天文学家首次清晰观测到银河系中心黑洞

http://www.sciam.com.cn/article.php?articleid=2363
http://www.astronomy.com/asy/default.aspx?c=a&id=7351





北京时间9月5日消息，据物理学家组织网4日报道，天文学家对银河系中心的巨大黑洞进行了有史以来一个“最亲密接触”。在位于夏威夷、亚利桑那州和加利福尼亚州的3架望远镜通力合作下，他们对黑洞附近区域进行了解析度高达37微角秒的观测，相当于在24万英里(约合38公里)远的地方观察到月球表面上的一个棒球。据悉，此次观测结果的解析度在天文学历史上是最高的。

                               
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银河系中心黑洞

观测报告主执笔人、麻省理工学院的谢弗德·杜勒曼(Sheperd Doeleman)表示：“这项技术让我们有机会对银河系中心的黑洞附近区域进行前所未有的观测。”联合执笔人、哈佛-史密松森天体物理学中心的乔纳森·韦恩特劳伯(Jonathan Weintroub)说：“在此之前，没有人对银河系中心进行过如此细致的观察。我们对黑洞的事件穹界(黑洞边界)进行了观测，任何事物都无法从这一区域逃脱，包括光线在内。”观测报告将刊登在9月4日出版的《自然》杂志上。

利用一种被称之为“甚长基线干涉测量”(以下简称VLBI)的技术，由杜勒曼挂帅的天文学家小组使用一个望远镜阵列对来自人马座A星的无线电波进行了研究。VLBI能够将来自多个望远镜的信号进行合并，相当于使用一架巨型望远镜，从而得到极高的解析度。

人马座A星发射的无线电波长为1.3毫米，相对于更大波长的无线电来说，它们能够更容易地逃离银河系中心。更长的波长往往受到星际散射影响。此时的散射就像是街灯周围的烟雾，在降低亮度的同时让细节变得模糊。VLBI通常只能对3.5毫米以上的波长进行观测，但通过创新性的仪器使用和分析技术，天文学家小组可以得到1.3毫米波长条件下的数据。

观测过程中，天文学家小组清楚地观察到银河系中心的结构，解析度高达37微角秒，相当于3000万英里(约合4828公里)或者地日距离的大约三分之一。在3架望远镜帮助下，天文学家只能含糊地确定这个放射区的形状。未来的研究将帮助给出有关他们正在观察的黑洞周围一个光环(一个绕轨道运行的“热点”或者说一个喷射物质的区域)更为准确的答案。不管怎样，此次观测都是有史以来与黑洞的第一次“最亲密接触”，它的施瓦兹希尔德半径达到1000万英里(约合1609公里)。

哈佛大学理论家亚韦·洛布(Avi Loeb)评价说：“这是一份具有开创性的观测报告，说明如此高解析度的观测是可以做到的，同时也打开了探测黑洞附近时空结构的一扇新窗口并验证爱因斯坦的重力理论。”洛布并没有参与此次观测。

2006年，洛布和同事艾弗里·罗德里克(Avery Broderick)研究了，如何利用对银河系中心进行超高清晰成象寻找“潜伏”在那里的超大质量黑洞的阴影或者轮廓，以及内部包含被吸入黑洞的物质的“热区”。现在，天文学家正计划对这些在理论上做出的假设加以验证。韦恩特劳伯说：“这是一次极不寻常的观测，观测结果证实1.3毫米波长下的VLBI技术具有巨大的潜在用途，可以用于探测银河系中心，同时也可研究类似条件下的其它现象。”(孝文）









以下是美国著名的天文学杂志《Astronomy〉〉的报道：



To the edge of a black hole


                    Astronomers have taken the closest look ever at the giant black hole in the center of the Milky Way.
    Provided by the Harvard-Smithsonian CfA

                    

登录/注册后可看大图 Thisclose-up view here represents the immediate vicinity of the black hole,with the event horizon depicted as a black sphere. The surrounding diskof gas, represented by white and blue rings, whirls around the blackhole. The white column over the pole of the black hole represents a jetof gas being ejected from the vicinity of the black hole at nearly thespeed of light. NASA

Bycombining telescopes in Hawaii, Arizona, and California, astronomersdetected structure at a tiny angular scale of 37 micro-arcseconds — theequivalent of a baseball seen on the surface of the Moon, 240,000 milesdistant — on the edge of a black hole. These observations are among thehighest resolution ever done in astronomy.

