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哈勃太空望远镜探测到矮星系的“保护罩”：麦哲伦日冕_我的网站
一 | By Anna Dalla Valle (CNS)-- Forward-looking mindset: whole-system and life cycle thinking My work is centred on the environmental sustainability of buildings over the entire life cycle and beyond in view of the circular economy: from design and construction to use and reuse, up to final disposal or, preferably, recovery for a second life. Here, the paradigm shift is twofold, because a whole-system thinking is needed not only to consider the entire life cycle, but also to envision what happens next. The ultimate goal is to minimize environmental impacts and to drive both sustainability and innovation. To be more explicit, the first shift involves keeping in mind the entire life cycle – from the early design stages – moving beyond the traditional focus on construction and energy efficiency during use. It is to select building products looking back to the supply chain, such as recycled content, locally sourced and bio-based solutions, while also looking ahead to performance decay, maintenance needs and the potential for extending service life. Moreover, the second shift press to move beyond the linear building process – as traditionally practiced – in which we extract raw materials, we build, we use, and eventually we demolish. Indeed, this model has reached its limits, undermining planetary resources with adverse environmental and social effects. Interconnected choices: designing decisions that create shared value A life cycle perspective matched with circularity inevitably challenges this linearity, wondering from the very beginning about what happens when assets become obsolete and fall into disuse, to design buildings as part of a continuous loop of resources. Accordingly, design, construction, daily use (energy and water consumption), maintenance, replacement and end-of-life turn out to be regarded not as isolated steps but interconnected with each other. In fact, at each stage, choices can either preserve or destroy value. For example, if construction solutions are carefully selected, they can be reused in the future, either in their entirety, as whole products, or through disassembly into components, or even by separating materials. In this way, they may maintain the same function (e.g. a window reused as it is) or serve different purposes (e.g. glass cullet used as input for glass wool insulation). If technological systems are designed flexibly, buildings can reach different business segments and host concurrently different activities, resulting easily adaptable from housing to office and vice versa, instead of being demolished. If building processes integrate digital tools, data can guide smarter decisions over decades, provided that data infrastructure is ensured, followed by constant monitoring and analysis of the collected data and the update and dissemination of results across industry and practitioners as well as policymakers. Thinking this way means making choices future-oriented, ready to embrace innovation while respecting planetary boundaries, namely limiting the environmental impact at every stage and in every region – to avoid burden shifting – not just at the beginning but along the whole (first-second) life cycle. Certainly, a demanding but exciting challenge: one I am proud to take on and in my little to contribute to. Beyond appearances: close-up process for understanding what lies behind In daily life, we often say to "look beyond appearances". Usually, this expression pertains to people, to underline the risk of avoiding judging someone solely by what can be seen. Now the interesting thing is that the same advice can be applied to architecture, obviously without undermining the importance of aesthetic beauty, at the core also of the New European Bauhaus initiative together with sustainability and inclusion. Nonetheless, as an architect expert in sustainable technology, I have learned to extend it to the built environment, by seeing buildings not merely as visible structures (walls, roofs, windows), but as living parts of a larger and complex system. In this sense, architecture can be compared to a plant. Plants are anchored in the soil by roots; buildings are anchored in the ground by foundations. Plants capture sunlight, absorb water, accommodate small animals, and interact with other organisms; buildings consume energy, deplete water, host human life, and interact with their surroundings. Both are deeply connected to their ecosystem. However, to fully understand them, both must be looked beyond appearances, through a "close-up" process taken to the extreme. It is not simply a matter of focusing on details, as happens in photography and cinema fields; the intention is to delve deeper and deeper to the fuller extent: an in-depth analysis of whatever is behind, starting from the exterior to gradually shift to construction technologies, materials, up to their chemicals. The latter is, of course, not the responsibility of architects, but it lies at the heart of Life Cycle Assessment (LCA), analyses that I usually perform during the decision-making at the different process stage to help building stakeholders minimize environmental impacts across the entire – potentially multiple – life cycle. For architectural technology, for example, it is a matter of addressing, alongside conventional requirements (e.g. performance, safety, usability, well-being), the specific requirements of environmental sustainability (e.g. the rational use and optimization of materials, energy, water), taking into account the technical feasibility and evaluating the entire life cycle. At the utmost, it is