Now we know how much starlight the universehas ever created
現(xiàn)在我們知道宇宙創(chuàng)造了多少星光
一張經(jīng)過時間延遲拍攝的夜空照片，隨著時間的推移，顯示出恒星產(chǎn)生了多少光，即使是遙遠(yuǎn)的恒星。（照片：天空光輝項目）
When we look up at the night sky, it's darkyet filled with pinpoints of light. It comes to our eyes from nearby planetsand faraway stars. But it's worth remembering that the light we see fromplanets, and our moon (or other planets' moons) is all reflected. The onlyoriginal light comes from stars, like our sun, and that bounces off surfaces,creating more points of light.
當(dāng)我們仰望夜空時，它是黑暗的，但充滿了光點。映入我們眼中的光就來自附近的行星和遙遠(yuǎn)的恒星。但是值得注意的是，我們從行星上看到的光，以及我們的月亮（或者其他行星的衛(wèi)星）的光都被反射出來的。唯一的原始光都來自恒星，比如我們的太陽，光從行星或衛(wèi)星表面反射，產(chǎn)生更多的光點。
Recently, all that starlight was added up.
最近，我們所有星光都加起來了。
'From data collected by the Fermitelescope, we were able to measure the entire amount of starlight ever emitted.This has never been done before,' lead study author and Clemson Universityastrophysicist Marco Ajello told CNN. 'Most of this light is emitted bystars that live in galaxies. Every single star that has existed has contributedto this emission, and we can use it to learn all the details about starformation and evolution and galaxy evolution.'
這項研究成果的主要作者、克萊姆森大學(xué)天體物理學(xué)家馬爾科·阿耶洛告訴美國有線電視新聞網(wǎng)說：“從費(fèi)米望遠(yuǎn)鏡收集的數(shù)據(jù)，我們能夠測量出曾經(jīng)發(fā)射的全部星光。以前從未有人這樣做過。這些光大部分是由運(yùn)行在星系中的恒星發(fā)出的。每一顆已經(jīng)存在的恒星都產(chǎn)生了這種輻射，而我們可以利用它來了解恒星的形成和演化，以及星系演化的所有細(xì)節(jié)?！?/span>
The grand total? Published in the journalScience, the number is huge, so it's expressed in a powers-of-ten notation:It's 4x10^84.
總計是多少呢？結(jié)果發(fā)表在《科學(xué)》雜志上，數(shù)字是巨大的，因此用十次方符號表示就是：4x1084。
That's 4 followed by 84 zeros of particlesof visible light (photons), which comes from the estimated 2 trillion galaxiesand the trillion trillion stars (not a type-o!) within them.
是在4后面加上84個零的可見光粒子（光子），它們來自估計的2萬億個星系以及其中的萬萬萬億顆恒星（不是o型）。
To get to the starlight quantity number,scientists had collected data for nine years from NASA's Fermi Gamma-ray SpaceTelescope. But that scope didn't just scan around and collect light outputinformation, since light from distant stars is too hard to measure from Earth.Instead, the Fermi telescope gathered information on gamma rays. Thissuper-energetic form of light is easier to measure than visible light since theenergy is a billion times higher.
為了得到星光數(shù)量，科學(xué)家們已經(jīng)利用美國國家航空航天局的費(fèi)米伽馬射線太空望遠(yuǎn)鏡收集了九年的數(shù)據(jù)。但是這個望遠(yuǎn)鏡不僅僅是四處掃描并收集光輸出信息，因為來自遙遠(yuǎn)恒星的光很難從地球上測量出來。相反，費(fèi)米望遠(yuǎn)鏡收集的是伽馬射線的信息。這種超高能形式的光比可見光更容易測量，因為其能量是可見光的十億倍。
But Fermi wasn't gathering gamma raysdirectly either. Rather, it looked at how those gammas reflect, refract andabsorb into the extragalactic background light of the universe, which Ajellorefers to as 'fog' below, and NASA characterizes as 'a cosmicfog composed of all the ultraviolet, visible and infrared light stars havecreated over the universe’s history.'
但是費(fèi)米望遠(yuǎn)鏡也不是直接收集伽馬射線。相反，它研究了這些伽馬射線是如何反射、折射和吸收到宇宙的星系外背景光中的，阿耶洛在下文將其稱之為“霧”，而美國國家航空航天局形容它為“一種宇宙霧，由宇宙歷史上所有紫外線、可見光和紅外光恒星組成?！?/span>
This map of the entire sky shows thelocation of 739 blazars used in the Fermi Gamma-ray Space Telescope’smeasurement of the extragalactic background light (EBL).
這張整個天空的地圖，顯示了費(fèi)米伽馬射線太空望遠(yuǎn)鏡測量星系外背景光（EBL）時的739個黑洞的位置。
The background shows the sky as it appearsin gamma rays with energies above 10 billion electron volts, constructed fromnine years of observations by Fermi’s Large Area Telescope. The plane of ourMilky Way galaxy runs along the middle of the plot. (Photo: CourtesyNASA/DOE/Fermi LAT Collaboration)
該背景顯示的是能量超過100億電子伏特的伽馬射線中出現(xiàn)的天空，這是費(fèi)米大口徑望遠(yuǎn)鏡歷時九年的觀測結(jié)果。我們的銀河系的平面沿圖的中間延伸。（照片：由美國航空航天局/能源部/費(fèi)米大口徑望遠(yuǎn)鏡合作提供）
This type of measurement allows scientiststo see back in time.
這種類型的測量可以讓科學(xué)家們及時回看。
'Gamma-ray photons traveling through afog of starlight have a large probability of being absorbed,' Ajello toldCNN. 'By measuring how many photons have been absorbed, we were able tomeasure how thick the fog was and also measure, as a function of time, how muchlight there was in the entire range of wavelengths.'
阿耶洛告訴美國有線電視新聞網(wǎng)稱：“穿過星光霧的伽馬射線光子很有可能被吸收。通過測量吸收了多少光子，我們能夠測量霧的厚度，還能測量整個波長范圍內(nèi)有多少光，這是一個時間的函數(shù)?！?/span>
It may sound like a game of telephone, butfinding these echoes of what happened a billion years ago, 2 billion years ago,and beyond is what's necessary to determine how much light has shone in thepast.
這聽起來像是一場電話游戲，但是找到10億年前、20億年前以及以后發(fā)生的事情的回聲，是確定過去有多少光射出的必要條件。
And of course, the light continues on frommoment of calculation. It's estimated that seven new stars are born in theMilky Way galaxy every year — just a few small buckets to add to that sea oflight above you.
當(dāng)然，光要從亮起的那一刻就計算的。據(jù)估算，每年都會有七顆新的恒星誕生在銀河系中——只需幾個小桶就能為你頭頂上方的光之海增添光彩。
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