银河系发现新式巨大的星体结构
文章来源:未知 文章作者:meng 发布时间:2010-11-10 03:15 字体: [ ]  进入论坛
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NASA's Fermi Gamma-ray Space Telescope has unveiled a previously1 unseen structure centered in the Milky2 Way -- a finding likened in terms of scale to the discovery of a new continent on Earth. The feature, which spans 50,000 light-years, may be the remnant(剩余) of an eruption3 from a supersized black hole at the center of our galaxy4. "What we see are two gamma-ray-emitting bubbles that extend 25,000 light-years north and south of the galactic center," said Doug Finkbeiner, an astronomer5 at the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass., who first recognized the feature. "We don't fully6 understand their nature or origin."

At more than 100 degrees across, the structure spans more than half of the sky, from the constellation7(星座,星群) Virgo to the constellation Grus. It may be millions of years old.

A paper on the findings will appear in an upcoming issue of The Astrophysical(天体物理学的) Journal.

Finkbeiner and Harvard graduate students Meng Su and Tracy Slatyer revealed the bubbles by processing publicly available data from the satellite's Large Area Telescope (LAT). Their work expanded on previous studies led by Greg Dobler at the Kavli Institute for Theoretical Physics in Santa Barbara, Calif.

Fermi's Large Area Telescope is the most sensitive and highest-resolution gamma-ray detector8 ever orbited. Gamma rays are the highest-energy form of light.

The structures eluded9(逃避,躲避) previous astronomers10 studying gamma rays due in part to the so-called diffuse11(弥漫的,散开的) emission12 -- a fog of gamma rays that appears all over the sky. The emissions13 are caused by particles moving near the speed of light interacting with light and interstellar gas(星际气体) in the Milky Way.

The Fermi LAT team is constantly refining models to uncover new gamma-ray sources obscured by the diffuse emission. By using various estimates of the gamma-ray fog, including the Fermi team's, Finkbeiner and his colleagues were able to subtract it from the LAT data and unveil the giant bubbles.

"The LAT team confirmed the existence of an extended structure in the direction of the inner part of the Milky Way and we're in the process of performing a deeper analysis to better understand it," said Simona Murgia, a Fermi research associate at the SLAC National Accelerator Laboratory in Menlo Park, Calif.

The researchers believe that an important process for producing the Milky Way's gamma-ray fog, called inverse14(相反的,倒转的) Compton scattering15, also lights up the bubbles. In that process, electrons moving near the speed of light collide with low-energy light, such as radio or infrared16 photons. The collision increases the energy of the photons into the gamma-ray part of the electromagnetic spectrum17.

The bubble emissions are much more energetic than the gamma-ray fog seen elsewhere in the Milky Way.

The bubbles also appear to have well-defined edges. Taken together, the structure's shape and emissions suggest that it was formed as a result of a large and relatively18 rapid energy release -- the source of which remains19 a mystery, Finkbeiner noted20.

One possibility includes a particle jet from the supermassive black hole at the galactic center. In many other galaxies21, astronomers see fast particle jets powered by matter falling toward a central black hole. While there is no evidence that the Milky Way's black hole sports such a jet today, it may have in the past.

The bubbles also may have formed as a result of gas outflows from a burst of star formation, perhaps the one that produced many massive star clusters in the Milky Way's central light-years several million years ago.

"In other galaxies, we see that starbursts can drive enormous gas outflows," said David Spergel at Princeton University in New Jersey22. "Whatever the energy source behind these huge bubbles may be, it is connected to many deep questions in astrophysics(天体物理学) ."

Finkbeiner noted that, in retrospect23(回顾) , hints of the bubbles appear in earlier spacecraft data, including the Germany-led Roentgen X-ray Satellite (ROSAT) and NASA's Wilkinson Microwave Anisotropy Probe (WMAP).



