The Planet-Disk Connection: Accretion, Disk Structure, and Planet Formation

“恒星和行星系统是如何发展的，生命是我们星球的专属吗？“是人类面临的重大问题之一，也是STFC提出的科学挑战之一。在邓迪，我们是一个小，但年轻和充满活力的部门，在理解恒星和行星的形成的强烈关注，该集团正在苏格兰大学物理联盟（SUPA）和圣安德鲁斯系外行星中心的大背景下增长。我们的主要目标是探索行星形成环境的观测和计算。行星诞生于围绕年轻恒星形成的原行星盘中，由气体和尘埃组成，大小从非常小的颗粒到鹅卵石。我们使用多望远镜，多波长数据和最先进的计算机模拟来跟踪恒星与原行星盘的形成，跟踪磁盘的演变，因为它们分散，并研究行星系统如何形成和演变出一个消散的磁盘。观测研究正在进行的行星盘形成的主要问题之一是，最里面的部分（包括可居住区，液态水可以使行星成为生命的区域）太小，太暗，即使是最强大的现有干涉仪也无法直接解决。我们的项目将开发特殊的观测技术，以探索年轻恒星周围的条件和靠近中心恒星的最里面的行星形成区域，在那里现在发现了许多行星。由于对盘的观测提供了盘演化的快照，而观测到的系外行星显示了行星形成的结束状态，因此我们还旨在通过使用计算机模拟来连接行星形成的开始和结束（即盘和行星），并将模拟与观测到的盘和系外行星进行比较。第一个关键是探索速度和时间维度，以跟踪微小的空间结构：利用多普勒效应和随时间的重复观测，我们可以跟踪圆盘材料的轨道，螺旋和吸积到中心星星上，映射在几个恒星半径的最里面的区域，并确定整个圆盘的物质流动。这两个量对于探索星星在未来是否足够安静以允许可居住的行星，以及物质在行星形成区通过圆盘的方式都非常重要。它还将使我们能够区分观测到的行星特征与吸积和活动特征，从而促进未来对非常年轻的行星的探测。第二个关键是“Rosseta Stone”技术，使用各种望远镜在许多不同的波长（颜色）进行观测。类似于原始罗塞塔石碑的不同语言，每个波长都以略微不同的方式告诉我们磁盘的各个方面。通过将它们结合起来用于大量的物体，我们可以获得原行星盘的全球性质的准确图像，并探索行星形成的特征。第三个关键是使用计算机模拟，通过探索数百万年时间尺度上行星的形成，弥合原行星盘和系外行星系统之间的差距。我们将从我们对大量圆盘的多波长观测中构建一个现实的圆盘模型，并将其用作行星形成模拟的起点。然后，我们将比较模拟行星系统的性质与观测到的行星系统的性质，这也将有助于我们排除或确认无法直接观测到的盘性质和物理过程。我们的目标是通过揭示它们起源于哪种盘来了解已知的各种行星，并通过探索行星形成对盘演化的影响来了解所观察到的各种原行星盘。

"How do stars and planetary systems develop and is life exclusive to our planet?" is one of the major questions of humanity, and also one of the Science Challenges proposed by the STFC. In Dundee, we are a small but young and vibrant department with a strong focus in understanding the formation of stars and planets, and the group is growing within the larger context of the Scottish Universities Physics Alliance (SUPA) and the St Andrews Exoplanet Centre.Our main objective is to explore planet formation environments both observationally and computationally. Planets are born in protoplanetary disks formed around young stars, composed of gas and dust with sizes from very small particles to pebbles. We use multi-telescope, multi-wavelength data and a state-of-the-art computer simulations to track the formation of stars together with protoplanetary disks, to follow the evolution of disks as they disperse, and to study how planetary systems form and evolve out of a dissipating disk. One of the main problems of observationally studying the ongoing planet formation in disks is that the innermost part (which includes the habitable zone, the region where liquid water could enable planets to host life) is too small and too faint to be directly resolved even by the most powerful existing interferometers. Our project will develop special observational techniques to explore the conditions around young stars and in the innermost planet formation regions near the central stars, where many planets are now being discovered. Since observations of disks provide snapshots of disk evolution while observed exoplanets show the end state of planet formation, we also aim to connect the beginning and the end of planet formation (i.e. disks and planets) by using computer simulations, and will compare simulations with both observed disks and exoplanets. The first key is to explore the velocity and time dimension to track tiny spatial structures: using the Doppler effect and repeated observations over time, we can track the disk material as it orbits, spirals and accretes onto the central star, mapping the innermost regions at few stellar radii and determining the flow of matter throughout the disk. Both quantities are very important to explore whether the star will be quiescent enough in the future to allow for habitable planets, and the way matter moves through the disk in the planet-forming zone. It will also enable us to distinguish observational planetary signatures from those of accretion and activity and thus facilitate the detection of very young planets in the future. The second key is the "Rosseta Stone" technique, using observations at many different wavelengths (colours), taken with various telescopes. Similar to the different languages of the original Rosetta Stone, each wavelength tells us about aspects of the disk in a slightly different way. By combining them all for large numbers of objects, we can obtain an accurate picture of the global properties of protoplanetary disks and explore the signatures of planet formation. The third key is to use computer simulations to bridge the gap between protoplanetary disks and exoplanetary systems by exploring the formation of planets over a few million year timescale. We will construct a realistic disk model from our multi-wavelength observations for a large number of disks and use that as the starting point of planet formation simulations. We will then compare the properties of the simulated planetary systems with those of observed ones, which will also help us to rule out or confirm disk properties and physical processes that are not directly observable. Our goals are to put into context the known variety of planets by revealing from which kinds of disks they have originated, and to understand the observed variety of protoplanetary disks by exploring the effect of planet formation on the evolution of the disk.