to look into everything that underlies the presence of that specific material in that exact spot, its behaviour and interrelationships when in service, and its post-use journey, setting up the necessary network to actually close the loop in practice. Material-immaterial synergy: the invisible foundations of sustainable architecture To embrace this vision, the idea of resources is to be extended compared to the ordinary sense. Certainly, buildings are made and calls for a set of tangible resources, such as money to be started, bricks, steel, or timber to be erected, tools and equipment to be managed including in the long-term. The issue that often runs out is that buildings rely heavily as well on intangible resources, namely knowledge, skills, processes, organisation, information flows and network. These two dimensions – tangible and intangible – are closely connected and interdependent on each other. Without appropriate eco-design knowledge, even the best materials are wasted; without materials, knowledge has no application. In such a mindset, architecture becomes a remarkable expression of the synergy between tangible resources and intangible resources: a space where East and West can successfully meet, building a bridge across cultures through openness and inclusiveness. Indeed, it is well recognized that different traditions bring different perspectives and, when combined, generate the best and more holistic solutions. The "living building" is both a technical and cultural artefact, an expression of human creativity that must not overstep the planetary boundary. Strategic imperative: cross-border and cross-disciplinary cooperation Evidence is found in international collaborations such as Joint Schools, where universities from different countries join forces to promote shared research and training. A concrete example of Sino-foreign cooperation is the XJTU-POLIMI Joint School, opened in Xi'an (China) in 2019 through a partnership between Politecnico di Milano and Xi'an Jiaotong University. As POLIMI's first campus outside Italy, it serves as an international platform dedicated to education and research as well as technology transfer and business incubation. This initiative, like others currently in place, aims to take the best of each part to foster shared growth and mutual learning. Italy brings its strong polytechnic culture, its multidisciplinary approach and focus on design quality, together with the European emphasis on social and environmental responsibility. China, in turn, is a leader in fast-evolving business, in the integration capacity of digital technologies and in large-scale engineering projects, pulled by top-down policies that allow fast implementation. In conjunction, these strengths can create fertile ground for innovation and speed up the transformation process within the Architectural, Engineering and Construction (AEC) sector, always been acknowledged as resistant to change, due to its intrinsic complexity and fragmented nature. Rethinking the built environment: buildings as resource-driven assets The effort is to move beyond the concept of buildings as "material banks" – namely repositories where resources are temporarily stored – to rethink them and push the vision further of buildings as "resource-driven assets". While the first construct is earmarked for physical goods, that proposed calls for careful consideration of both tangible/material/visible resources and intangible/immaterial/invisible resources, taking care that everything is optimised and nothing is wasted, to preserve their value over time. In practice, this means looking at what goes into buildings, such as materials, systems and the energy required to transform and assemble them, but also, for instance, the set of expertise, skills and specialization of practitioners involved during design. Similarly, starting from the outset, it means looking at what comes out throughout buildings life, like emissions, waste, and decommissioned materials, but also knowledge gained from monitoring and lessons learned from operations. To ignore either side of the equation (inputs-outputs) would be a missed opportunity. If we want buildings to truly act as resource-driven assets, we must synergise, map, understand, and manage the full spectrum of in- and out- flows, both tangible and intangible. On the tangible side, this requires a deep understanding of material, energy and water flows across the entire life cycle. Which resources are extracted, transported, and assembled? How much energy is consumed, and how is it sourced? How do materials degrade over time, and how can they be reused or recycled without losing quality? These questions are essential to reduce impacts and to design systems that are both efficient and resilient. On the intangible side, equally important are the flows of information and knowledge that connect all actors in the construction value chain. Long before a building is erected, crucial questions are: How is data exchanged among stakeholders? Is communication efficient enough to speed up the workflows? How can design capabilities evolve into maturity, meaning quality achieved through best practice? Then, as more buildings themselves add to this immaterial layer through sensors, smart meters, and digital platforms that produce valuable insights, another set of questions follows: How is this information managed, shared, and preserved? How to ensure that data supports predictive maintenance and reverse logistics? How to activate new business models based on sharing and collaboration? Just as materials should not be wasted, neither should information. Data and knowledge must be treated as