恒星在与超大质量黑洞的近距离接触中幸存下来，但付出了代价

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

恒星在与超大质量黑洞的近距离接触中幸存下来，但付出了代价

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，看一颗恒星与超大质量黑洞危险相遇的史诗般的故事。这颗星在这次会合中幸存了下来，但付出了可怕的代价。它不再是原来的那颗星星了。

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.

我们故事的背景是星系GSN 069，距离我们所在的宇宙角落2.5亿光年。这个黑洞的质量大约是太阳的40万倍。当然，对于超大质量黑洞来说，它的体积很小，但它仍然是一个强大的引力天体。这颗恒星被认为是一颗红巨星;恒星生命的一个阶段，它的核心耗尽了氢，并开始融合氦，膨胀成一个大而蓬松的物体。

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.

这个特别的红巨星很不幸地遇到了一个超大质量的黑洞。黑洞吸引恒星进入并剥去了它的外层，留下了暴露在外的核心。现在，这颗恒星是一颗白矮星，大约是太阳质量的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.

据《皇家天文学会月报》报道，这颗恒星并没有侥幸逃脱，但它却在许多其他恒星无法逃脱的地方幸存了下来。

"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."

“在我对x射线数据的解释中，白矮星幸存了下来，但它没有逃脱，”莱斯特大学的作者安德鲁·金在一份声明中说。“现在它被困在环绕黑洞的椭圆轨道上，大约每9小时绕黑洞飞行一次。”

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，它在黑洞周围的持续生存并不是免费的。在几乎每天三次接近黑洞的过程中，这颗恒星失去了一些物质。当它被黑洞捕获时，一束x射线被释放出来，正如你在上面看到的。NASA的钱德拉x射线天文台和ESA的xmm -牛顿天文台探测到了这种辐射。

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).

白矮星做出的这种牺牲并不完全是徒劳的。当恒星失去物质时，它变得更轻，它的轨道变宽，使它离黑洞更远。目前，这颗恒星的直径接近900万公里(560万英里)。

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

不过，黑洞和白矮星之间的这种相互作用不会愉快地结束。

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!"

“它会试图逃跑，但没有办法。黑洞会越来越慢地吞噬它，但绝不会停止。”金解释道。“原则上，这种质量的损失将持续到白矮星缩小到木星的质量，大约一万亿年后。这将是一个非常缓慢和复杂的方式，让宇宙形成一颗行星!”

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.

这些观察之所以引人注目，有两个原因。这种相互作用所产生的辐射对我们现在的仪器来说只能观测2000年。所以我们要么非常幸运，要么应该有很多这样的相互作用。另一个值得注意的事实是，我们能够估算2.5亿光年之外的恒星的属性。

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.

这种奇特的相互作用肯定也会释放引力波，未来的太空基地观测站丽莎也许能当场捕捉到它们。