"This technique givesus an unmatched view of the region near the Milky Way's central blackhole," says Sheperd Doeleman of MIT, first author of the study thatwill be published in the September 4 issue of the Nature.

"Noone has seen such a fine-grained view of the galactic center before,"agrees coauthor Jonathan Weintroub of the Harvard-Smithsonian Centerfor Astrophysics (CfA). "We've observed nearly to the scale of theblack hole event horizon — the region inside of which nothing,including light, can ever escape."

Using a technique called VeryLong Baseline Interferometry (VLBI), a team of astronomers led byDoeleman employed an array of telescopes to study radio waves comingfrom the object known as Sagittarius A*. In VLBI, signals from multipletelescopes are combined to create the equivalent of a single gianttelescope, as large as the separation between the facilities. As aresult, VLBI yields exquisitely sharp resolution.

The Sgr A*radio emission, at a wavelength of 1.3 millimeters, escapes thegalactic center more easily than emissions at longer wavelengths, whichtend to suffer from interstellar scattering. Such scattering acts likefog around a streetlamp, both dimming the light and blurring details.VLBI is ordinarily limited to wavelengths of 3.5 millimeters andlonger; however, using innovative instrumentation and analysistechniques, the team was able to tease out this remarkable result from1.3-millimeters VLBI data.

The team clearly discerned structurewith a 37 micro-arcsecond angular scale, which corresponds to a size ofabout 30 million miles (or about one-third the Earth-Sun distance) atthe galactic center. With three telescopes, the astronomers could onlyvaguely determine the shape of the emitting region. Futureinvestigations will help answer the question of what, precisely, theyare seeing: a glowing corona around the black hole, an orbiting "hotspot," or a jet of material. Nevertheless, their result represents thefirst time that observations have gotten down to the scale of the blackhole itself, which has a "Schwarzschild radius" of 10 million miles.

"Thispioneering paper demonstrates that such observations are feasible,"comments theorist Avi Loeb of Harvard University and frequentcontributor to Astronomy, who is not a member of the discoveryteam. "It also opens up a new window for probing the structure of spaceand time near a black hole and testing Einstein's theory of gravity."

In2006, Loeb and his colleague, Avery Broderick, examined howultra-high-resolution imaging of the galactic center could be used tolook for the shadow or silhouette of the supermassive black holelurking there, as well as any "hot spots" within material flowing intothe black hole. Astronomers now are poised to test those theoreticalpredictions.

"This result, which is remarkable in and of itself,also confirms that the 1.3-mm VLBI technique has enormous potential,both for probing the galactic center and for studying other phenomenaat similar small scales," says CfA's Weintroub.

The team plansto develop novel instrumentation to make more sensitive 1.3-mmobservations possible. It also hopes to develop additional observingstations, to gain extra baselines (pairings of two telescope facilitiesat different locations) to enhance the detail in the picture. Futureplans also include observations at shorter, 0.85-mm wavelengths;however, such work will be even more challenging for many reasons,including stretching the capabilities of the instrumentation, and therequirement for a coincidence of excellent weather conditions at allsites.

老师上课说谁观测到nobel就是谁的……看能不能得上。

就是那个建在智利的Very Large 什么的，四台巨镜同时使用，然后信号进入干涉仪的玩意吗？？

果然现阶段nobel不可能产生在中国产生，客观现实

原文：在位于夏威夷、亚利桑那州和加利福尼亚州的3架望远镜通力合作下，

没有提到建在智利的 VLT。