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

在附近，低质量的M-矮星是凌日探测的特别有吸引力的目标，目的是探测在其恒星宜居带内运行的小型岩石行星。与类似太阳的行星不同，经过M矮星晚期的类地行星呈现的光度信号具有足够的深度，可以用地面观测站进行探测。此外，恒星的低亮度意味着宜居带距离中央恒星的轨道距离很小，这反过来又表明，较高的凌日几何概率，以及较短的轨道周期和探测此类事件所需的时间跨度，应该有助于探测到宜居带中的行星。在这里，沙博诺博士将领导一项为期3年的调查，对距离最近的2000颗M型晚期矮星进行调查，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上的MEARTH天文台进行，该天文台由8个相同的40厘米CCD望远镜组成，安装在一个可滚转的外壳中。通过只顺序地调查附近的、特征良好的目标，MEARTH克服了困扰现有广泛领域调查的严重的假阳性污染问题。预计这次调查将探测到大型的、可居住的类地系外行星，或者产生17%的出现率上限(以99%的置信度)。一旦探测到，这些行星将(1)提供关于系外行星物理结构和组成模型的第一批约束，(2)提供围绕低质量恒星的行星形成模型，以及(3)为随后对其大气层的研究提供关键目标，这反过来将使人们能够了解类地系外行星的大气化学和动力学。通过该项目，博士后研究员、研究生和本科生将通过获得快速发展的系外行星科学领域的前沿研究机会进行培训。Charbonneau博士和项目参与者将通过在相关期刊上发表的一系列出版物、科普杂志上的文章、天文学和跨学科研究会议上的演讲以及面向普通公众的项目网页，广泛传播这一成果。

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.