This paper is an introduction to volume 56 of the Space Science Series of ISSI, “From disks to planets—the making of planets and their proto-atmospheres”, a key subject in our quest for the origins and evolutionary paths of planets, and for the causes of their diversity. Indeed, as exoplanet discoveries progressively accumulated and their characterization made spectacular progress, it became evident that the diversity of observed exoplanets can in no way be reduced to the two classes of planets that we are used to identify in the solar system, namely terrestrial planets and gas or ice giants: the exoplanet reality is just much broader. This fact is no doubt the result of the exceptional diversity of the evolutionary paths linking planetary systems as a whole as well as individual exoplanets and their proto-atmospheres to their parent circumstellar disks: this diversity and its causes are exactly what this paper explores. For each of the main phases of the formation and evolution of planetary systems and of individual planets, we summarize what we believe we understand and what are the important open questions needing further in-depth examination, and offer some suggestions on ways towards solutions.We start with the formation mechanisms of circumstellar disks, with their gas and disk components in which chemical composition plays a very important role in planet formation. We summarize how dust accretion within the disk generates planet cores, while gas accretion on these cores can lead to the diversity of their fluid envelopes. The temporal evolution of the parent disk itself, and its final dissipation, put strong constraints on how and how far planetary formation can proceed. The radiation output of the central star also plays an important role in this whole story. This early phase of planet evolution, from disk formation to dissipation, is characterized by a co-evolution of the disk and its daughter planets. During this co-evolution, planets and their protoatmospheres not only grow, but they also migrate radially as a result of their interaction with the disk, thus moving progressively from their distance of formation to their final location. The formation of planetary fluid envelopes (proto-atmospheres and oceans), is an essential product of this planet formation scenario which strongly constrains their possible evolution towards habitability. We discuss the effects of the initial conditions in the disk, of the location, size and mass of the planetary core, of the disk lifetime and of the radiation output and activity of the central star, on the formation of these envelopes and on their relative extensions with respect to the planet core. Overall, a fraction of the planets retain the primary proto-atmosphere they initially accreted from the gas disk. For those which lose it in this early evolution, outgassing of volatiles from the planetary core and mantle, together with some contributions of volatiles from colliding bodies, give them a chance to form a “secondary” atmosphere, like that of our own Earth.When the disk finally dissipates, usually before 10 Million years of age, it leaves us with the combination of a planetary system and a debris disk, each with a specific radial distribution with respect to their parent star(s). Whereas the dynamics of protoplanetary disks is dominated by gas-solid dynamical coupling, debris disks are dominated by gravitational dynamics acting on diverse families of planetesimals. Solid-body collisions between them and giant impacts on young planetary surfaces generate a new population of gas and dust in those disks. Synergies between solar system and exoplanet studies are particularly fruitful and need to be stimulated even more, because they give access to different and complementary components of debris disks: whereas the different families of planetesimals can be extensively studied in the solar system, they remain unobserved in exoplanet systems. But, in those systems, long-wavelength telescopic observations of dust provide a wealth of indirect information about the unobserved population of planetesimals. Promising progress is being currently made to observe the gas component as well, using millimetre and sub-millimetre giant radio interferometers.Within planetary systems themselves, individual planets are the assembly of a solid body and a fluid envelope, including their planetary atmosphere when there is one. Their characteristics range from terrestrial planets through sub-Neptunes and Neptunes and to gas giants, each type covering most of the orbital distances probed by present-day techniques. With the continuous progress in detection and characterization techniques and the advent of major providers of new data like the Kepler mission, the architecture of these planetary systems can be studied more and more accurately in a statistically meaningful sense and compared to the one of our own solar system, which does not appear to be an exceptional case. Finally, our understanding of exoplanets atmospheres has made spectacular advances recently using the occultation spectroscopy techniques implemented on the currently operating space and ground-based observing facilities.The powerful new observing facilities planned for the near and more distant future will make it possible to address many of the most challenging current questions of the science of exoplanets and their systems. There is little doubt that, using this new generation of facilities, we will be able to reconstruct more and more accurately the complex evolutionary paths which link stellar genesis to the possible emergence of habitable worlds.

