Astronomers use a gravitational lens to find the most distant disk galaxy
天文學家們使用重力透鏡，來找尋最遙遠的圓盤狀星系。
Astronomers at the Max Planck Institute for Astrophysics, using the Atacama Large Millimeter/submillimeter Array (ALMA), have revealed an extremely distant and therefore very young galaxy that looks surprisingly like our Milky Way. The galaxy is so far away its light has taken more than 12 billion years to reach us: we see it as it was when the Universe was just 1.4 billion years old.
使用阿塔卡馬大型毫米/次毫米波陣列(ALMA)射電望遠鏡，德國馬克斯普朗克天體物理學研究所的天文學家們，業已揭露一處非常遙遠，且看起來出人意外地像咱們銀河系之非常年幼的星系。該星系距離非常遙遠，其到達咱們的光已經花了120多億年。我們看到的是，當宇宙只有14億歲時的它。
It is also surprisingly unchaotic, contradicting theories that all galaxies in the early Universe were turbulent and unstable. This unexpected discovery challenges our understanding of how galaxies form, giving new insights into the past of our Universe.
也令人訝異的是不紊亂，這與初期宇宙中，所有星系是紊亂、不穩定的理論相悖。此出乎意料的發現挑戰了，人們有關星系如何形成的理解，這提供了諸多有關咱們宇宙之過去的新洞察力。
圖1. 宇宙環：使用ALMA的天文學家們已經揭露一處，看起來出人意外地像咱們銀河系的非常遙遠星系。該SPT0418-47星系重力上遭到鄰近星系的透鏡作用，以一種所謂“愛因斯坦環”之近乎完美的光環出現於蒼穹中。
“This result represents a breakthrough in the field of galaxy formation, showing that the structures that we observe in nearby spiral galaxies and in our Milky Way were already in place 12 billion years ago,” says Francesca Rizzo, PhD student from the Max Planck Institute for Astrophysics in Germany, who led the research published today in Nature.
領導該項2020年8月發表於《自然》期刊之研究，來自德國馬克斯普朗克天體物理學研究所的博士生，Francesca Rizzo宣稱：「此研究結果代表了，在星系形成領域方面的一項突破。顯示，人們在鄰近之螺旋星系及咱們銀河系中，觀察到的結構，120億年前已經存在。」
While the galaxy the astronomers studied, called SPT0418-47, does not appear to have spiral arms, it has at least two features typical of our Milky Way: a rotating disc and a bulge, the large group of stars packed tightly around the galactic centre. This is the first time a bulge has been seen this early in the history of the Universe, making SPT0418-47 the most distant Milky Way look-alike.
儘管，此些天文學家研究的星系(被稱為SPT0418-47)似乎沒有螺旋臂。不過，至少具有咱們銀河系典型的兩種特徵：旋轉的圓盤狀及鼓起的部分，大群的恒星緊緊群聚於該星系中心周遭。這是宇宙史上，曾經被發現之首度這麼早的鼓起部分，這使得SPT0418-47看起來像最遙遠的銀河系。
“The big surprise was to find that this galaxy is actually quite similar to nearby galaxies, contrary to all expectations from the models and previous, less detailed, observations,” says co-author Filippo Fraternali, from the Kapteyn Astronomical Institute, University of Groningen in the Netherlands.
合撰人，來自荷蘭格羅寧根大學，卡普泰因天文學研究所的Filippo Fraternali宣稱：「大為令人訝異的事是，此星系實際上與鄰近的星系非常相似，與來自諸多模型及先前、較不詳細之觀察結果的所有預期相反。」
In the early Universe, young galaxies were still in the process of forming, so researchers expected them to be chaotic and lacking the distinct structures typical of more mature galaxies like the Milky Way.
在初期宇宙中，年輕的星系仍處於形成過程中。因此，研究人員們預期，它們會是紊亂，且缺乏像銀河系較成熟之星系典型的獨特結構。
Studying distant galaxies like SPT0418-47 is fundamental to our understanding of how galaxies formed and evolved. This galaxy is so far away we see it when the Universe was just 10% of its current age because its light took 12 billion years to reach Earth. By studying it, we are going back to a time when these baby galaxies were just beginning to develop.
研究像SPT0418-47的遙遠星系，是人們瞭解星系如何形成及演變的基礎。該星系距離非常遙遠，我們看到的是，當宇宙只是其當前年歲的10％時。因為，其到達地球的光，花費了120億年。藉由研究此星系，我們將回到此些年幼星系剛開始發展的時期。
Because these galaxies are so far away, detailed observations with even the most powerful telescopes are almost impossible as the galaxies appear small and faint. The team overcame this obstacle by using a nearby galaxy as a powerful magnifying glass — an effect known as gravitational lensing — allowing ALMA to see into the distant past in unprecedented detail.
