Galactic Astronomy at the University of Hertfordshire

银河系是我们的家星系。它伴随着较小的卫星星系，最重要的是大麦哲伦云和小麦哲伦云。星系的演化与其所包含的恒星的演化密切相关。星系中以气体形式存在的物质是形成恒星和行星系统的原料。我们的小组研究了100多亿年前在银河系中诞生的第一批恒星——这个阶段现在只能在非常遥远的高红移星系中直接观察到。为了了解年轻的银河系是什么样子，我们研究了白矮星，它们是早期非常微弱的恒星残骸。一些白矮星位于双星中，它们被认为是引力波的重要来源，其中一些最终会合并并爆炸为超新星（恒星反馈到星际物质的化学和动力学的另一种途径）。为了解决恒星如何老化成为这些恒星残骸的问题，我们的小组研究了在银河系和麦哲伦星云中经历之前极端红巨星进化阶段的恒星——这是恒星在强超风阶段将物质返回星际气体的时刻。在恒星内部进行的核聚变使返回的气体在化学上富集，并将被再循环形成下一代恒星。银河系和它的卫星是我们近距离观察这些过程的唯一机会。长波观测（在亚毫米波段和红外线波段）使我们能够研究恒星和褐矮星的诞生。我们正在领导对银河系的新一代调查，旨在研究恒星的形成，从它们最初在重力作用下凝结到巨大的冷气体云，再到它们在核聚变反应的推动下成为恒星。新的调查将探测到数百个恒星正在形成的区域，包括大的星团和孤立的区域。有了这个庞大的数据集，我们可以用统计方法来确定恒星在整个银河系中形成的不同方式，以及这个过程中涉及的时间尺度。我们对附近的恒星进行系统的径向速度搜索，以发现行星，然后用高分辨率成像和光谱学跟踪其中一些，以辨别它们的大气特性。我们特别以低质量恒星为目标，通过多普勒摆动和寻找周期性地使其母星黯然失色的行星。在拨款期间，我们期望在最近恒星的可居住区域首次探测到地球质量的行星。此外，我们正在确定附近年轻的M星群，我们将用现有的和新的高分辨率设备来瞄准这些恒星，以开辟直接成像其他太阳系细节的潜力，这些太阳系的距离小到地球到太阳的距离。我们还发现，跟踪和模拟最冷的失败恒星（褐矮星）的特性，这些恒星的温度和特性与太阳系行星有很大的重叠，并能洞察围绕其他恒星运行的轨道上的行星以及它们自己的行星。

The Milky Way is our home galaxy. It is accompanied by smaller satellite galaxies, the most important ones are the Large and Small Magellanic Clouds. The evolution of galaxies is closely linked to the evolution of the stars they contain. The matter in galaxies in the form of gas is the raw material for the formation of stars and planetary systems. Our group investigates the first stars born in the Milky Way over 10 billion years ago - a phase only directly observable now in very distant galaxies at high redshift. Also with a view to understanding what the young Milky Way was like, we study stars known as white dwarfs that are the extremely faint stellar remnants from these early days. Some white dwarfs reside in binaries, which are expected to be important sources of gravitational waves, and a few of them will eventually merge and explode as supernovae (another path way by which stars feed back into the chemistry and dynamics of interstellar matter). To solve problems in how stars age to become these stellar remnants, our group investigates stars passing through the preceding extreme red giant evolutionary phase, both in the Milky Way and the Magellanic Clouds -- this is the moment when stars return matter to the interstellar gas during a strong superwind phase. The returned gas is chemically enriched by nuclear fusion that has gone on inside the stars and will be re-cycled to form the next generation of stars. The Milky Way and its satellites are our only chance to have a close-up look at these processes. Long wavelength observations (made in the sub-mm and infrared) allow us to investigate the birth of stars and brown dwarfs. We are leading a new generation of surveys of our Milky Way Galaxy that are to designed to study the formation of stars from their initial condensation under gravity from vast clouds of cold gas to their emergence as stars powered by nuclear fusion reactions. The new surveys will detect hundreds of regions where stars are being formed, both in large clusters and in isolation. With this large dataset we can use a statistical approach to determine the different ways that stars can form in the Galaxy as a whole and the timescales involved in the process. We perform systematic radial velocity searches of nearby stars to discover planets and then follow some of these up with high resolution imaging and spectroscopy in order to discern their atmospheric properties. We especially target low mass stars both using Doppler Wobble and by looking for planets periodically eclipsing their parent star. During the period of the grant we expect to make the first detections of Earth-mass planets in the habitable zones of the closest stars. In addition we are identifying populations of nearby youthful M stars which we will target with existing and new high resolution facilities to open up potential to directly image the details of other Solar Systems at separations as small as that of the Earth to Sun distance. We also discover, follow-up and model the properties of the coolest failed stars (brown dwarfs) whose temperatures and properties offer substantial overlap with Solar System planets and insight into planets in orbit around other stars as well as on their own.