恒星在與超大質(zhì)量黑洞的近距離接觸中幸存下來，但付出了代價

Star Survives Close Encounter With A Supermassive Black Hole, But At A Price

恒星在與超大質(zhì)量黑洞的近距離接觸中幸存下來，但付出了代價

Gather round for the epic tale of a star’s dangerous encounter with a supermassive black hole. The star survived this rendezvous, but at a terrible price. It was no longer the same star it once was.

聚集在一起，看一顆恒星與超大質(zhì)量黑洞危險相遇的史詩般的故事。這顆星在這次會合中幸存了下來，但付出了可怕的代價。它不再是原來的那顆星星了。

The setting of our story is galaxy GSN 069, located 250 million light-years from our corner of the universe. The black hole in question has a mass of about 400,000 times that of our Sun. Certainly on the small size when it comes to supermassive black holes, but nevertheless a powerful gravitational object. The star is believed to have been a red giant; the phase in a star’s life where it has run out of hydrogen at its core and has begun fusing helium, swelling into a large and puffy object.

我們故事的背景是星系GSN 069，距離我們所在的宇宙角落2.5億光年。這個黑洞的質(zhì)量大約是太陽的40萬倍。當(dāng)然，對于超大質(zhì)量黑洞來說，它的體積很小，但它仍然是一個強(qiáng)大的引力天體。這顆恒星被認(rèn)為是一顆紅巨星;恒星生命的一個階段，它的核心耗盡了氫，并開始融合氦，膨脹成一個大而蓬松的物體。

This particular red giant had the misfortune to meet a supermassive black hole. The black hole lured the star in and stripped it of its outer layers, leaving its exposed core behind. Now, the star is a white dwarf about 20 percent of the mass of the Sun.

這個特別的紅巨星很不幸地遇到了一個超大質(zhì)量的黑洞。黑洞吸引恒星進(jìn)入并剝?nèi)チ怂耐鈱?，留下了暴露在外的核心。現(xiàn)在，這顆恒星是一顆白矮星，大約是太陽質(zhì)量的20%。

As reported in the Monthly Notices Of The Royal Astronomical Society, the star didn't quite make a lucky escape, but it did survive where many others haven't.

據(jù)《皇家天文學(xué)會月報》報道，這顆恒星并沒有僥幸逃脫，但它卻在許多其他恒星無法逃脫的地方幸存了下來。

"In my interpretation of the X-ray data the white dwarf survived, but it did not escape," author Andrew King of the University of Leicester, said in a statement. "It is now caught in an elliptical orbit around the black hole, making one trip around about once every nine hours."

“在我對x射線數(shù)據(jù)的解釋中，白矮星幸存了下來，但它沒有逃脫，”萊斯特大學(xué)的作者安德魯·金在一份聲明中說。“現(xiàn)在它被困在環(huán)繞黑洞的橢圓軌道上，大約每9小時繞黑洞飛行一次。”

The x-ray signals seen every 9 hours over the artist's impression. X-ray: NASA/CXO/CSIC-INTA/G.Miniutti et al.; Illustration: NASA/CXC/M. Weiss;

Its continuous survival around the black hole does not come for free, though. During its nearly thrice-daily approach to the black hole, the star loses a bit of material. As this is captured by the black hole, a burst of X-rays is released, as you can see above. This emission was detected by NASA's Chandra X-ray Observatory and ESA's XMM-Newton observatories.

然而，它在黑洞周圍的持續(xù)生存并不是免費(fèi)的。在幾乎每天三次接近黑洞的過程中，這顆恒星失去了一些物質(zhì)。當(dāng)它被黑洞捕獲時，一束x射線被釋放出來，正如你在上面看到的。NASA的錢德拉x射線天文臺和ESA的xmm -牛頓天文臺探測到了這種輻射。

This sacrifice the white dwarf makes is not completely in vain. As the star loses material, it becomes lighter and its orbit grows wider, taking it further from the black hole. Currently, the star gets as close as 9 million kilometers (5.6 million miles).

白矮星做出的這種犧牲并不完全是徒勞的。當(dāng)恒星失去物質(zhì)時，它變得更輕，它的軌道變寬，使它離黑洞更遠(yuǎn)。目前，這顆恒星的直徑接近900萬公里(560萬英里)。

This interaction between the black hole and the white dwarf will not end happily, though.

不過，黑洞和白矮星之間的這種相互作用不會愉快地結(jié)束。

A schematic diagram showing an almost complete orbit of the white dwarf around the black hole at the center of the figure. NASA/CXC/M. Weiss;

"It will try hard to get away, but there is no escape. The black hole will eat it more and more slowly, but never stop," explained King. "In principle, this loss of mass would continue until and even after the white dwarf dwindled down to the mass of Jupiter, in about a trillion years. This would be a remarkably slow and convoluted way for the universe to make a planet!"

“它會試圖逃跑，但沒有辦法。黑洞會越來越慢地吞噬它，但絕不會停止。”金解釋道。“原則上，這種質(zhì)量的損失將持續(xù)到白矮星縮小到木星的質(zhì)量，大約一萬億年后。這將是一個非常緩慢和復(fù)雜的方式，讓宇宙形成一顆行星!”

These observations are remarkable for two reasons. The emission that this interaction produces would be visible to our current instruments for just 2,000 years. So we are either incredibly lucky or there should be a lot of these interactions out there. The other remarkable fact is the ability to estimate the properties of a star 250 million light-years away.

這些觀察之所以引人注目，有兩個原因。這種相互作用所產(chǎn)生的輻射對我們現(xiàn)在的儀器來說只能觀測2000年。所以我們要么非常幸運(yùn)，要么應(yīng)該有很多這樣的相互作用。另一個值得注意的事實(shí)是，我們能夠估算2.5億光年之外的恒星的屬性。

The peculiar interaction will also certainly release gravitational waves and the future space-base observatory LISA might be able to catch them in the act.

這種奇特的相互作用肯定也會釋放引力波，未來的太空基地觀測站麗莎也許能當(dāng)場捕捉到它們。