A paper describing this discovery appears in the 20 April 2017 issue of Nature, and is summarized in a press release from the Harvard Center for Astrophysics. We make our PDF preprint of the paper available here.
The MEarth Project is delighted to announce the discovery of LHS 1140b, a rocky planet 1.4 times the size of the Earth. LHS 1140b transits a star that is both very small (1/5 the size of the Sun) and very nearby (only 40 lightyears away). It also receives similar amounts of energy from its star that Earth does from the Sun, which means it may have liquid water on its surface!