PLANET hunters have detected what seems to be the smallest extrasolar planet so far, orbiting a red dwarf 22,000 light years away. Because red dwarfs are the most common type of star in the Milky Way, this might mean that Earth-like planets are abundant in our galaxy. In any case, it bodes well for “gravitational microlensing”, the technique used to find this exoplanet.
Most planet-hunting techniques pick up massive planets in tight orbits around their host stars. About 170 exoplanets have been found around sun-like stars and until now the smallest had weighed in at 7 Earth masses. Now…
