💫多金‘星’二代的成长史💫The Growth History ofMetal-Rich Young Generations
人们常说，每个人都来自星星的尘埃，从一颗繁星投胎来到这个世界，等修完了功课，最后再回到那夜空中闪烁的一点。
It is often said that everyone is made of star dust, our lives begin and ends with those twinkling things above.
嗯，这其实说的也没错，宇宙中大部分的金属都是在那些聚变 ’工厂’ – 恒星中产生的，包括我们体内的各种微量元素。
Well, that is actually partially true! The majority of metals made in this universe are produced in stars – the fusion factory, including those metal elements in our body.
图为来自欧洲航天局的银河系360度全览图，包括了南天球和北天球的星空，揭示了环绕我们这个小小蓝色星球的宇宙景观
The 360-degree panoramic image from ESO, covering the entire southern and northern celestial sphere, reveals the cosmic landscape that surrounds our tiny blue planet.
造‘金’工厂
The Metal Factory
科学家认为，当这些元素在恒星中形成时，它们最终会通过恒星风或恒星生命末期的爆炸扩散和混合到恒星周围的气体中。
It is thought that when the elements are made in stars, they eventually get diffused and mixed into the surrounding gas of the star through stellar wind or the explosion at the end-of-life.
然而，在最近的研究中发现，恒星对自己所生产金属的出口贸易是相当迅速的，而且产品比我们想象的要走得更远更‘星系化’。
However, recent studies have shown that, exporting the produced metal, in fact, is relatively quick and the products go much further than what was imagined.
大部分的金属甚至会离开星系，进入银河介质，也就是星系周围的气体（盘外/星际介质外与维里半径内的部分）；或者是星系间的介质，也就是星系间的气体部分。
The majority would actually leave the galaxy and move into the circumgalactic medium, which is the gas surrounding galaxies (outside disk/interstellar medium and inside the virial radii); or on to the intergalactic medium, which is the gas between galaxies.
要理解这些金属在产生后的活动轨迹，观察放射性同位素是一种有效的方法，因为它们的半衰期比非放射性粒子短得多，因此更容易在较短的时间内检测到它们的活动。
One way to monitor the activities of the metals after creation is the by observing the radioactive isotopes, since they have much shorter half-life than non-radioactive particles, hence easier to detect activities.
铝26 （Al 26）是银河系中相对常见的放射性同位素之一，所以也被选为了观测金属生产的金属元素。它的半衰期约为100万年，辐射线位于伽马射线能量区域，有1.8兆电子伏。
Aluminum 26 (Al 26), being one of the relatively common radioactive isotopes throughout the Milky Way, is normally the chosen material for metal production observation. It has a half-life of about 1 million years and an emission line at 1.8MeV, in the gamma ray energy band.
图为迄今为止最早被记录到的超新星（恒星生命结束时的爆炸），是最先由中国天文学家在公元185年发现的。图片结合四个望远镜的数据后组成了RCW86残骸的多波长视图。绿色和蓝色数据来自NASA Chandra X-ray 和ESA XMM-Newton天文台，黄色和红色数据来自NASA Spitzer Space 望远镜和WISE的广域红外巡天探测器。
The earliest recorded supernova （explosion at the end of a star's life），first seen by Chinese astronomers in A.D. 185. The image combined data from four telescopes to form a multi-wavelength view of the remains of RCW86. Green and blue data are from NASA's Chandra X-Ray and ESA XMM-Newton observatories, while yellow and red data are from NASA's Spitzer Space Telescope and WISE's Wide-field Infrared Survey Explorer.
从哪来？要去哪？
From where? Where to?
由于铝26在星系中的整体分布呈自然的团块状，它被认为是主要在大质量恒星中产生的。是的，又是这些大星星们在刷存在感!