点击收听单词发音收听单词发音  

1 previously bkzzzC     
adv.以前,先前(地)
参考例句:
  • The bicycle tyre blew out at a previously damaged point.自行车胎在以前损坏过的地方又爆开了。
  • Let me digress for a moment and explain what had happened previously.让我岔开一会儿,解释原先发生了什么。
2 milky JD0xg     
adj.牛奶的,多奶的;乳白色的
参考例句:
  • Alexander always has milky coffee at lunchtime.亚历山大总是在午餐时喝掺奶的咖啡。
  • I like a hot milky drink at bedtime.我喜欢睡前喝杯热奶饮料。
3 eruption UomxV     
n.火山爆发;(战争等)爆发;(疾病等)发作
参考例句:
  • The temple was destroyed in the violent eruption of 1470 BC.庙宇在公元前1470年猛烈的火山爆发中摧毁了。
  • The eruption of a volcano is spontaneous.火山的爆发是自发的。
4 galaxy OhoxB     
n.星系;银河系;一群(杰出或著名的人物)
参考例句:
  • The earth is one of the planets in the Galaxy.地球是银河系中的星球之一。
  • The company has a galaxy of talent.该公司拥有一批优秀的人才。
5 astronomer DOEyh     
n.天文学家
参考例句:
  • A new star attracted the notice of the astronomer.新发现的一颗星引起了那位天文学家的注意。
  • He is reputed to have been a good astronomer.他以一个优秀的天文学者闻名于世。
6 fully Gfuzd     
adv.完全地,全部地,彻底地;充分地
参考例句:
  • The doctor asked me to breathe in,then to breathe out fully.医生让我先吸气,然后全部呼出。
  • They soon became fully integrated into the local community.他们很快就完全融入了当地人的圈子。
7 constellation CptzI     
n.星座n.灿烂的一群
参考例句:
  • A constellation is a pattern of stars as seen from the earth. 一个星座只是从地球上看到的某些恒星的一种样子。
  • The Big Dipper is not by itself a constellation. 北斗七星本身不是一个星座。
8 detector svnxk     
n.发觉者,探测器
参考例句:
  • The detector is housed in a streamlined cylindrical container.探测器安装在流线型圆柱形容器内。
  • Please walk through the metal detector.请走过金属检测器。
9 eluded 8afea5b7a29fab905a2d34ae6f94a05f     
v.(尤指机敏地)避开( elude的过去式和过去分词 );逃避;躲避;使达不到
参考例句:
  • The sly fox nimbly eluded the dogs. 那只狡猾的狐狸灵活地躲避开那群狗。 来自《现代汉英综合大词典》
  • The criminal eluded the police. 那个罪犯甩掉了警察的追捕。 来自《现代英汉综合大词典》
10 astronomers 569155f16962e086bd7de77deceefcbd     
n.天文学者,天文学家( astronomer的名词复数 )
参考例句:
  • Astronomers can accurately foretell the date,time,and length of future eclipses. 天文学家能精确地预告未来日食月食的日期、时刻和时长。 来自《简明英汉词典》
  • Astronomers used to ask why only Saturn has rings. 天文学家们过去一直感到奇怪,为什么只有土星有光环。 来自《简明英汉词典》
11 diffuse Al0zo     
v.扩散;传播;adj.冗长的;四散的,弥漫的
参考例句:
  • Direct light is better for reading than diffuse light.直射光比漫射光更有利于阅读。
  • His talk was so diffuse that I missed his point.他的谈话漫无边际,我抓不住他的要点。
12 emission vjnz4     
n.发出物,散发物;发出,散发
参考例句:
  • Rigorous measures will be taken to reduce the total pollutant emission.采取严格有力措施,降低污染物排放总量。
  • Finally,the way to effectively control particulate emission is pointed out.最后,指出有效降低颗粒排放的方向。
13 emissions 1a87f8769eb755734e056efecb5e2da9     
排放物( emission的名词复数 ); 散发物(尤指气体)
参考例句:
  • Most scientists accept that climate change is linked to carbon emissions. 大多数科学家都相信气候变化与排放的含碳气体有关。
  • Dangerous emissions radiate from plutonium. 危险的辐射物从钚放散出来。
14 inverse GR6zs     
adj.相反的,倒转的,反转的;n.相反之物;v.倒转
参考例句:
  • Evil is the inverse of good.恶是善的反面。
  • When the direct approach failed he tried the inverse.当直接方法失败时,他尝试相反的做法。
15 scattering 91b52389e84f945a976e96cd577a4e0c     
n.[物]散射;散乱,分散;在媒介质中的散播adj.散乱的;分散在不同范围的;广泛扩散的;(选票)数量分散的v.散射(scatter的ing形式);散布;驱散
参考例句:
  • The child felle into a rage and began scattering its toys about. 这孩子突发狂怒,把玩具扔得满地都是。 来自《简明英汉词典》
  • The farmers are scattering seed. 农夫们在播种。 来自《简明英汉词典》
16 infrared dx0yp     
adj./n.红外线(的)
参考例句:
  • Infrared is widely used in industry and medical science.红外线广泛应用于工业和医学科学。
  • Infrared radiation has wavelengths longer than those of visible light.红外辐射的波长比可见光的波长长。
17 spectrum Trhy6     
n.谱,光谱,频谱;范围,幅度,系列
参考例句:
  • This is a kind of atomic spectrum.这是一种原子光谱。
  • We have known much of the constitution of the solar spectrum.关于太阳光谱的构成,我们已了解不少。
18 relatively bkqzS3     
adv.比较...地,相对地
参考例句:
  • The rabbit is a relatively recent introduction in Australia.兔子是相对较新引入澳大利亚的物种。
  • The operation was relatively painless.手术相对来说不痛。
19 remains 1kMzTy     
n.剩余物,残留物;遗体,遗迹
参考例句:
  • He ate the remains of food hungrily.他狼吞虎咽地吃剩余的食物。
  • The remains of the meal were fed to the dog.残羹剩饭喂狗了。
20 noted 5n4zXc     
adj.著名的,知名的
参考例句:
  • The local hotel is noted for its good table.当地的那家酒店以餐食精美而著称。
  • Jim is noted for arriving late for work.吉姆上班迟到出了名。
21 galaxies fa8833b92b82bcb88ee3b3d7644caf77     
星系( galaxy的名词复数 ); 银河系; 一群(杰出或著名的人物)
参考例句:
  • Quasars are the highly energetic cores of distant galaxies. 类星体是遥远星系的极为活跃的核心体。
  • We still don't know how many galaxies there are in the universe. 我们还不知道宇宙中有多少个星系。
22 jersey Lp5zzo     
n.运动衫
参考例句:
  • He wears a cotton jersey when he plays football.他穿运动衫踢足球。
  • They were dressed alike in blue jersey and knickers.他们穿着一致,都是蓝色的运动衫和灯笼短裤。
23 retrospect xDeys     
n.回顾,追溯;v.回顾,回想,追溯
参考例句:
  • One's school life seems happier in retrospect than in reality.学校生活回忆起来显得比实际上要快乐。
  • In retrospect,it's easy to see why we were wrong.回顾过去就很容易明白我们的错处了。
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