Discovery, characterisation and understanding of extrasolar telluric and ice planets with transits

凌日的太阳系外大地行星和冰行星的发现、表征和理解

• 批准号: ST/F011083/1
• 负责人: Frederic Pont
• 金额: $ 59.86万
• 依托单位: UNIVERSITY OF EXETER
• 依托单位国家: 英国
• 项目类别: Fellowship
• 财政年份: 2008
• 资助国家: 英国
• 起止时间: 2008 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=ST%2FF011083%2F1
• 关键词: Discovery; characterisation; understanding; extrasolar; telluric

Until recently, we had only one planetary system, the Solar system, against which to test our ideas of how planets form and evolve. Since the discovery, in 1995, of the first planet found around another normal star, over 200 other extra-solar planets have been discovered, and we are starting to place the Earth and the Solar system in their cosmic context. Exploration to date focussed on gaseous giant planets, but new instruments and space missions now make it possible to detect and study smaller planets, mainly composed of ice or water and rocks, such as Uranus or Neptune-like planets, but also hypothetical very massive rocky planets / 'super Earths' / or planets with a deep surface layer of water / 'ocean planets'. Early results suggest these rock/ice planets are relatively common around Sun-like stars. Detecting them is a major step towards discovering extrasolar planets capable of supporting life, but also teaches us about the way Earth-like planets form. My proposal aims to contribute to all stages of the study of these planets: discovery, characterisation, and understanding. The first step is to discover the planets, for which I use two complementary methods. The radial velocity method measures the reflex motion of the star due to the pull of the planet, and I will pursue it with the advanced spectrographs HARPS and SOPHIE (at ESO in Chile and OHP in France) in collaboration with European astronomers. My main expertise is with the second method, the transit method, which measures the dimming of the star as a planet passes in front of it. I have already participated in the detection of transits for a dozen gaseous giant planets, as well as the only transiting Neptune-mass planet known yet (GJ 436b). I will search for new transiting rock/ice planets in data from the CoRoT space telescope, and for transits of known low-mass planets with small ground-based telescopes. The next step is to measure their properties. Uniquely powerful observations are possible when a planet transits its parent star, or passes behind it on the opposite side of the orbit, which reveal key properties such as mass, radius, bulk composition, and atmospheric temperature. The Hubble Space Telescope (HST) and Spitzer Infrared Space Telescope Facility (SIRTF) have opened up this field in the past few years. I recently led a team, which made the first detection of a high altitude haze in the atmosphere of the giant planet companion to the bright star HD 189733 using the HST, and have similar observations scheduled soon for GJ. Over the next few years, I will continue using space facilities to characterise newly identified low-mass planets. I also intend to use smaller ground-based telescopes to monitor transits of known planets. These time-critical observations are difficult to schedule at normal sites, and Antarctica, with months of uninterrupted darkness, has emerged as a promising alternative. I take part in a project to install a small telescope for transit observations at Dome C on the central Antarctic plateau, where the Exeter Astrophysics Group is already involved with a number of astronomical projects. The ultimate aim of this program is to improve our understanding of the formation, evolution and structure of rock/ice planets, by comparing the numbers and properties of different types of detected planets to what theoretical models predict. This requires accounting not only for what we see, but also for what we miss. I have investigated the biases in commonly used planet detection methods, and the degree of uncertainty on the properties we measure. I have also, with colleagues specialised in modelling stellar structure, started developing structure models for rock/ice planets, which I plan to extend by collaborating with planet formation specialists. I will then apply this to the results of the observational projects mentioned earlier to build up an end-to-end view of the statistical implications of their results.

直到最近，我们只有一个行星系统，即太阳系，来测试我们关于行星如何形成和演化的想法。自1995年发现第一颗围绕另一颗正常星星运行的行星以来，已经发现了200多颗太阳系外行星，我们开始将地球和太阳系置于其宇宙背景中。迄今为止的探索主要集中在气态巨行星上，但新的仪器和太空任务现在使探测和研究较小的行星成为可能，这些行星主要由冰或水和岩石组成，例如天王星或类海王星行星，但也有假设的非常巨大的岩石行星/“超级地球”/或具有深层水表面的行星/“海洋行星”。早期的结果表明，这些岩石/冰行星在类太阳恒星周围相对常见。探测它们是发现能够支持生命的太阳系外行星的重要一步，也让我们了解了类地行星的形成方式。我的建议旨在为这些行星研究的所有阶段做出贡献：发现，表征和理解。第一步是发现行星，为此我使用两种互补的方法。径向速度方法测量了由于行星引力而导致的星星的反射运动，我将与欧洲天文学家合作，使用先进的光谱仪HARPS和SOPHIE（位于智利的ESO和法国的OHP）来研究它。我的主要专长是第二种方法--凌日法。当一颗行星从星星前面经过时，凌日法测量的是恒星的亮度。我已经参与了十几颗气态巨行星的凌日探测，以及目前已知的唯一一颗海王星质量的凌日行星（GJ 436 b）。我将在CoRoT太空望远镜的数据中寻找新的凌日岩石/冰行星，并使用小型地面望远镜寻找已知的低质量行星。下一步是测量它们的属性。当一颗行星经过它的母星星时，或者在轨道的另一边从它的后面经过时，就有可能进行独特而强大的观测，这揭示了诸如质量、半径、体积组成和大气温度等关键特性。哈勃太空望远镜（HST）和斯皮策红外太空望远镜设施（SIRTF）在过去几年中开辟了这一领域。我最近领导了一个团队，他们使用HST首次探测到了明亮星星HD 189733的巨行星伴星大气层中的高海拔薄雾，并计划很快对GJ进行类似的观测。在接下来的几年里，我将继续使用太空设施来探测新发现的低质量行星。我还打算使用较小的地面望远镜来监测已知行星的凌日。这些时间紧迫的观测很难安排在正常的地点，而南极洲有几个月不间断的黑暗，已经成为一个有希望的替代方案。我参加了一个项目，在南极高原中部的圆顶C安装一个小型望远镜进行凌日观测，埃克塞特天体物理小组已经参与了一些天文项目。该计划的最终目的是通过将不同类型探测到的行星的数量和性质与理论模型预测的进行比较，提高我们对岩石/冰行星的形成，演化和结构的理解。这不仅要求对我们看到的东西进行核算，而且还要求对我们错过的东西进行核算。我研究了常用行星探测方法的偏差，以及我们测量的属性的不确定性程度。我还与专门从事恒星结构建模的同事一起，开始开发岩石/冰行星的结构模型，我计划通过与行星形成专家合作来扩展这些模型。然后，我将把它应用到前面提到的观测项目的结果中，以建立一个关于其结果的统计含义的端到端视图。