天文学家首次发现新星伽玛射线-凯发k8官网

天文学家首次发现新星伽玛射线
文章来源:未知 文章作者:meng 发布时间:2010-08-13 00:04 字体: [ ] 
(单词翻译:双击或拖选)

1 using nasa's fermi gamma-ray space telescope have detected gamma-rays from a nova(新星) for the first time, a finding that 2(震惊) observers and theorists alike. the discovery overturns the notion that novae explosions lack the power to emit such high-energy radiation. a nova is a sudden, short-lived brightening of an otherwise inconspicuous(不显眼的) star. the outburst occurs when a white 3(白矮星) in a 4(二进制的,二元的) system erupts in an enormous thermonuclear(热核的) explosion.

"in human terms, this was an immensely powerful 5, equivalent to about 1,000 times the energy emitted by the sun every year," said elizabeth hays, a fermi deputy project scientist at nasa's goddard space flight center in greenbelt, md. "but compared to other cosmic events fermi sees, it was quite modest. we're amazed that fermi detected it so strongly."

gamma rays are the most energetic form of light, and fermi's large area telescope (lat) detected the nova for 15 days. scientists believe the 6 arose as a million-mile-per-hour shock wave raced from the site of the explosion.

a paper detailing the discovery will appear in the aug. 13 edition of the journal science.

the story opened in japan during the predawn(黎明前的) hours of march 11, when amateur(业余的,外行的) astronomers koichi nishiyama and fujio kabashima in miyaki-cho, 7 prefecture, imaged a dramatic change in the brightness of a star in the 8(星座) cygnus. they realized that the star, known as v407 cyg, was 10 times brighter than in an image they had taken three days earlier.

the team relayed the nova discovery to hiroyuki maehara at kyoto university, who notified astronomers around the world for follow-up observations. before this report became widely available, the outburst was independently reported by three other japanese amateurs: tadashi kojima, tsumagoi-mura agatsuma-gun, gunma prefecture; kazuo sakaniwa, higashichikuma-gun, nagano prefecture; and akihiko tago, tsuyama-shi, okayama prefecture.

"a few days later, automatic processing of data from fermi's lat alerted us to a new high-energy gamma-ray source at the same location as the nova," said teddy cheung, an astrophysicist(天体物理学家) at the 9 research laboratory (nrl) in washington, d.c., and the lead author of the nova study. "when we looked closer, we found that the lat had detected the first gamma rays at about the same time as the nova's discovery."

v407 cyg lies 9,000 light-years away. the system is a so-called 10(共生的) binary containing a compact white dwarf and a red giant star about 500 times the size of the sun.

"the red giant is so 11 that its 12(最外面的) atmosphere is just leaking away into space," said adam hill at joseph fourier university in grenoble, france. the phenomenon is similar to the solar wind produced by the sun, but the flow is much stronger. "each decade, the red giant sheds enough hydrogen gas to equal the mass of earth," he added.

the white dwarf 13 and captures some of this gas, which accumulates on its surface. as the gas piles on for decades to centuries, it eventually becomes hot and 14 enough to fuse into helium. this energy-producing process triggers a 15 reaction that explodes the accumulated gas.

the white dwarf itself, however, 16 intact.

the blast created a hot, dense expanding shell called a shock front, composed of high-speed particles, ionized gas and magnetic fields. according to an early 17 obtained by 18 buil at castanet tolosan 19, france, the nova's shock wave expanded at 7 million miles per hour -- or nearly 1 percent the speed of light.

the magnetic fields trapped particles within the shell and whipped them up to tremendous energies. before they could escape, the particles had reached 20(速度) near the speed of light. scientists say that the gamma rays likely resulted when these accelerated particles smashed into the red giant's wind.

"we know that the remnants of much more powerful supernova explosions can trap and accelerate particles like this, but no one suspected that the magnetic fields in novae were strong enough to do it as well," said nrl's soebur razzaque.

supernovae remnants endure for 100,000 years and affect regions of space thousands of light-years across.

kent wood at nrl compares 21 studies of supernova remnants to looking at static images in a photo album. "it takes thousands of years for supernova remnants to evolve, but with this nova we've watched the same kinds of changes over just a few days," he said. "we've gone from a photo album to a time-lapse movie."



