The MEarth Project: A Transit Search for Rocky Planets in the Habitable Zones of Low-mass Stars

附近的低质量m矮星是凌日巡天特别有吸引力的目标，可以探测到在恒星宜居带内绕轨道运行的小型岩石行星。与类似太阳的类地行星不同，经过晚m矮星的类地行星呈现出足够深度的光度信号，可以让地面天文台探测到。此外，较低的恒星光度意味着，宜居带位于距离中心恒星的轨道距离较小的地方，这反过来又表明，凌日的几何概率较高，轨道周期较短，因此探测此类事件所需的时间跨度也较短，这应该有助于在宜居带探测行星。在这里，Charbonneau博士将领导一项为期三年的调查，对2000个最近的m型矮星进行调查，其节奏和灵敏度足以探测到半径小至地球两倍的宜居带行星。这项调查将在亚利桑那州南部霍普金斯山的地球天文台进行，该天文台由8个相同的40厘米ccd望远镜组成，这些望远镜位于一个单独的滚装外壳中。通过只对附近的、特征明确的目标进行顺序测量，earth克服了严重的误报污染问题，这种问题一直困扰着现有的宽视场测量。预计这项调查要么会探测到大型的、可居住的类地系外行星，要么会得出它们出现率的上限（99%的置信度）为17%。如果探测到，这些行星将(1)为类地系外行星的物理结构和组成模型提供第一个约束条件，(2)为低质量恒星周围行星形成的模型提供信息，(3)为后续的大气研究提供关键目标，这反过来将允许理解类地系外行星的大气化学和动力学。通过该项目，博士后、研究生和本科生将获得快速发展的系外行星科学领域的前沿研究机会。Charbonneau博士和项目参与者将通过在评审期刊上发表的一系列出版物、在通俗科学杂志上发表的文章、在天文学和跨学科研究会议上的演讲，以及面向公众的项目网页，广泛传播研究结果。

Nearby, low-mass M-dwarf stars are particularly attractive targets for transit surveys to detect small, rocky planets orbiting within their stellar habitable zones. Unlike their Sun-like counterparts, terrestrial planets transiting late M-dwarfs present a photometric signal that is of sufficient depth as to permit detection with ground-based observatories. Moreover, the low stellar luminosities imply that the habitable zones are located at small orbital distances from the central star, which in turn suggests detection of planets in their habitable zones should be facilitated by the higher geometric probability of a transit, and by the reduced orbital period and hence time span required to detect such an event.Here, Dr. Charbonneau will lead a 3-year survey of the 2000 nearest late M-dwarfs with a cadence and sensitivity sufficient to detect habitable-zone planets with radii as small as twice that of the Earth. The survey will be conducted at the MEarth Observatory at Mt Hopkins in southern Arizona, which consists of 8 identical 40cm CCD-based telescopes located in a single roll-off enclosure. By sequentially surveying only nearby, well-characterized targets, MEarth overcomes the severe problems of false-positive contamination that have plagued extant wide-field surveys. It is expected that the survey will either detect large, habitable-zone terrestrial exoplanets, or yield an upper limit (with 99% confidence) of 17% on their rate of occurrence. In the event of a detection, these planets will (1) provide the first constraints on models of the physical structure and composition of terrestrial exoplanets, (2) inform models of the planetary formation around low-mass stars, and (3) provide keystone targets for subsequent studies of their atmospheres, which in turn will permit an understanding of the atmospheric chemistry and dynamics for terrestrial exoplanets.Through this project, postdoctoral fellows, graduate students and undergraduates will be trained through access to a cutting-edge research opportunity in the rapidly-evolving field of exoplanet science. The results will be disseminated broadly by Dr. Charbonneau and the project participants through a series of publications in refereed journals, articles in popular science magazines, talks at astronomical and interdisciplinary research conferences, and a project webpage geared for the general public.