A temperate, rocky ‘super-Earth’ planet has been discovered transiting in front of a small star located about 12 parsecs (39 light years) away from our Sun, a Nature paper reports.

Jason Dittmann and colleagues report observations from the MEarth-South telescope array of an M dwarf star called LHS 1140; such stars, with masses less than 60 per cent that of the Sun, are the most common star class in our Galaxy. The authors find a planet, LHS 1140b, transiting LHS 1140 with a circular orbit that was probably present at formation. They use 144 radial-velocity measurements to precisely determine the planet’s radius (1.4 times that of Earth) and mass (6.6 times that of Earth), suggesting that it has a rocky composition. The planet’s cool insolation (low exposure to solar radiation) places it within the liquid-water ‘habitable zone’ of its host star.

The authors propose that LHS 1140b probably formed in its present location in a manner similar to Earth. They suggest that the small size of the host star and its proximity to us mean that current telescopes and those currently under construction might be able to search for specific gases in the planet’s atmosphere - if it has one.