The Transit Spectrum of Extrasolar Planet HD 209458b

除了（通常最小的）质量、（很少的）半径和加热之外，几乎没有对任何太阳系外行星进行过测量。发现的“热木星”系外行星是完全没有预料到的，可能是一种不同于木星和海王星的新型巨行星。模型表明，围绕恒星HD 209458的行星形成时是热的，但它是如何形成的还没有完全一致的假设。测量化学物质的丰度，云的位置，甚至是一颗行星的温度，都将指导现在几乎不受约束的建模工作。研究人员正在开发一种分析系外行星凌日光谱的新技术，并将其应用于对凌日系外行星HD 209458b的观测。他们在四个天文台成功地观察了这个系统16个晚上。这些数据在红外波段范围很广。富含水、甲烷和一氧化碳分子吸收的区域。在运输过程中，这颗行星的大气应该会将恒星光谱调节到千分之一，这为直接测量这颗“热木星”行星提供了一种方法。只有新颖的技术才能探测到如此微弱的地面信号。研究人员的丰富和高质量的数据使一个更好的方法，基于主成分分析，可以独立于模型推导出凌日调制，因为行星的特征应该在凌日开始和结束时打开和关闭。更广泛的影响：公众对其他行星上的水（甚至是热木星上的水蒸气）很感兴趣，因为它们与生命和可居住的行星有关。这个项目非常引人注目，以至于外行人都有兴趣了解光谱学是如何工作的，所以它是一个有用的教育例子。这些数据是如此详尽，无论是成功还是失败，都将为基于空间的太阳系外行星科学提供宝贵的经验。

AST 0307841PI HarringtonLittle has been measured for any extrasolar planet except (usually minimum) mass, (rarely) radius, and heating. The "hot Jupiter" extrasolar planets found were entirely unpredicted and may be a new class of giant planet distinct from Jupiters and Neptunes. Models indicate that the planet around the star HD 209458 formed hot, but there are no entirely consistent scenarios for how it formed. Measuring chemical abundances, cloud locations, and the temperature of even one planet would guide modeling efforts that are now almost unconstrained. The investigators are developing a new technique for analyzing extrasolar planet transit spectra, and will apply it to their observations of the transiting extrasolar planet HD 209458b. They observed this system successfully on 16 nights at four observatories. The data span a wide range in the infrared. a region rich in molecular absorptions from water, methane, and carbon monoxide. In transit, the planet's atmosphere should modulate the stellar spectrum by a part in a thousand, providing a way to measure this "hot Jupiter" planet directly. Only novel techniques can detect such a weak signal from the ground. The investigators' abundant and high-quality data enable a better approach, based on principal components analysis, that can derive the transit modulation independently of a model since the planetary signature should turn on and off at the start and end of the transit.Broader Impact: The public is interested in water on other planets (even water vapor on hot Jupiters), because of the connection with life and habitable planets. The project is compelling enough that lay people tend to be interested in learning how the spectroscopy works, so it is a useful educational example. The data are so exhaustive that either success or failure will provide valuable lessons for space-based extrasolar planetary science.