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1 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》
2 735ec6d53723be15b1737edd89183ec2     
adj. 震惊的,惊讶的 动词stun的过去式和过去分词
参考例句:
  • the fall stunned me for a moment. 那一下摔得我昏迷了片刻。
  • the leaders of the kopper company were then stunned speechless. 科伯公司的领导们当时被惊得目瞪口呆。
3 ekjzh     
n.矮子,侏儒,矮小的动植物;vt.使…矮小
参考例句:
  • the dwarf's long arms were not proportional to his height.那侏儒的长臂与他的身高不成比例。
  • the dwarf shrugged his shoulders and shook his head. 矮子耸耸肩膀,摇摇头。
4 jybzwz     
adj.二,双;二进制的;n.双(体);联星
参考例句:
  • computers operate using binary numbers.计算机运行运用二进位制。
  • let us try converting the number itself to binary.我们试一试,把这个数本身变成二进制数。
5 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。
6 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。
7 acez4     
n.(尤指中世纪北欧海盗的)故事,英雄传奇
参考例句:
  • the saga of flight 19 is probably the most repeated story about the bermuda triangle.飞行19中队的传说或许是有关百慕大三角最重复的故事。
  • the novel depicts the saga of a family.小说描绘了一个家族的传奇故事。
8 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。
9 h1lyu     
adj.海军的,军舰的,船的
参考例句:
  • he took part in a great naval battle.他参加了一次大海战。
  • the harbour is an important naval base.该港是一个重要的海军基地。
10 frbwr     
adj.共栖的,共生的
参考例句:
  • racing has always had a symbiotic relationship with betting.赛马总是与赌博相挂钩。
  • engineering completely new symbiotic relationship is obviously not an imminent possibility.筹划完全新的共生关系显然是可能性不大。
11 drcwl     
adj.肿大的,水涨的;v.使变大,肿胀
参考例句:
  • her legs had got swollen from standing up all day.因为整天站着,她的双腿已经肿了。
  • a mosquito had bitten her and her arm had swollen up.蚊子叮了她,她的手臂肿起来了。
12 w4fzc     
adj.最外面的,远离中心的
参考例句:
  • he fired and hit the outermost ring of the target.他开枪射中了靶子的最外一环。
  • the outermost electron is shielded from the nucleus.原子核对最外层电子的作用受到屏蔽。
13 3445ed8b5856a7dea04f0c0399409410     
(数学)截距( intercept的名词复数 )
参考例句:
  • it intercepts a portion of the light impinging on the photocell. 它遮住一部分照射在光电管上的光。
  • the pelletfilter intercepts the particulate matter. 颗粒过滤器将颗粒物进行拦截。
14 aonzx     
a.密集的,稠密的,浓密的;密度大的
参考例句:
  • the general ambushed his troops in the dense woods. 将军把部队埋伏在浓密的树林里。
  • the path was completely covered by the dense foliage. 小路被树叶厚厚地盖了一层。
15 jd4y5     
n.逃走的人,逃亡,亡命者;adj.逃亡的,逃走的
参考例句:
  • the police have not found the runaway to date.警察迄今没抓到逃犯。
  • he was praised for bringing up the runaway horse.他勒住了脱缰之马受到了表扬。
16 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。
17 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 kvbyl     
adj.基督教徒的;n.基督教徒
参考例句:
  • they always addressed each other by their christian name.他们总是以教名互相称呼。
  • his mother is a sincere christian.他母亲是个虔诚的基督教徒。
19 hrgzp     
n.天文台,气象台,瞭望台,观测台
参考例句:
  • guy's house was close to the observatory.盖伊的房子离天文台很近。
  • officials from greenwich observatory have the clock checked twice a day.格林威治天文台的职员们每天对大钟检查两次。
20 64d80206fdcbbf917808c5b00e0a8ff5     
n.速度( velocity的名词复数 );高速,快速
参考例句:
  • in experimenting we find out that sound travels with different velocities through different substances. 在实验中,我们发现声音以不同的速度通过不同的物质而传播。 来自《现代汉英综合大词典》
  • a gas in thermal equilibrium has particles of all velocities. 处于热平衡的气体,其粒子有一切速度。 来自辞典例句
21 ketyo     
adj.天文学的,(数字)极大的
参考例句:
  • he was an expert on ancient chinese astronomical literature.他是研究中国古代天文学文献的专家。
  • houses in the village are selling for astronomical prices.乡村的房价正在飙升。
tag标签: light radiation gamma
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