About 20 years after the discovery of the first extrasolar planet, the number of planets known has grown by three orders of magnitude, and continues to increase at neck breaking pace. For most of these planets we have little information, except for the fact that they exist and possess an address in our Galaxy. For about one third of them, we know how much they weigh, their size and their orbital parameters. For less than 20, we start to have some clues about their atmospheric temperature and composition. How do we make progress from here?We are still far from the completion of a hypothetical Hertzsprung–Russell diagram for planets comparable to what we have for stars, and today we do not even know whether such classification will ever be possible or even meaningful for planetary objects. But one thing is clear: planetary parameters such as mass, radius and temperature alone do not explain the diversity revealed by current observations. The chemical composition of these planets is needed to trace back their formation history and evolution, as happened for the planets in our Solar System. As in situ measurements are and will remain off-limits for exoplanets, to study their chemical composition we will have to rely on remote sensing spectroscopic observations of their gaseous envelopes.In this paper, we critically review the key achievements accomplished in the study of exoplanet atmospheres in the past ten years. We discuss possible hurdles and the way to overcome those. Finally, we review the prospects for the future. The knowledge and the experience gained with the planets in our solar system will guide our journey among those faraway worlds.

中文翻译：

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我们银河系中行星大气的光谱

在发现第一颗系外行星大约 20 年后，已知行星的数量增加了三个数量级，并继续以惊人的速度增加。对于这些行星中的大多数，我们几乎没有信息，除了它们在我们的银河系中存在并拥有地址的事实。对于其中大约三分之一，我们知道它们的重量、大小和轨道参数。对于不到 20 个，我们开始对它们的大气温度和成分有了一些线索。我们如何从这里取得进展？ 我们离完成一个假设的赫兹-罗素行星图与我们的恒星相当，今天我们甚至不知道这样的分类是否可能甚至有意义行星物体。但有一件事是清楚的：行星参数，例如质量，仅凭半径和温度并不能解释当前观测所揭示的多样性。需要这些行星的化学成分来追溯它们的形成历史和演化，就像我们太阳系中的行星一样。由于原位测量对于系外行星来说仍然是禁区，为了研究它们的化学成分，我们将不得不依靠对其气体包层的遥感光谱观测。在本文中，我们批判性地回顾了系外行星研究中取得的主要成就过去十年的气氛。我们讨论可能的障碍以及克服这些障碍的方法。最后，我们回顾一下未来的前景。在我们太阳系中的行星上获得的知识和经验将指导我们在那些遥远的世界中的旅程。