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

Harvard University, Cambridge MA

Investigators

Abstract

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.