resources that enrich our collective know-how, building an "infodump bank" that not only improves current performance but also informs future decisions, guides new designs and strengthens subsequent projects. The correlation between tangible and intangible resources is ever closer: managing them together ensures that nothing is wasted and that the embedded value is preserved across time. In that respect, "no waste of resources" also means "no waste of value", since every material, every bit of data, and every piece of knowledge carries potential that, if carefully handled, can extend usefulness, inspire innovation, and create lasting benefits well beyond the life of a single project. Global impact: construction sector as global lever for planetary sustainability Through joint research and cross-border exchange programmes, the construction sector proves to be an extraordinary testing ground and given its global impact in terms of emissions and resource consumption, it clearly stands as a priority for change. Furthermore, never forget that buildings are everywhere and shape our daily lives, leading mindful planning crucial not only for preserving the natural environment but also human well-being. In this framework, architects, engineers, designers, scientists and all necessary professionals can work side by side to explore new possibilities, even creating new synergies across key business sectors. Imagine if constructions integrate materials from unexpected sources such as fashion and/or food waste. Fast-fashion clothing and textile scraps, invasive plants and agricultural by-products, or even organic waste – which are currently a significant environmental burden with serious social effects – can be rethought as valuable inputs for new building solutions. In this way, the concept of waste disappears, as it serves as input resources from another industrial sector, consequently, contributing to lower material intensity (virgin material reduction), greater industrial symbiosis (new business opportunities), and implementing smarter ways to manage resources. At the same time, digital technologies and artificial intelligence can support this process, helping to track resources, optimise flows, and potentially update in real-time the expected environmental impacts in relation to what actually happens. The ambition is to create architecture that is resource efficient and socially valuable in the long term. Considering the key role of construction, even small changes, when scale up to thousands of buildings and millions of people, can make a big difference for the planet. At this point, the key role of China is beyond question. As the world's largest construction market and major exporter, its choices strongly affect global trends, making environmental awareness and transparency in its building sector essential. Indeed, in a globalised economy, what is produced in one region may be assembled in another, used in a third and so on throughout the different stages of the life cycle, spreading responsibilities across several borders. For this reason, it is imperative to turn LCA into a standard practice, but also to regionalise results, to identify where the greatest impacts occur over the building life cycle, including in geographical terms. Here, China inevitably results in a central hotspot to concentrate efforts: improving practices there could deliver benefits worldwide, setting the chance to become an outstanding reference and reducing burdens far beyond its borders, (hopefully) without exceeding the limits of the planet. Yet – be warned – the focus is not solely on new construction, where starting from scratch makes everything easier: the real challenge (and greatest opportunity) stands in the existing building stock, because of representing the largest reserve of resources we already have. These artefacts embody vast amounts of materials, energy, and human effort that should not be wasted leaving unfinished and/or uninhabited. Instead of discarding them, we must be proactive to renew the existing buildings, extending their service life while improving performance to meet ever-evolving needs. Call to action: building bridges within planetary boundaries It is time to join forces, to move from theory to practice, from words to action. To succeed, we need lots more than technology. We need dialogue between cultures; we need young and open minds, trained to think across disciplines and borders, ready to learn from diversity, capable of working together toward a unified vision, think globally while acting locally. Green architecture should not be perceived as a trend, but as a common responsibility of the present for the future. These are just the premises to the most open question ever: "What if we built bridges between East and West, without crossing the limits of our planet?" I therefore invite everyone to begin offering practical responses, reframing global challenges as shared opportunities for innovation. Profile: Anna Dalla Valle is an Assistant Professor and Researcher in the Department of Architecture, Built Environment and Construction Engineering (DABC) at Politecnico di Milano, Italy. She is an associate and active member of both the Italian LCA Network Association and the Italian Society of Architectural Technology. She represents Politecnico di Milano in the New European Bauhaus initiative and fully participates in various international organizations, including the LCA Working Group of the Italian Green Building Council, the Italian Circular Economy Stakeholder Platform, and the International Energy Agency’s working group on ' Ways to Implement Net-zero Whole Life Carbon Buildings'. 