由於距離很遙遠，此些星系顯得小且微弱。因此，即使利用最強大的望遠鏡，詳盡的觀測也幾乎不可能。藉由使用鄰近之星系作為一種，被通稱為重力透鏡作用的放大鏡，而使ALMA能以，前所未有之細節，觀察此遙遠星系的過去，團隊克服了此障礙。
In this effect, the gravitational pull from the nearby galaxy distorts and bends the light from the distant galaxy, causing it to appear misshapen and magnified.
在此作用中，來自鄰近星系的重力，扭曲且彎曲了來自此遙遠星系的光。這導致其出現變形及被放大。
圖2. 太空中的圓盤狀物：使用一種新電腦模型製作技術，該研究團隊從ALMA數據重建了此遙遠星系的真實形狀，及其氣體的活動，如圖所示。 此些觀測結果顯示，SPT0418-47是一處，具有中心鼓起部分及其物質圍繞中心旋轉的圓盤狀星系。
The gravitationally lensed, distant galaxy appears as a near-perfect ring of light around the nearby galaxy, thanks to their almost exact alignment. The research team reconstructed the distant galaxy’s true shape and the motion of its gas from the ALMA data using a new computer modelling technique. “When I first saw the reconstructed image of SPT0418-47 I could not believe it: a treasure chest was opening,” says Rizzo.
由於它們幾乎完全對齊，這種重力上起透鏡作用的遙遠星系，以圍繞該鄰近星系之近乎完美的光環出現。使用一種新電腦模型製作技術，該研究團隊從ALMA數據重建了，此遙遠星系的真實形狀及其氣體的活動。Rizzo宣稱：「當他第一次看到SPT0418-47的重建影像時，無法相信：被開啟的是一個寶藏箱。」
“What we found was quite puzzling; despite forming stars at a high rate, and therefore being the site of highly energetic processes, SPT0418-47 is the most well-ordered galaxy disc ever observed in the early Universe,” stated co-author Simona Vegetti, also from the Max Planck Institute for Astrophysics. “This result is quite unexpected and has important implications for how we think galaxies evolve."
合撰人，亦來自馬克斯普朗克天體物理學研究所的Simona Vegetti陳述：「她們所發現的，十分令人困惑。儘管，以高速率形成恆星，因此是極度高能過程的場所。不過，SPT0418-47是初早期宇宙中，曾被觀察到之最有秩序的星系盤。此研究結果是十分意想不到的，且就人們思考星系如何演變而言，具有諸多重要意涵。」
The astronomers note, however, that even though SPT0418-47 has a disc and other features similar to those of spiral galaxies we see today, they expect it to evolve into a galaxy very different from the Milky Way, and join the class of elliptical galaxies, another type of galaxies that, alongside the spirals, inhabit the Universe today.
不過，此些天文學家特別提及，即使SPT0418-47具有圓盤狀，及其他類似咱們當今看到之螺旋星系的諸多特徵。他們預期，其演變成加入橢圓星系之非常不同於銀河系的星系。這是除了螺旋星系之外，也存在於當今宇宙中的另一型星系。
This unexpected discovery suggests the early Universe may not be as chaotic as once believed and raises many questions on how a well-ordered galaxy could have formed so soon after the Big Bang. This ALMA finding follows the earlier discovery announced in May of a massive rotating disc seen at a similar distance.
該意想不到的發現暗示，初期宇宙可能不如曾經被認為般的紊亂。因此，引發了諸多有關，在宇宙大爆炸後不久，如何可能曾形成十分有秩序的星系。ALMA的此發現是繼2020年5月被宣布，在相似距離處發現之巨大旋轉盤的較早發現後。
SPT0418-47 is seen in finer detail, thanks to the lensing effect, and has a bulge in addition to a disc, making it even more similar to our present-day Milky Way than the one studied previously.
由於上述起透鏡作用的效應，SPT0418-47更詳細地被發現，因此除了圓盤狀之外，也具有鼓起的部分。這使其比先前研究過的星系，更類似咱們當前的銀河系。
Future studies, including with ESO’s Extremely Large Telescope, will seek to uncover how typical these ‘baby’ disc galaxies really are and whether they are commonly less chaotic than predicted, opening up new avenues for astronomers to discover how galaxies evolved.
未來包括使用歐洲南方天文台(ESO：European Southern Observatory)之超大型望遠鏡的諸多研究，將探索此些‘年幼’圓盤狀星系實際上有多典型，及是否它們普遍比預期的較不紊亂。這為天文學家們開啟了，諸多發現星系如何演變的新途徑。
原文網址：https://www.mpg.de/15267623/likeness-of-the-milky-way?c=2249
翻譯：許東榮
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