Due to Al 26's overall spread in the galaxy - clumpy yet nature, it is understood that Al 26 is produced mainly in massive stars only. Yes, the big ones get the attention again！
尽管这些恒星很大只，它们其实代表了一个相对年轻的恒星群体，目前主要形成位置在远离中心的星系盘中，而不是星系中心的凸起部分。
However, though those stars are big, they represent a young stellar population, which are currently forming in the disc of the galaxy, instead of the bulge, away from the center.
在它们的一生中，它们会不断地通过强烈的恒星风喷射出内核产生的金属，最后再在生命结束时产生巨大的超新星。
Throughout their life, they would continuously eject metal via intense stellar winds and produce massive supernova at the end.
图为NASA哈勃望远镜拍到的Wolf-Rayet Star 124，是一颗少见的巨型恒星。平均地球30倍大小的热气团们正不断地被猛烈的恒星风驱逐。
Wolf-Rayet Srar 124 from NASA's Hubble. Being a rare massive star, glowing gas globs each 30 times more massive than the Earth are being expelled by violent stellar winds.
说了这么多，可能觉得这些事情离我们的都相当的遥远，但实际铝26也在我们脚下的地球表层中被探测到了。在一些早期形成的陨石中，科学已经发现了镁26（铝26的衰变产物），这表明我们附近曾经一定有大质量的恒星存在过，在它爆炸后的数万年后成为了我们太阳系和周围环境的一员。
Although all these ideas seem far far away, Al 26 have actually been measured and detected much closer to home. In some early-formed meteorites, Magnesium 26 (a decay product of Al 26) have been found, showing that massive stars must have been nearby in order to enrich the gas that formed our Solar System.
要让同位素在银河系中扩散并在形成我们的冷气体中留下痕迹，这些大质量恒星一定有过超强的金属生产能力。
So, for the isotopes to both spread through the Milky Way and leave traces of it in the cold gases to form us, the massive stars must have very sufficient with the metal production.
大风吹，吹呀吹
The Wind
有了这些知识，一个由Martin G. H. Krause领导，成员来自英国和德国的科研小组，对铝26和其他金属物质在星系中的存在进行了进一步研究。对一个类似银河系的星系进行3D模拟，以研究该星系的化学演化。
With these knowledges in hand, a research team led by Martin G. H. Krause, based in the UK and Germany, sat up a 3D simulation of a Milky Way-like galaxy to study the chemical evolution, in particular the Al 26, in the galaxy.
模型是一个孤立盘状星系的星际介质3D流体力学模拟，模仿了引力势中静态暗物质的光晕，恒星膨胀区，圆盘和旋转旋臂。
The model is a set of 3D hydrodynamic simulations of the interstellar medium of an isolated disc galaxy set in a gravitational potential that represents the static dark matter halo, stellar bulge, disc and rotating spiral arms.
图为科学小组3D模型：左图呈现了铝26在星系中的密度分布；右图展现了星系的气体密度，以及马赫数等高线。两个模型中的地图均向每个方向延伸了20 kpc(大约银河系的半径)。
The team's 3D simulations: the left panel shows the density distribution of Al 26 in the galaxy; the right panel shows the gas density of the galaxy, along with the Mach number contours. Both maps extend 20 kpc (about the radius of the Milky Way) in each direction.
其中，模型的超级气泡（一种由星风从恒星表面的星尘或气体吹出的巨星气泡形状结构）是最后被注入到星系旋臂附近的预定位置的。在模型中代表了相当于100万个太阳质量的恒星形成区。模拟的是恒星形成一千万年后的能量、质量以及 铝26质量的状态，与银河系的自然过程时间相匹配。
Superbubbles, which are vast bubble shaped structures formed by winds blowing off gas and dust stars used to possess, were injected at predetermined positions near the spiral arms. There, they represent the star forming regions equivalent to a million solar mass, with energy, mass and Al 26 mass simulated to a state at 10 Myr after star formation, matching the natural process time of the Milky Way.
