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-矮星是凌日巡天特别有吸引力的目标，可以探测在其恒星可居住区内运行的小型岩石行星。与类似太阳的行星不同的是，类地行星经过晚M矮星时会发出光度信号，其深度足以让地面天文台探测到。此外，恒星的低光度意味着可居住区位于距离中心星星很小的轨道距离处，这反过来又表明，通过更高的凌日几何概率，以及减少轨道周期和因此所需的时间跨度来检测这样的事件，应该有助于检测可居住区中的行星。Charbonneau博士将领导对2000颗最近的晚M矮星进行为期3年的调查，其节奏和灵敏度足以检测半径为地球两倍的可居住区行星。该调查将在亚利桑那州南部霍普金斯山的MEarth天文台进行，该天文台由位于单个滚降外壳中的8个相同的40厘米CCD望远镜组成。通过只对附近特征明确的目标进行连续测量，MEarth克服了困扰现有宽场测量的假阳性污染的严重问题。预计这项调查将探测到大型的可居住区类地系外行星，或者产生17%的出现率上限（99%的置信度）。 一旦被探测到，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）为低质量恒星周围的行星形成模型提供信息，（3）为随后对其大气层的研究提供关键目标。这反过来将有助于了解地球系外行星的大气化学和动力学。通过这个项目，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尖端研究机会接受培训。Charbonneau博士和项目参与者将通过在权威期刊上发表的一系列出版物、在科普杂志上发表的文章、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.