Now we know how much starlight the universehas ever created
现在我们知道宇宙创造了多少星光
一张经过时间延迟拍摄的夜空照片，随着时间的推移，显示出恒星产生了多少光，即使是遥远的恒星。（照片：天空光辉项目）
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.
当我们仰望夜空时，它是黑暗的，但充满了光点。映入我们眼中的光就来自附近的行星和遥远的恒星。但是值得注意的是，我们从行星上看到的光，以及我们的月亮（或者其他行星的卫星）的光都被反射出来的。唯一的原始光都来自恒星，比如我们的太阳，光从行星或卫星表面反射，产生更多的光点。
Recently, all that starlight was added up.
最近，我们所有星光都加起来了。
'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.'
这项研究成果的主要作者、克莱姆森大学天体物理学家马尔科·阿耶洛告诉美国有线电视新闻网说：“从费米望远镜收集的数据，我们能够测量出曾经发射的全部星光。以前从未有人这样做过。这些光大部分是由运行在星系中的恒星发出的。每一颗已经存在的恒星都产生了这种辐射，而我们可以利用它来了解恒星的形成和演化，以及星系演化的所有细节。”
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.
总计是多少呢？结果发表在《科学》杂志上，数字是巨大的，因此用十次方符号表示就是：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个零的可见光粒子（光子），它们来自估计的2万亿个星系以及其中的万万万亿颗恒星（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.
为了得到星光数量，科学家们已经利用美国国家航空航天局的费米伽马射线太空望远镜收集了九年的数据。但是这个望远镜不仅仅是四处扫描并收集光输出信息，因为来自遥远恒星的光很难从地球上测量出来。相反，费米望远镜收集的是伽马射线的信息。这种超高能形式的光比可见光更容易测量，因为其能量是可见光的十亿倍。
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.'
但是费米望远镜也不是直接收集伽马射线。相反，它研究了这些伽马射线是如何反射、折射和吸收到宇宙的星系外背景光中的，阿耶洛在下文将其称之为“雾”，而美国国家航空航天局形容它为“一种宇宙雾，由宇宙历史上所有紫外线、可见光和红外光恒星组成。”
这张整个天空的地图，显示了费米伽马射线太空望远镜测量星系外背景光（EBL）时的739个黑洞的位置。
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)
该背景显示的是能量超过100亿电子伏特的伽马射线中出现的天空，这是费米大口径望远镜历时九年的观测结果。我们的银河系的平面沿图的中间延伸。（照片：由美国航空航天局/能源部/费米大口径望远镜合作提供）
This type of measurement allows scientiststo see back in time.
这种类型的测量可以让科学家们及时回看。
'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.'
阿耶洛告诉美国有线电视新闻网称：“穿过星光雾的伽马射线光子很有可能被吸收。通过测量吸收了多少光子，我们能够测量雾的厚度，还能测量整个波长范围内有多少光，这是一个时间的函数。”
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.
这听起来像是一场电话游戏，但是找到10亿年前、20亿年前以及以后发生的事情的回声，是确定过去有多少光射出的必要条件。
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.
当然，光要从亮起的那一刻就计算的。据估算，每年都会有七颗新的恒星诞生在银河系中——只需几个小桶就能为你头顶上方的光之海增添光彩。
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