Faint red stars can build water worlds drip by drip
Sheer number of M dwarf systems makes them likely to host habitable exoplanets
MOST COMMON Most warm rocky planets around faint red stars (illustrated) are probably dry, but it’s likely that there are enough such worlds with oceans to outnumber all other habitable environments in the galaxy.
JPL-Caltech/NASA
HONOLULU — The stars likely to have the most habitable planets may also have the hardest time importing water to these worlds, Gijs Mulders reported August 5 at a meeting of the International Astronomical Union.
Faint, red orbs known as M dwarfs are the most common type of star in the Milky Way, making up about 80 percent of the stars in the galaxy. But these dwarf systems tend not to build the giant planets that are good at flinging icy asteroids at dry worlds, as is thought to have happened to Earth (SN: 5/16/15, p. 18). Recent computer simulations, however, show that lots of small boulders working together within a planet nursery can assume Jupiter’s and Saturn’s role by relocating ice deposits that help build livable locales.
“Even though water delivery is less efficient,” said
