The remaining two-thirds of the planets around these ubiquitous small stars are likely roasted by gravitational tides, sterilizing them.

Red dwarf stars, also called M dwarf or M-type star, the most numerous type of star in the universe and the smallest type of hydrogen-burning star. Red dwarf stars have masses from about 0.08 to 0.6 times that of the Sun.

Scientists now believe that 80 percent of the stars in our home galaxy, the Milky Way, are red dwarf stars. According to Jos de Bruijne, a scientist at the European Space Agency (ESA) who works on the galaxy-mapping Gaia mission, the current estimate is between 100 to 400 billion stars. This means 80 billion to 320 billion red dwarf stars and 24 billion to 96 billion with habitable zone planets.