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At four billion years old, the universe was still a child. |
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Thursday, scientists said they got their first peek at what that childhood looked like by measuring all of the light that was around at that time that's still traveling to us. |
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宇宙在歲數達四十億年的時候，還只算是個孩子。週四，科學家指出他們藉由測量現在才傳到地球的那個時代的所有光線，而首度窺見了宇宙童年時期的樣貌。 |
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It's what astronomers and cosmologists call extragalactic background light. |
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This includes light from stars that existed when the universe was even younger than four billion years old. |
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Researchers explain this can help them understand how stars formed and how galaxies evolved. |
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這是天文學家和宇宙學家所謂的銀河外背景光，包括在宇宙的歲數甚至還未達四十億年之時的恆星所發出的光芒。研究人員說明指出，這種光線能夠協助他們瞭解星體如何形成，以及銀河如何演化。 |
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"I think it's amazing to be able to probe our universe when it was so young, when the very first stars formed," said Marco Ajello, researcher at Stanford University and co-author of the study published in the journal Science. |
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「我認為能夠探究那麼年輕的宇宙是非常令人驚奇的事情，當時最早的星體才剛形成而已，」馬可•艾黑羅說，他是史丹福大學的研究員，也是刊登於《科學》期刊的那份研究的共同作者。 |
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The finding is important for estimating the number of smaller, fainter galaxies that current telescopes cannot detect. |
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The reason is that every telescope has limitations, especially in size. |
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Astronomers can use them to detect the big, luminous galaxies, but there are more galaxies that the tools will miss. |
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這項發現對於估計那些當前望遠鏡無法偵測到、較小也較黯淡的銀河數量而言很重要，原因是每一具望遠鏡都有其自身的限制，特別是在大小方面。天文學家可以使用望遠鏡偵測到龐大明亮的銀河，但有更多的銀河是這些工具偵測不到的。 |
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"Studying the extragalactic background light allows us to overcome this limitation, because the background light is the sum of the light produced by all galaxies, including the ones that are too faint to be detected individually by traditional methods," said Claude-Andre Faucher-Giguere, researcher in the Department of Astronomy at the University of California, Berkeley. |
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「研究銀河外背景光可讓我們克服這項限制，因為背景光是所有銀河發出的光芒的總和，包括那些亮度太暗，以致無法用傳統方法個別偵測到的銀河，」柏克萊加州大學天文學系研究員克勞安卓•佛雪吉格爾說。 |
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Scientists focused their efforts at high-energy gamma rays using NASA's Fermi Gamma-ray Space Telescope. |
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Specifically, they looked at "blazars," which are galactic nuclei that spew plasma jets associated with supermassive black holes. |
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科學家使用美國太空總署的費米伽瑪射線太空望遠鏡，專注於偵測高能伽瑪射線。他們特別要找的是「耀變體」，這種星系核會噴出與超大質量黑洞有關的電漿噴流。 |
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"These gamma-ray sources are like ‘lighthouses' and the starlight is like the fog," Ajello said. |
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Scientists know that starlight is absorbing the gamma rays when the "lighthouse" is dimmer. |
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「這些伽瑪射線來源就像『燈塔』，星光就像霧氣，」艾黑羅說。「燈塔」比較暗的話，科學家就知道星光吸收了伽瑪射線。 |
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Scientists can therefore add up the light from the galaxies they can detect, and compare that to the extragalactic background light. |
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This subtraction is a clue to how many galaxies they haven't yet directly detected with their telescopes, and how luminous they are. |
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因此，科學家即可將他們偵測得到的銀河的光度加總起來，再與銀河外背景光互相比較。兩者相減之後即可提供線索，讓科學家知道有多少銀河沒有被他們的望遠鏡直接偵測到，而且那些銀河又有多亮。 |
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