中文翻译：

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从磁盘到行星：行星的形成及其早期大气。一个介绍

这篇论文是对 ISSI 空间科学系列第 56 卷“从磁盘到行星——行星及其原始大气层的形成”的介绍，这是我们探索行星起源和演化路径的关键主题，以及其多样性的原因。事实上，随着系外行星发现的逐渐积累和它们的表征取得了惊人的进展，很明显，观测到的系外行星的多样性绝不能归结为我们习惯于在太阳系中识别的两类行星，即类地行星和类地行星。气体或冰巨人：系外行星的现实范围要广泛得多。这一事实无疑是将行星系统作为一个整体以及单个系外行星及其原始大气与其母星周盘联系起来的进化路径异常多样性的结果：这种多样性及其原因正是本文所探讨的。对于行星系统和单个行星形成和演化的每个主要阶段，我们总结了我们认为自己理解的内容以及需要进一步深入研究的重要开放性问题，并提供了一些解决方法的建议。从星周盘的形成机制开始，从它们的气体和盘成分开始，其中化学成分在行星形成中起着非常重要的作用。我们总结了盘内的尘埃吸积如何产生行星核心，而这些岩心上的气体吸积会导致其流体包层的多样性。母盘本身的时间演化及其最终消散，对行星形成的方式和距离施加了强烈的限制。中央恒星的辐射输出在整个故事中也起着重要作用。行星演化的早期阶段，从盘形成到消散，其特征是盘及其子行星的共同演化。在这种共同演化过程中，行星及其原始大气层不仅在生长，而且由于它们与圆盘的相互作用，它们还会径向迁移，从而从它们的形成距离逐渐移动到它们的最终位置。行星流体包层（原始大气和海洋）的形成，是这种行星形成场景的重要产物，它强烈限制了它们可能向宜居性的进化。我们讨论了圆盘中的初始条件、行星核心的位置、大小和质量、圆盘寿命以及中心恒星的辐射输出和活动、这些包层的形成及其相对的影响。相对于行星核心的扩展。总体而言，一小部分行星保留了它们最初从气盘吸积的主要原始大气层。对于那些在早期演化中失去它的人来说，行星核心和地幔中挥发物的脱气，以及来自碰撞天体的挥发物的一些贡献，使它们有机会形成“二次”大气，就像我们自己的地球一样。磁盘终于消散，通常在 1000 万年之前，它给我们留下了一个行星系统和一个碎片盘的组合，每个都具有相对于它们的母星的特定径向分布。原行星盘的动力学受气固动力学耦合支配，而碎片盘受作用于不同类星子的引力动力学支配。它们之间的固体碰撞以及对年轻行星表面的巨大撞击在这些圆盘中产生了新的气体和尘埃群。太阳系和系外行星研究之间的协同作用特别富有成效，需要进一步激发，因为它们可以访问碎片盘的不同和互补成分：而在太阳系中可以广泛研究不同的星子家族，它们在系外行星系统中仍未被观察到。但是，在这些系统中，对尘埃的长波长望远镜观测提供了大量关于未观察到的星子种群的间接信息。目前正在使用毫米和亚毫米巨型无线电干涉仪观测气体成分方面取得了可喜的进展。在行星系统本身中，单个行星是固体和流体包层的组合，包括它们的行星大气一。它们的特征范围从类地行星到亚海王星和海王星，再到气态巨行星，每种类型都涵盖了当今技术探测到的大部分轨道距离。随着检测和表征技术的不断进步以及像开普勒任务这样的新数据主要提供者的出现，这些行星系统的结构可以在统计意义上越来越准确地进行研究，并与我们自己的太阳系进行比较，这似乎不是一个例外。最后，我们对系外行星大气层的理解最近取得了惊人的进展，使用了在当前运行的空间和地基观测设施上实施的掩星光谱技术。为近期和更远的未来计划的强大的新观测设施将使解决许多问题成为可能。系外行星及其系统科学中最具挑战性的当前问题之一。毫无疑问，使用这种新一代设施，