M87星系-巨型黑洞

伤我心太深

最新研究发现，在我们邻近的M87星系中，存在着一个质量相当于66亿个太阳的巨型黑洞。

科学家认为体积如此巨大的黑洞在宇宙中并不多见，因此在这个相对不算远（五千万光年）的距离内存在这样一个庞然大物实在有些令人诧异。

“从相对位置上来说，这个黑洞大约在我们上方五千万光年左右；事实上这差不多算是我们的后院了。而且这个黑洞如此巨大，这的确有些不寻常。”德克萨斯大学奥斯汀分校的天文学家Karl Gebhardt向探索新闻解释道。

这次的发现修正了之前对于M87星云黑洞大小的估计，现在认为它的大小大约在10到60亿个太阳质量之间。这项研究有助于人们对于更大体积的黑洞进行估计，而这种黑洞可能与名为类星体的古老星系有关。

“这些巨型黑洞的发现非常重要。它们是黑洞的质量最终保留下来的部分。”Gebhardt说。

Gebhardt和他的同事利用坐落于夏威夷的八公尺口径北方双子望远镜上的分光光谱仪测量了围绕M87黑洞运动的星体速度。这个速度理论上与黑洞的引力作用直接相关。获得的数据被用来计算黑洞的质量。

这次获得的结果大约是以前观察的10倍，而Gebhardt 表示其原因主要是由于望远镜精度的提高补偿了地球大气层对光线的扭曲。

天文学家的最终目的是希望能够直接找到质量和能量堕入黑洞的位置，在这个区域中密度变的如此之大以至于连光粒子都无法逃脱其重力作用。这片黑洞的门槛是认知所不能达到之地，也被称作“事件穹界”。

“迄今为止我们还没有证据证明一个星体就是黑洞。但在不久的将来，我们将能够描绘出事件穹界的影子。”Gebhardt说。

同时，科学家也正在用尽一切办法希望了解黑洞与其宿主星系之间的关系，以期获得更多宇宙形成和发展的信息。

最初人们认为，黑洞的尺寸和其宿主星系的大小是成比例的，但这个观点现在看来并不尽然。

“当我们仔细观察的时候，黑洞与星系之间的关系似乎非常复杂。”来自佛罗里达理工学院的天文学家，M87星系研究专家Dan Batcheldo说，“在接下去几年的研究中，我们将会寻找越来越多的非典型黑洞。”

Gebhardt的研究成果将在周三于西雅图举行的美国天文会议上展示，同时将在下期天文物理学期刊上发表

【Discovery News】Obese Black Hole Lurks in Our BackyardThe black hole inside a neighboring galaxy, known as M87, is obese and filled with the equivalent of 6.6 billion of our suns, according to new measurements.
These supermassive black holes are relatively rare, scientists suspect, so it is surprising that such a behemoth lives relatively close by -- just 50 million light-years away.
"It's almost on top of us, relatively speaking. Fifty million light-years -- that's our backyard effectively. To have one so large, that's kind of extreme," astronomer Karl Gebhardt, with the University of Texas at Austin, told Discovery News.
The finding refines previous estimates of the size of M87's black hole, which ranged from one billion to more than six billion times the mass of the sun. The research is expected to help nail down estimates of even bigger black holes associated with ancient distant galaxies known as quasars.
"It's important to find these very large black holes. It's the upper end of the black hole mass that really matters," Gebhardt said.
Gebhardt and colleagues used a light-splitting spectrograph on the eight-meter (26-foot) Gemini North telescope in Hawaii to measure the speeds of stars orbiting M87's black hole. The motions are directly related to the gravitational pull of the black hole. The data was then used to calculate the black hole's mass.
The measurements are about 10 times better than previous observations, largely because of telescope enhancements that compensate for distortions in Earth's atmosphere, Gebhardt added.
Eventually, astronomers hope to be able to directly detect the point where matter and energy fall into a black hole, a region of space so densely packed that not even photons of light can escape its gravitational grasp. The doorstep to the black hole, from which there is no known exit, is known as the event horizon.
"Right now we have no evidence that an object is a black hole. Within a few years, we might be able to image the shadow of the event horizon," Gebhardt said.
Scientists have been wrestling to understand the relationship between black holes and host galaxies in hopes of learning more about how the universe came to exist and evolve.
Initial observations that the size of a black hole and the size of its host galaxy were matched are turning out to not always be the case.
"The relationship appears to be more complicated the closer we look," astronomer and M-87 researcher Dan Batcheldor, with the Florida Institute of Technology, told Discovery News. "In the next couple of years, we're going to start seeing more and more black holes that are atypical."
Gebhardt's research was presented on Wednesday at the American Astronomical Society meeting in Seattle and will be published in an upcoming issue of The Astrophysical Journal.