At the center of every galaxy is a supermassive black hole. Looking at the wider scale, is it possible that these gravity monsters influence the overall structure of our universe?
在每一星系中心，皆有個超大質量的黑洞。從更廣範圍來看，此些重力怪物可能影響，咱們宇宙的整體結構？
Using a new computer model, astrophysicists have recently calculated the ways in which black holes influence the distribution of dark matter, how heavy elements are produced and distributed throughout the cosmos, and where cosmic magnetic fields originate. The project, “Illustris – The Next Generation” (IllustrisTNG) is the most ambitious simulation of its kind to date.
使用一種新電腦模型，天體物理學家們最近已經計算了，黑洞影響暗物質分佈、在整個宇宙中，重元素如何產生與分佈及宇宙磁場起源於何處的諸多方式。該項“下一代揭示(Illustris)” (IllustrisTNG)計劃是迄今，這類最雄心勃勃的模擬。
By using supercomputers to explore the basic laws of physics, the simulations evolve a large piece of the Universe – roughly one billion light years across – from shortly after the Big Bang until the present day. Researchers use the simulations to study many of the outstanding puzzles of how our Universe, and the galaxies within it, came to be.
藉由使用超級電腦，來探索物理學的基本定律。此些模擬導出了，從宇宙大爆炸後不久到當今，大約橫跨十億光年的大片宇宙。研究人員們使用此些模擬，來研究咱們宇宙及在其內部星系，如何形成之諸多未解的謎團。
Our standard model for cosmology paints the picture of a Universe dominated by unknown forms of dark matter and dark energy. In order to test this scenario, we need precise predictions for how the night sky should appear.
咱們的宇宙論標準模型描繪了一個宇宙，是由未知形態之暗物質及暗能量左右的概念。為了驗證此腳本，咱們需要有關夜空，應如何出現的精確預測。
Because the light which reaches us arises from stars, diffuse gas, and accrete black holes, numerical simulations which directly evolve these three ‘baryonic’ (or normal matter) components, in addition to dark matter and dark energy, are crucial. These ‘hydrodynamical’ simulations, such as IllustrisTNG, have over the past few years become extremely powerful and predictive.
因為到達咱們的光，來自恆星、擴散的氣體及合生(吸積)的黑洞。因此，除了暗物質及暗能量之外，也直接導出此三種‘重子之’(也就是正常物質)成分的數值模擬，是至關重要的。這些‘流體動力學的’模擬(諸如IllustrisTNG)，在過去幾年間，已經成為極度強有力且預測性的模擬。
For instance, IllustrisTNG contains galaxies quite similar to the shape and size of real galaxies. The amount of stars in a given galaxy, how rapidly new stars are forming, and the balance between the ‘blue’ light of young stars and the redder light of old stars are all reasonable. For the first time, the detailed clustering pattern of galaxies in space has been shown to match large observational surveys.
譬如，IllustrisTNG包含與真實星系形狀及大小十分相似的星系。在已知星系中，恆星數量、新恆星多迅速形成及年輕恆星的‘藍’光與老恆星紅光之間的平衡，皆是有道理的。星系於太空中的詳細群集模式，已經首度被證實，與諸多大型觀測的勘查相一致。
We can also look at the most massive galaxies, which are thought to form through the collisions of numerous smaller galaxies. As these smaller systems are pulled together by the unrelenting attraction of gravity they are torn apart and scatter their stars in the vicinity of the massive galaxy.
咱們也能探究，被認為是透過諸多較小星系，碰撞形成的最大質量星系。當此些較小星系遭不停之重力吸引拖曳到一起時，它們瓦解並分散其恆星於大質量星系的附近。
These “stellar halos” are hard to spot and are only now starting to be observed, and IllustrisTNG provides concrete expectations for their structure. “Our predictions can be quantitatively checked by observers,” describes Dr. Annalisa Pillepich (MPIA). “How well their properties agree provides a critical test for our current theoretical ideas of how galaxies form.”
