2010年7月27日星期二

哈勃發現藍星被銀河系'吐出':以160萬哩飛馳穿越時空

哈勃發現藍星被銀河系'吐出':以160萬哩飛馳穿越時空
Hubble spots blue star 'spat out' by Milky Way travelling through space at 1.6million mph

By Daily Mail Reporter
Last updated at 11:48 AM on 23rd July 2010

Nasa's Hubble Space Telescope has detected a rare hypervelocity star that was spat out of the centre of our galaxy and is travelling three times as fast as the Sun.
美國宇航局的哈勃太空望遠鏡,已探測到一顆罕見的超高速恆星,它從我們星系的中心被吐出,及以太陽3倍的速度飛馳。
Scientists believe that it was created when three stars travelling together passed too close to the black hole at the centre of the Milky Way around a hundred million years ago.
科學家相信它是被創造,在約一億年前當三粒星一齊在銀河系中心的黑洞,遊行通過時太接近。
One of the stars was captured while the other two were flung out of the galaxy and merged to form a super-hot blue star travelling at around 1.6 million miles per hour.
一顆星被捕捉而另外兩顆則被扔出星系,和合併形成一顆超熱藍色星,以每小時約 160萬哩遊行。
A Nasa graphic showing how the 'blue straggler' was spat out of the centre of our galaxy
一美國宇航局圖形顯示,'藍色離群者'如何在我們銀河系中心被吐出

Known as HE 0437-5439 it is one of the fastest stars ever detected and is the first to be directly linked with the centre of the galaxy.
被稱為 HE 0437-5439,它是迄今探測到其中一粒速度最快的恆星,及是第一粒直接與星系中心聯繫的。

'Using Hubble, we can for the first time trace back to where the star came from by measuring the star's direction of motion on the sky. Our measurements point directly to the Milky Way center.' said astronomer Warren Brown of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass.

Brown, a member of the Hubble team that observed the star, is the lead author on a paper about the finding published online in the Astrophysical Journal Letters.

Brown said, 'These exiled stars are rare in the Milky Way's population of 100 billion stars. For every 100 million stars in the galaxy, there lurks one hypervelocity star.'

The stellar outcast already is cruising in the Milky Way's distant outskirts about 200,000 light-years from the galaxy's centre.

Using Hubble to measure the runaway star's direction and determine the Milky Way's core as its starting point, Brown and Gnedin's team calculated how fast the star had to have been ejected to reach its current location.

'Studying these stars could provide more clues about the nature of some of the universe's unseen mass, and it could help astronomers better understand how galaxies form,' said team leader Oleg Gnedin of the University of Michigan in Ann Arbor.


The Hubble image which pinpoints the blue star as it hurtles through space at unimaginable speeds
哈勃影象突出藍色的星,當它以難以想像的速度 飛馳穿過空間

The star's age is another mystery. Based on the speed and position of HE 0437-5439, the star would have to be 100 million years old to have journeyed from the Milky Way's core.
But its mass -nine times that of our sun - and blue colour mean that it should have burned out after only 20 million years far shorter than the transit time it took to get to its current location.
This concept for imparting an escape velocity on stars was first proposed in 1988. The theory predicted the Milky Way's black hole should eject a star about once every 100,000 years.
The triple-star system contained a pair of closely orbiting stars and a third outer member also gravitationally tied to the group. The black hole pulled the outer star away from the tight binary system.
The doomed star's momentum was transferred to the other two stars boosting the duo to escape velocity from the galaxy.
http://www.dailymail.co.uk/sciencetech/article-1297075/Hubble-spots-blue-star-spat-Milky-Way-travelling-space-1-6million-mph.html

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