2011-02-23 08:50:45 | 人氣(491) | 回應(0) | 上一篇 | 下一篇

來自蟹狀星雲的γ-射線閃光

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The Crab nebula, shown here in a Hubble Space Telescope image, is the remnant of a supernova explosion so nearby that Chinese astrologers took note of it in AD 1054.

如原文中的哈伯太空望遠鏡圖像所示,此蟹狀星雲是一顆很鄰近,以至於中國占星家們在公元1054年注意到的超新星爆炸殘留物。

 
(圖援用自原文)

 

Powered by the rapidly spinning neutron star at its heart, the nebula shines with extraordinary luminosity at all photon energies from radio to TeV gammas.

由其中心處迅速旋轉的中子星所驅動,該星雲閃爍著從射電(radio)到兆(1012)電子伏特γ-射線之所有光子能量的特殊光度。

 

The apparent stability of the Crab’s brightness over that entire range has made it a convenient reference for calibrating astronomical instruments; the brightness of other sources is often quoted in “millicrabs.”

在上述能量範圍,此蟹狀星雲亮度的明顯穩定性,已經使其成為校準天文儀器的一種方便參考物。其他來源的亮度往往以數毫蟹被引用(The Crab is a unit of measurement used by astronomers. Most space-based telescopes rely on it!)

 

But now two teams that operate orbiting gamma-ray telescopes—the Italian Space Agency’s AGILE and NASA’s Fermi—have reported seeing powerful short-duration flaring of the Crab nebula at gamma energies ranging from 100 MeV to 1 GeV.

不過,目前(2011)意大利太空署的AGILE(Astrorivelatore Gamma a Immagini Leggero)及美國航太總署的Fermi兩支操縱繞軌運行之γ-射線望遠鏡的團隊,已經提出發現此蟹狀星雲,範圍從100 MeV1 GeVγ-射線能量的強烈短期閃爍報告。

 

Lasting a few days or weeks, and apparently occurring once or twice a year, the outbursts manifest synchrotron radiation by electrons and positrons in the nebula that have somehow been accelerated to extremely high energies on an astonishingly rapid time scale.

這種持續幾天或幾星期的閃爍,顯然每年發生一次或兩次。此些爆發證實了,由該星雲中因某種未知原因,在驚人的迅速時間尺度下,已經被加速到極高能量之電子及正電子產生的同步輻射。

 

The flares rudely challenge the prevailing theory of how charged particles are accelerated, very gradually, in shock fronts within supernova remnants. The theory goes back to Enrico Fermi’s 1949 attempt to explain the origins of cosmic rays.

此些閃光嚴重挑戰了帶電粒子,在超新星殘留物內部的震動前沿,如何極逐步被加速的盛行理論。該理論回溯到1949年,Enrico Fermi解釋宇宙射線起源的企圖。

 

Now the Crab has been put under close surveillance by orbiting x-ray and optical telescopes as well as AGILE and Fermi, in hopes of pinpointing longer-wavelength clues within the nebula during the next gamma outburst.

期待在下一次γ-射線爆發期間,能確切找出該星雲內部較長波長的線索,除了AGILEFermi之外,目前該蟹狀星雲一直在繞軌運行之X-射線及光學望遠鏡的密切監視下。

 

 

原文網址:http://physicstoday.scitation.org/do/10.1063/PT.4.0883/full/

翻譯:許東榮

台長: peregrine
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