Imperial College Astrophysics Consolidated Grant 2019 - 2022

我们在天体物理学方面的研究包括宇宙学(研究宇宙)、最遥远的星系、系外行星(围绕其他恒星的行星)和引力波(爱因斯坦预测的时空扭曲，最近首次观测到)。这项工作将有助于回答人们可能提出的一些最伟大的问题，包括：我们能否在太阳系外找到生命的迹象？宇宙的命运又是什么呢？我们的工作包括理论、观察和实验室工作的结合。我们使用了尖端的设施，如普朗克和赫歇尔卫星，以及未来的欧几里德卫星、平方公里阵列和大型天气观测望远镜。我们还发展了理论，这将导致对下一代卫星和实验的发展提出建议。此外，我们还在实验室中测量不同原子的基本性质，以便与恒星中不同元素的观测进行比较。在过去的20年里，我们对宇宙本质的理解发生了深刻的变化，因为我们发现宇宙的膨胀正在加速，而作为实验，主要是观察宇宙微波背景的实验，使得描述宇宙的参数-普通物质(原子)、暗物质和暗能量的比例以及当前的膨胀速度-得以准确测量。暗物质在引力作用下聚集，重量比普通物质大5倍，但它的组成尚不清楚。更大的谜团是暗能量，它导致了宇宙的加速，并主导着质量能量预算。我们在宇宙学方面的工作采取了不同的方法来回答这些问题。但我们研究的共同主题是认识到，进步将通过更准确地测量数量(宇宙距离、膨胀率)的改进实验来实现。这些实验依赖于更好的技术(例如，测量宇宙微波背景的偏振)，更好地理解正在研究的物理(用于测量宇宙距离的超新星的性质)，以及更好的数据分析技术，以提高结果的精确度和准确性。对人类来说，同样意义深远的是，在过去20年里，发现了围绕我们银河系中许多最近恒星的行星，并首次描述了其他恒星系统的特征。如果最终目标是发现其他行星上的生命，这将通过以下方面的不断进步来实现：理解不同类型的行星(岩石/气体、大/小)是如何在不同的径向分离的不同类型的恒星(老/年轻、活跃/不活跃、热/冷)的周围形成的，以及恒星在其一生中如何影响其行星上的条件。我们在这一领域的工作包括理论工作，以了解行星形成的机制，以及对恒星的可变性以及这如何微妙地影响行星大气的测量(可能导致错误结论)的更深层次的理解。爱因斯坦1915年的广义相对论描述了由于质量导致的时空曲率，其结果是，正在加速的大质量物体以引力波的形式辐射能量，以光速传播。经过几十年的开发工作，为了提高仪器的灵敏度，引力波终于在2015年9月被先进的LIGO财团探测到。这一发现开启了一种全新的探索宇宙的方式，提供了丰富的新可能性。我们对这一领域的兴趣是超前思考，通过发展什么可能被检测到的理论，预测如何解释新的测量结果，并指导下一代仪器的发展。

Our research in Astrophysics includes the areas of cosmology (thestudy of the Universe), the most distant galaxies, exoplanets (planetsaround other stars), and gravitational waves (distortion of space-timepredicted by Einstein, and recently observed for the first time). Thiswork will make a contribution towards answering some of the greatestquestions that can be posed, including: can we find signs of lifeoutside the solar system? and what is the fate of the Universe? Ourwork involves a combination of theory, observations, and laboratory work. We usecutting-edge facilities such as the Planck and Herschel satellites,and in the future the Euclid satellite, the Square Kilometre Array,and the Large Synoptic Survey Telescope. We also develop thetheory that will lead to proposals for the development of the nextgeneration of satellites and experiments. In addition we measure inthe laboratory fundamental properties of different atoms, forcomparison against observations of the different elements in stars.Our understanding of the nature of the Universe has changed profoundlyover the past 20 years, since it was discovered that the expansion ofthe Universe is accelerating, and as experiments, primarily thoseobserving the cosmic microwave background, have allowed the accuratemeasurement of the parameters describing the Universe - theproportions of ordinary matter (atoms), dark matter, and dark energy,and the current rate of expansion. Dark matter clumps gravitationallyand outweighs ordinary matter by a factor 5, but what it consists ofis unknown. The even greater mystery is dark energy, which is causingthe acceleration of the Universe, and which dominates the mass-energybudget. Our work in cosmology takes different approaches to answeringthese problems. But the common theme in our research is theunderstanding that advances will come through improved experimentsthat measure quantities (cosmological distances, the rate ofexpansion) more accurately. The experiments rely on better technology(e.g. measurements of polarisation of the cosmic microwavebackground), better understanding of the physics under study (theproperties of supernovae used to measure cosmological distances), andbetter data analysis techniques that improve the precision andaccuracy of the results.No less profound for humankind has been the discovery, again over thepast 20 years, of planets around many of the nearest stars in ourgalaxy, and the first characterisation of other stellar systems. Ifthe ultimate goal is to discover life on other planets this will beachieved through successive advances in understanding how differenttypes of planet (rocky/gaseous, large/small) form around differenttypes of star (old/young, active/inactive, hot/cool) at differentradial separations, and of how the star over its lifetime can affectthe conditions on its planets. Our work in this area includestheoretical work to understand the mechanisms by which planets form,as well as developing a deeper understanding of stellar variabilityand how this can subtly bias measurements of the atmospheres ofplanets (possibly leading to erroneous conclusions).A consequence of Einstein's 1915 theory of general relativity, whichdescribes the curvature of space-time due to mass, is that massiveobjects undergoing acceleration radiate energy in the form ofgravitational waves, propagatingat the speed of light. After decades of development work, toimprove the sensitivity of the instruments, gravitational waves werefinally detected in September 2015 by the Advanced LIGO consortium.This discovery opens up an entirely new way of exploring the universe,offering rich new possibilities. Our interest in this field is inthinking ahead, by developing the theory of what might be detectable,to anticipate how to interpret new measurements, and to guide thedevelopment of the next generation of instruments.