天文学家发现最远的类星体
文章来源:未知 文章作者:enread 发布时间:2011-06-30 01:16 字体: [ ]  进入论坛
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"This quasar(类星体) is a vital probe of the early Universe. It is a very rare object that will help us to understand how supermassive black holes grew a few hundred million years after the Big Bang," says Stephen Warren, the study's team leader. Quasars are very bright, distant galaxies1 that are believed to be powered by supermassive black holes at their centres. Their brilliance2(光辉,才华) makes them powerful beacons3 that may help to probe the era when the first stars and galaxies were forming. The newly discovered quasar is so far away that its light probes the last part of the reionisation era.

The quasar that has just been found, named ULAS J1120+0641, is seen as it was only 770 million years after the Big Bang (redshift 7.1). It took 12.9 billion years for its light to reach us.

Although more distant objects have been confirmed (such as a gamma-ray burst at redshift 8.2, eso0917 - http://www.eso.org/public/news/eso0917/, and a galaxy4 at redshift 8.6, eso1041 - http://www.eso.org/public/news/eso1041/), the newly discovered quasar is hundreds of times brighter than these. Amongst objects bright enough to be studied in detail, this is the most distant by a large margin5.

The next most-distant quasar is seen as it was 870 million years after the Big Bang (redshift 6.4). Similar objects further away cannot be found in visible-light surveys because their light, stretched by the expansion of the Universe, falls mostly in the infrared6 part of the spectrum7(光谱,范围) by the time it gets to Earth. The European UKIRT Infrared Deep Sky Survey (UKIDSS) which uses the UK's dedicated8 infrared telescope in Hawaii was designed to solve this problem. The team of astronomers9 hunted through millions of objects in the UKIDSS database to find those that could be the long-sought distant quasars, and eventually struck gold.

"It took us five years to find this object," explains Bram Venemans, one of the authors of the study. "We were looking for a quasar with redshift higher than 6.5. Finding one that is this far away, at a redshift higher than 7, was an exciting surprise. By peering deep into the reionisation era, this quasar provides a unique opportunity to explore a 100-million-year window in the history of the cosmos10 that was previously11 out of reach."

The distance to the quasar was determined12 from observations made with the FORS2 instrument on ESO's Very Large Telescope (VLT) and instruments on the Gemini North Telescope. Because the object is comparatively bright it is possible to take a spectrum of it (which involves splitting the light from the object into its component13 colours). This technique allowed the astronomers to find out quite a lot about the quasar.

These observations showed that the mass of the black hole at the centre of ULAS J1120+0641 is about two billion times that of the Sun. This very high mass is hard to explain so early on after the Big Bang. Current theories for the growth of supermassive black holes predict a slow build-up in mass as the compact object pulls in matter from its surroundings.

"We think there are only about 100 bright quasars with redshift higher than 7 over the whole sky," concludes Daniel Mortlock, the leading author of the paper. "Finding this object required a painstaking14(艰苦的,勤勉的) search, but it was worth the effort to be able to unravel15(解开,阐明) some of the mysteries of the early Universe."



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1 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。
2 brilliance 1svzs     
n.光辉,辉煌,壮丽,(卓越的)才华,才智
参考例句:
  • I was totally amazed by the brilliance of her paintings.她的绘画才能令我惊歎不已。
  • The gorgeous costume added to the brilliance of the dance.华丽的服装使舞蹈更加光彩夺目。
3 beacons dfb02f84b16e33c347ba417c44745ea7     
灯塔( beacon的名词复数 ); 烽火; 指路明灯; 无线电台或发射台
参考例句:
  • A chain of beacons was lit across the region. 整个地区点起了一系列灯塔。
  • Lighthouse and beacons flash at night. 晚上灯塔与信号台闪着光。
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 margin 67Mzp     
n.页边空白;差额;余地,余裕;边,边缘
参考例句:
  • We allowed a margin of 20 minutes in catching the train.我们有20分钟的余地赶火车。
  • The village is situated at the margin of a forest.村子位于森林的边缘。
6 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。
7 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。
8 dedicated duHzy2     
adj.一心一意的;献身的;热诚的
参考例句:
  • He dedicated his life to the cause of education.他献身于教育事业。
  • His whole energies are dedicated to improve the design.他的全部精力都放在改进这项设计上了。
9 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》
10 cosmos pn2yT     
n.宇宙;秩序,和谐
参考例句:
  • Our world is but a small part of the cosmos.我们的世界仅仅是宇宙的一小部分而已。
  • Is there any other intelligent life elsewhere in the cosmos?在宇宙的其他星球上还存在别的有智慧的生物吗?
11 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。
12 determined duszmP     
adj.坚定的;有决心的
参考例句:
  • I have determined on going to Tibet after graduation.我已决定毕业后去西藏。
  • He determined to view the rooms behind the office.他决定查看一下办公室后面的房间。
13 component epSzv     
n.组成部分,成分,元件;adj.组成的,合成的
参考例句:
  • Each component is carefully checked before assembly.每个零件在装配前都经过仔细检查。
  • Blade and handle are the component parts of a knife.刀身和刀柄是一把刀的组成部分。
14 painstaking 6A6yz     
adj.苦干的;艰苦的,费力的,刻苦的
参考例句:
  • She is not very clever but she is painstaking.她并不很聪明,但肯下苦功夫。
  • Through years of our painstaking efforts,we have at last achieved what we have today.大家经过多少年的努力,才取得今天的成绩。
15 unravel Ajzwo     
v.弄清楚(秘密);拆开,解开,松开
参考例句:
  • He was good with his hands and could unravel a knot or untangle yarn that others wouldn't even attempt.他的手很灵巧,其他人甚至都不敢尝试的一些难解的绳结或缠在一起的纱线,他都能解开。
  • This is the attitude that led him to unravel a mystery that long puzzled Chinese historians.正是这种态度使他解决了长期以来使中国历史学家们大惑不解的谜。
TAG标签: stars universe quasar
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