此些“恆星暈”(是指包含恆星之星系暈的組成部分)難以發現，目前才開始被觀察，而IllustrisTNG提供了有關其結構的諸多具體可能性。德國馬克斯普朗克天文研究所(MPIA：Max Planck Institute for Astronomy )的博士，Annalisa Pillepich記述：「她們的諸多預測能由，觀察者計量性地查核。它們的屬性有多一致，為咱們當前有關星系如何形成的理論概念，提供了一項不可或缺的驗證。」
The most important and, often, irreversible stage in the lifecycle of a galaxy is when it “quenches” star formation, and is no longer able to convert interstellar gas into young, bright stars. Before this happens, star-forming galaxies shine brightly in the blue light of their young stars. After an abrupt change, whose exact physical mechanism and origin is still debated, the galaxy slowly fades away and joins the class of ‘red and dead’ systems.
星系生命週期中，最重要且通常不可逆的階段是，當它“終止”恆星形成，不再能將星際氣體轉變成年輕、明亮的恆星時。在此發生之前，形成恆星的星系，以其年輕恆星的藍光，明亮地發光。在突然改變後，其確切的物理機制及原因，仍有爭議。星系會緩慢變暗淡，而加入‘紅色且死亡’之類的星系。
“IllustrisTNG clearly demonstrates that the only physical mechanism capable of extinguishing the star formation in these large galaxies are supermassive black holes,” explains Dr. Dylan Nelson (MPA). “These black holes release huge amounts of energy and drive ultrafast outflows of gas which can reach up to 10% the speed of light. The net result affects the entire stellar system of the galaxy, which can be billions of times larger than the comparably small black hole itself.”
馬克斯普朗克天體物理研究所(MPA：Max Planck Institute for Astrophysics) Dylan Nelson博士解釋：「IllustrisTNG清楚證實，在這些大星系中，能使恆星形成消聲匿跡的唯一物理機制，是超大質量黑洞。此些黑洞釋放出大量能量，並驅動可高達到10％光速的超快速氣體外流。最終結果影響了，比相較上小黑洞本身，會是更大數十億倍之星系的整個恆星系。」
“It is noteworthy that we can accurately predict the influence of supermassive black holes on the distribution of matter out to large scales,” says principal investigator Prof. Volker Springel (HITS). “This is crucial for reliably interpreting many forthcoming measurements from large observational programs.”
首要調查研究員，德國海德堡理論學研究所(HITS：Heidelberg Institute for Theoretical Studies)教授，Volker Springel宣稱：「值得注意的是，他們能精確預測，超大質量黑洞對物質大規模分佈的影響。就可靠解釋來自大型觀測計劃之諸多即將到來的測量而言，這是不可或缺的。」
To do so, the researchers developed a particularly efficient version of their highly parallel moving-mesh code AREPO and used it on the Hazel Hen machine at the High-Performance Computing Center Stuttgart – Germany’s fastest supercomputer.
為此，這些研究人員開發了一種，其高度並行的移動網格代碼AREPO(用於模擬流體動力學宇宙論的代碼)之特別有效率的版本，並將其用於斯圖加高性能計算中心的Hazel Hen計算機上，這是德國最快的超級電腦。
IllustrisTNG is the largest such project ever undertaken, and used 24,000 processors for more than two months to follow the simultaneous formation of millions of galaxies, producing more than 500 terabytes of data. The total time spent on the largest simulation so far was 35 million CPU hours, which would take 10,000 desktop computers roughly 1,000 years to accomplish.
IllustrisTNG是有史以來，被進行的最大此類計劃。使用了2萬4千個處理器達兩個多月，產生了超過500兆位元的數據，來瞭解數百萬個星系的同時形成。到目前為止，花在該項大型模擬的總時間是，3500萬中央處理器(CPU：Central Processing Unit)小時，這將需要1萬台桌上型電腦，大約1千年來能完成。
“Thanks to the German Gauss Centre for Supercomputing, we have been able to redefine the state of the art in this field,” explains Volker Springel. “Analyzing the new simulations will keep us busy for years to come, and it promises many exciting new insights into different astrophysical processes.”
Volker Springel解釋：「由於德國高斯超級計算中心，他們已經能重新定義該方法，在此領域的狀態。分析此些新模擬，將使他們在未來持續忙碌幾年，且具有深入不同天體物理過程之諸多令人振奮的新洞察力。」
原文網址：https://blog.oup.com/2018/03/how-do-black-holes-shape-cosmos/
翻譯：許東榮
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