。 最近的理论预测表明，这些矮小的卫星星系必须受到一个无孔不入的防护罩的保护，以防止银河系将其基本的恒星形成气体移除。这种所谓的麦哲伦日冕，由温度为50万度的超强气体组成，将作为麦哲伦云周围的一种宇宙碰撞区，使圆盘和恒星在碰撞中相对不受伤害。尽管模拟显示麦哲伦日冕应该存在，但观察到的证据仍然难以找到。
二 | 利用哈勃太空望远镜和远紫外光谱探测器独特的紫外线视野，加上遥远的类星体的探测能力，天文学家终于能够探测到麦哲伦日冕并开始绘制其地图。
三 | 这个由热气体组成的弥漫性光环的发现，从大麦哲伦云延伸出10万光年，覆盖了南部天空的大部分，证实了这个预测。
四 | 它还照亮了我们对小星系如何与大星系互动而不失去未来恒星形成所需燃料的理解。距离地球近20万光年的大麦哲伦星系是银河系的一个卫星星系，它漂浮在太空中，围绕着我们的银河系跳着漫长而缓慢的舞蹈。当银河系的引力轻柔地拉扯着它邻居的气体云时，它们就会坍塌，形成新的恒星。反过来，这些恒星又将气体云照亮，呈现出万花筒般的色彩，在这张来自美国宇航局/欧空局哈勃太空望远镜的图像中可以看到。几十亿年来，大麦哲伦云和小麦哲伦云--银河系最大的卫星星系一直遵循着一个危险的旅程。当它们被拉向我们的母星系时，它们相互绕行，开始解体，留下了气态碎片的痕迹。然而，这些矮星系仍然完好无损，持续进行着旺盛的恒星形成，让天文学家们大惑不解。很多人都在努力解释这些物质流怎么可能存在，如果这些气体被从这些星系中移除，它们怎么还能形成恒星呢？由Krishnarao领导的一个天文学家小组终于找到了答案，在美国宇航局哈勃太空望远镜和一颗名为远紫外光谱探测器（FUSE）的退役卫星的数据帮助下，他们发现麦哲伦星系被一个日冕所包围，这是一个由高温超强气体组成的保护罩。这将这两个星系包裹起来，防止它们的气体供应被银河系抽走，从而使它们能够继续形成新的恒星。这一发现刚刚于9月28日发表在《自然》杂志上，涉及到星系演化的一个新方面。
五 | 马里兰州巴尔的摩太空望远镜科学研究所的共同研究者安德鲁-福克斯说："星系将自己包裹在气态的茧中，作为对其他星系的防御性盾牌。"几年前，天文学家预测了日冕的存在。"我们发现，如果我们在模拟麦哲伦云落入银河系的过程中加入日冕，我们就可以首次解释提取气体的质量，"威斯康星大学麦迪逊分校的共同研究者埃琳娜-德翁吉亚解释说。"我们知道，大麦哲伦云应该有足够大的质量来拥有一个日冕"。然而，虽然覆盖了南部天空的很大一部分，并从麦哲伦云延伸到10万光年以上，但日冕实际上是看不见的。事实上，绘制它需要从30年的存档数据中搜寻合适的测量数据。科学家们认为，星系的日冕是数十亿年前坍缩形成星系的原始气体云的残留物。尽管在更遥远的矮星系周围已经看到了日冕，但天文学家以前从未能够像这样详细地探测一个日冕。Krishnarao说："在计算机模拟中，有很多关于它们应该是什么样子的预测，它们在数十亿年中应该如何互动，但是在观测中，我们无法真正测试其中的大部分，因为矮星系通常太难探测了。因为它们就在我们家门口，麦哲伦云提供了一个研究矮星系如何互动和演变的绝佳机会。
六 | "为了寻找麦哲伦日冕的直接证据，研究小组在哈勃和FUSE档案中筛选了位于麦哲伦日冕后面数十亿光年的类星体的紫外线观测。类星体是星系中极其明亮的核心，其中含有大量活跃的黑洞。尽管科学家们推断，尽管日冕会太暗而无法单独看到，但他们认为，它应该作为一种雾气，遮蔽和吸收来自背景中类星体的明显的亮光模式。
七 | 过去，哈勃对类星体的观测被用来绘制仙女座星系周围的日冕。
八 | 通过分析来自28个类星体的紫外光模式，研究人员能够检测和描述大麦哲伦星系周围的物质，并确认日冕的存在。
九 | 正如预测的那样，类星体光谱上印有碳、氧和硅元素的明显特征，这些特征构成了环绕银河系的热等离子体光晕。
十 | 需要极其详细的紫外线光谱来探测日冕。
十一 | "哈勃和FUSE的分辨率对这项研究至关重要，Krishnarao解释说。"日冕气体是如此的弥漫，它甚至几乎不存在。此外，它还与其他气体混合在一起，包括从麦哲伦云中拉出的气流和源自银河系的物质。"通过绘制结果，研究小组还发现，气体的数量随着与大麦哲伦云中心的距离而减少。这是一个完美的提示信号，表明这个日冕真的存在，它确实在为星系形成一个保护盾。如此稀薄的气体笼罩如何能够保护一个星系免遭破坏？任何试图进入星系的东西都必须先通过这种物质，所以它可以吸收一些冲击。此外，日冕是第一个可以被提取的材料。在放弃一点日冕的同时，受保护星系本身内部的气体，能够形成新的恒星。
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