模拟中发现最主要的结果之一是，在恒星开始形成后不久，可以看到大规模的Al 26风和气体流动。一些甚至可以从源头延伸到20kpc（6.5万光年）外，途中与不同的物质混合，很快地丰富了星系周围的介质。
One of the main results found in this simulation is that large-scale winds of Al 26 and gas can be seen relatively soon after the star formations begin. With some winds extending up to 20kpc (65 thousand light years) away from the source, the processed materials mix with each other along the way and soon enrich the circumgalactic medium.
模型还表明，即使像银河系这样，恒星形成程度中等的星系，仍然会产生大量的恒星驱动风，影响周边的环境。
The simulation also suggests that even galaxies, like the Milky Way, with moderate star formation can still produce high volume of stellar-driven wind affecting surrounding environments.
另一个有趣的发现是，铝26风可以处于热期或冷期。与热气体一起的那些会随着气体离开银河系，在太空中闯荡，而与冷气体的那些只能留在家乡，最终形成下一代的恒星或其他天体，等待数十亿年后在我们的后花园中被发现。
Another interesting fact that the Al 26 winds can be either in a hot phase or a cold phase. The ones associated with the hot gas get to continue leaving the galaxy and explore further in space, while cold ones have to stay behind, which eventually form into stars and wait to be found in our back gardens billions of year later.
另外，基于已经形成的金属元素不会轻易消失，最近几代恒星的金属含量比前几代更高。铝 26气体的存在表明，富集的它们气体通常会迅速地重新形成恒星。
With the fact that more recent generations of stars have higher metalical contents than earlier generations, since metal elements were already made, the presence of Al 26 gas shows that that the enriched gas can be quickly remade into stars.
图为Toomre Q与温度的关系 - 冷气体可以形成恒星，而扩散的热气体则不能。Toomre Q代表了稳定性，其中log(Q)高于0的值是稳定的，不会崩塌，而低于0的值则可能崩溃。颜色代表质量，红色比蓝色的质量大。
Toomre Q versus temperature - cold gas remains available to form stars while the diffuse hot gas cannot. The Toomre Q represents a stability criterion where values of log(Q) above 0 are stable and will not collapse and values below can collapse. The colors represent mass, with red cells being more massive than blue cells.
神奇遗产在这里
Fantastic Heritage and Here to Find Them
从这些模拟中可以清楚地看到，大质量恒星在产生金属后，或用它们铸成‘闪耀’的放射性风烟囱，或将它们作为遗产，传给子孙后代。
From these simulations, it is clear that metal producing massive stars both form chimneys of ‘shiny’ radioactive winds during their lifetimes and pass some of their achievement as heritages to children and children’s children.
无论是哪种情况，铝 26的存在都表明这些过程发生得很快，并解释了星系周围金属气体的存在，以及年轻的第一星族（丰富金属的恒星，金属贫乏的恒星为第二星族）为何越来越‘多金’。
In either case, the presence of Al 26 indicates that these processes happen quickly and explain the enrichment of gas around galaxies and the increasing metallicity of young Population I stars (the metal-rich ones, population II stars are the metal-poor ones).
虽然这些本身并不是开创性的发现，
但它们是未来星系研究中关键的踏脚石！
对分析整个星系和宇宙的
过去与未来都至关重要！
Although these discoveries don’t seem groundbreaking on their own,
they are the key steppingstones for future studies
of galaxies and their environments,
vital for the analysis of
the whole galaxy and universe!
图为银河系的一幅艺术绘画，清晰地展示了星系的圆盘形状和星系旋臂的分布
An illustration of the Milky Way, showing clearly the disc structure and the spiral arms
图片来自 NASA, ESO 官网
文中部分英文信息参考来自英国和德国学者合作， 由 Martin G. H. Krause 带领的团队的 “
Galactic 26Al traces metal loss through hot chimneys" 论文
其余中英文内容为原创
Pictures from official website of NASA, ESO.
Parts are from “Galactic 26Al traces metal loss through hot chimneys" by the scientist team lead by Martin G. H. Krause from UK and Germany,
the rest of the Chinese and English content is original
