Astrophysics at St.Andrews

我们的银河系包含许多其形成历史的化石。很久以前与银河系相撞的较小星系形成了恒星流，这些恒星流仍然作为银河系形成的化石而存在，在银河系原始暗物质晕的引力场中绕轨道运行。从2011年起，GAIA使命将绘制这些流的位置和运动。我们将开发新的技术，利用来自GAIA的数据来绘制暗物质，并测试传统的引力理论在大距离下是否如预期的那样工作。在描绘银河系旋臂的气体和尘埃的黑暗云团中，新的恒星和行星系统不断形成。在最大的星团中，恒星的质量是太阳的100倍。这些大质量恒星燃烧得如此明亮，以至于在邻近的星系中清晰可见。其中许多是双星。我们对它们的相互食和光谱的测量将揭示它们的大小和温度，从而揭示它们到最近星系的距离。我们还不知道这些大质量恒星是如何形成的，也不知道为什么它们中有这么多是双星。我们将模拟最大质量和最热的恒星是如何形成的，尽管它们的辐射场倾向于吹走供给它们的气体。我们还想弄清楚它们的风，以及最终将它们吹散的超新星爆炸产生的冲击波，是如何影响邻近的气体云的，也许会引发新的星星形成的爆发。恒星形成的暗云包含针状尘埃颗粒，这些尘埃颗粒与银河系的磁场和穿过它们的电磁辐射排成一行。我们将测量来自星云物质刚刚开始形成新恒星的区域的红外和毫米波辐射的偏振，以发现当星星凝聚时磁场和颗粒本身发生了什么。新生的恒星被扁平的、旋转的气体和尘埃盘所包围，这些气体和尘埃盘持续存在两三百万年。当行星在盘状物质中形成时，一些气体继续供给成长中的星星，在这个阶段，恒星具有很强的磁场。我们现在可以用新仪器绘制这些恒星的磁场。我们将使用这些地图来预测磁场如何将物质引导到流中，以及场结构如何调节流向星星的流速和星星的自旋。我们将在太阳附近寻找快速旋转的年轻恒星，这些恒星是在5000万年前形成但解体的星星团的残余物中。到了这个年龄，圆盘已经消失了，但早期过程的神秘化石残留在它们的旋转速度中。在同一个星团中其他方面相同的恒星中，有些恒星的自转速度比其他恒星快得多。我们想知道这种自转速率的差异是否是多少恒星拥有行星系统的线索，或者这种差异是否源于恒星磁场的某些特性。我们将绘制快速旋转体和它们旋转较慢的兄弟体的磁场图，看看热气体沿着沿着磁力线流出的速率是否有差异，可以带走星星的自旋。最后，我们将寻找附近和遥远恒星周围的行星系统。我们正在与其他几个机构的天文学家合作，监测附近数十万颗恒星的亮度，以便找出由近轨道行星大小的行星在其母星前面经过引起的微小光线下降。我们的目标是发现数十颗这样的行星，并测量它们的大小，质量和温度。我们还将通过监测遥远的恒星来寻找距离恒星更远的行星，这些恒星的光线被前景星星的引力场暂时放大。由此产生的光变化的扭曲已经揭示了这些前景恒星中的几颗周围的行星质量。我们的目标是使用一个新的机器人望远镜网络来发现更多。

Our Galaxy contains many fossils of its formation history. Smaller galaxies that collided with the Milky Way long ago formed streams of stars that still linger as fossils of the Galaxy's formation, orbiting in the gravitational field of the Galaxy's primordial dark-matter halo. From 2011 the GAIA mission will map the positions and motions of these streams. We will develop new techniques to use data from GAIA to map the dark matter, and to test whether conventional theories of gravity work as expected at large distances. Clusters of new stars and planetary systems are constantly forming inside the dark clouds of gas and dust that delineate the Milky Way's spiral arms. In the biggest clusters, stars form that are up to 100 times as massive as the Sun. These massive stars burn so brightly that they are clearly visible in neighbouring galaxies. Many of them are binary stars. Our measurements of their mutual eclipses and spectra will reveal their sizes and temperatures, and hence the distances to the nearest galaxies. We do not yet understand how these massive stars form, or why so many of them are binaries. We will simulate how the most massive and hottest stars manage to form despite the tendency of their radiation fields to blow away the gas that feeds them. We also aim to find out how their winds, and the shock waves from the supernova explosions that eventually blow them apart, affect neighbouring gas clouds, perhaps triggering new bursts of star formation. The dark clouds where stars form contain needle-like dust grains that line up with the Galaxy's magnetic fields and polarize radiation passing through them. We will measure the polarization of infrared and mm-wave radiation coming from regions where cloud material is just beginning to form new stars, to discover what is happening to the magnetic field and to the grains themselves as the star condenses. Newly-born stars are surrounded by flat, rotating discs of gas and dust, which persist for two or three million years. As planets form in the disc material, some gas continues to feed the growing star, which at this stage possesses a strong magnetic field. We can now map these stars' magnetic fields using new instruments. We will use these maps to predict how the magnetic field acts to channel material into streams, and how the field structure regulates the flow rate on to the star and the star's spin. We will seek out rapidly rotating young stars near the Sun, in remnants of star clusters that formed up to 50 million years ago but fell apart. By this age the discs have gone, but an enigmatic fossil remnant of earlier processes lingers in their spin rates. Among otherwise identical stars in the same cluster, some spin much faster than others. We want to know if this difference in spin rate is a clue as to how many stars possess planetary systems, or if the difference originates in some peculiarity of the stars' magnetic fields. We will map the magnetic fields of the fast rotators and their more slowly-rotating siblings, to see if there is a difference in the rate at which hot gas flowing out along the field lines can carry away the star's spin. Finally, we will seek out planetary systems around nearby and distant stars. We are working with astronomers at several other institutions to monitor the brightnesses of hundreds of thousands of nearby stars, in order to pick out tiny dips in light caused by close-orbiting Jupiter-sized planets passing in front of their parent stars. We aim to discover dozens of such planets, and to measure their sizes, masses and temperatures. We will also search for planets further from their stars, by monitoring distant stars whose light is being temporarily magnified by the gravitational field of a foreground star. Distortions in the resulting light variation have already revealed Jupiter-mass planets around a couple of these foreground stars. We aim to find many more using a network of new robotic telescopes.