Gas, dust and stars: the life cycle of galaxies

宇宙在不断地演化。恒星是由气体云形成的。它们通过将氢燃烧成氦，然后再燃烧成碳和氧来生存。核燃烧发生在恒星的中心，但产物被带到表面，改变了恒星的组成。在生命的尽头，恒星会在一场灾难性的风中排出一半或更多的质量。从这些进化的恒星中喷出的物质形成了奇妙而美丽的结构（例如行星状星云），我们并不完全了解产生这些结构的物理原理，但怀疑双星系统和磁场是一个因素。风将新形成的元素驱逐到太空中，在那里它们丰富了气体云。因此，下一代恒星将受益于这些新元素。同时，一些元素凝结成小颗粒，形成尘粒。这些颗粒也被添加到云中。当新的恒星从这个云团中形成时，一些尘埃将开始形成行星。我们正在研究恒星、尘埃和气体的演化周期。我们研究了新尘埃进入星际介质的情况，观察了各种各样的物体，特别强调了早期宇宙中存在的低金属丰度条件。我们研究恒星是如何形成的，尤其是比太阳质量大的恒星。我们观察一个完整星系（大麦哲伦星云是主要目标）上尘埃的特性。我们也研究星际和星周气体的化学性质。我们还试图了解双星系统的存在如何影响质量损失过程的物理性质。太阳系本身就是宇宙进化的结果。它形成时留下的尘埃仍然存在，形成大颗粒甚至彗星和陨石。宇宙飞船正在收集这些尘埃。我们研究的目标之一是在其他恒星的流出物中找到原始太阳尘埃的后代。

The Universe is in constant evolution. Stars form out of clouds of gas. They live by burning hydrogen into helium, and later into carbon and oxygen. The nuclear burning takes place in the centre of the stars, but the products are brought to the surface and change the composition of the star. At the end of its life, the star will expel half or more of its mass in a catastrophic wind. The material blown off from these evolved stars forms fantastic and beautiful structures (e.g. Planetary Nebulae), we don't fully understand the physics that generates the structures but suspect that binary systems and magnetic fields are a factor. The wind expels the newly formed elements into space where they enrich clouds of gas. Thus, the next generation of stars will benefit from these new elements. At the same time, some elements condense as small particles, forming dust grains. These grains are also added to the clouds. When new stars form from this cloud, some of this dust will start the formation of planets. We are studying this cycle of evolution of stars, dust and gas. We study the input of new dust into the interstellar medium, looking at a variety of objects, with special emphasis on conditions of low metallicity, as existed in the early Universe. We study how stars form, especially stars more massive than the Sun. We look at the properties of dust over a complete galaxy (the Large Magelanic Cloud is the main target). We also study the chemistry of interstellar and circumstellar gas. We are also trying to understand how the presence of binary systems can affect the physics of the mass-loss process. The solar system is itself the result of this Universe of evolution. Dust left over from its formation is still present, incorporated in large grains or even comets and meteorites. Space craft are now collecting this dust. One of the goals of our research is to find the progeny of the proto-solar dust, among the outflows of other stars.