The MEarth Project is a ground-based photometric survey to find planets transiting the closest and smallest main-sequence stars .
In its first four years , MEarth discovered one transiting exoplanet , the 2.7 { R _ { \earth } } planet GJ1214b .
Here , we answer an outstanding question : in light of the bounty of small planets transiting small stars uncovered by the Kepler mission , should MEarth have found more than just one planet so far ?
We estimate MEarth ’ s ensemble sensitivity to exoplanets by performing end-to-end simulations of 1.25 \times 10 ^ { 6 } observations of 988 nearby mid-to-late M dwarfs , gathered by MEarth between October 2008 and June 2012 .
For 2 - 4 { R _ { \earth } } planets , we compare this sensitivity to results from Kepler and find that MEarth should have found planets at a rate of 0.05 - 0.36 planets/year in its first four years .
As part of this analysis , we provide new analytic fits to the Kepler early M dwarf planet occurrence distribution .
When extrapolating between Kepler ’ s early M dwarfs and MEarth ’ s mid-to-late M dwarfs , we find that assuming the planet occurrence distribution stays fixed with respect to planetary equilibrium temperature provides a good match to our detection of a planet with GJ1214b ’ s observed properties .
For larger planets , we find that the warm ( 600 - 700 K ) , Neptune-sized ( 4 { R _ { \earth } } ) exoplanets that transit early M dwarfs like Gl436 and GJ3470 occur at a rate of < 0.15 /star ( at 95 % confidence ) around MEarth ’ s later M dwarf targets .
We describe a strategy with which MEarth can increase its expected planet yield by 2.5 \times without new telescopes , by shifting its sensitivity toward the smaller and cooler exoplanets that Kepler has demonstrated to be abundant .