years away.

The major achievement of Gvaramadze’s research is that he managed to explain the way the star has gained such an astonishing velocity.

In his opinion, its speed is due to the gravitational interference of several stars. In this scenario, HD 271791 could have attained its peculiar velocity in the course of a strong interaction between two hard massive binaries.

Alternatively, an exchange encounter between a hard massive binary and a very massive star, around 300 times as heavy as the Sun, could be the reason.

Further observations of the star are expected to disclose which of the two scenarios actually took place.

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