INNATE Investigating the nature and origins of exoplanets in the Neptunian desert

自从25年前发现51peg b以来，我们对系外行星的认识发生了巨大的变化。行星现在很普遍，大多数恒星都被发现有行星系统。在已知的4300多颗行星中，可以看到分布的趋势和差距，包括行星的大小、组成和主星的性质，这些都是由塑造这些世界的形成和演化过程引起的。行星分布的一个显著特征是“海王星沙漠”，缺乏类似海王星的行星绕着它们的主星运行。离恒星很近的行星要么被蒸发掉，要么被恒星的强大引力完全破坏。然而，最近在沙漠中发现了许多行星，出乎人们的意料，也凸显了我们认识上的差距。这些热海王星的起源是未知的，它们为研究行星形成的极端结果提供了一个独特的机会。这些正常过程的异常值使我们能够以行星形成理论为基准，剥离了许多典型的简并。有了这个提议，我们将结合TESS、NGTS、CORALIE、HARPS和Gaia的光度和光谱观测，开展一项雄心勃勃的全面研究计划，调查沙漠中行星的性质和起源。(1)揭示荒漠行星的无偏统计学性质，发现行星质量、半径、密度、内部结构和主星性质的分布。(2)我们将通过确定外部伴星的存在和恒星的局部密度来建立这些系统的动力学背景。(3)我们将把测量的人口统计学、动力学和内部结构与更广泛的形成和演化理论联系起来。综合的结果不仅会改变我们对沙漠行星的理解，还会改变我们对行星系统形成、结构和演化的更广泛的理解。

Our knowledge of exoplanets has undergone a step change since the discovery of 51 Peg b 25 years ago. Planets are now commonplace, with most stars found to be hosting planetary systems. In the set of over 4300 planets known, trends and gaps in the distribution are seen with respect to planet size, composition and host star properties, arising from the formation and evolution processes which sculpt these worlds.A striking signature in the planet distribution is the 'Neptunian desert', a dearth of Neptune-like planets orbiting close to their host stars. Planets which arrive so close to their stars are evaporated away, or are disrupted entirely by the strong gravitational forces of the star. Yet, recently a number of planets have been discovered inside the desert, surprising expectations and highlighting a gap in our understanding. The origin of these hot Neptunes is unknown, and they present a unique opportunity to study the extreme outcomes of planet formation. Such outliers of the normal processes allow us to benchmark planetary formation theories, with many of the typical degeneracies stripped away.With this proposal, we will combine photometric and spectroscopic observations from TESS, NGTS, CORALIE, HARPS and Gaia to carry out an ambitious and comprehensive research program investigating the nature and origins of planets in the desert. (1) We will uncover the unbiased demographic properties of the in-desert planets, finding the distributions of planet mass, radius, density, internal structure and host star properties. (2) We will establish the dynamical context of these systems by determining the presence of outer companions and local density of stars (3) We will connect the measured demographics, dynamics and internal structure to wider formation and evolution theory. The combined results will transform our understanding not only of the in-desert planets but of the wider formation, structure and evolution of planetary systems.