All told, these main sequence stars make up about 70 percent of the estimated 100 billion stars in the Milky Way. “So by my back of the envelope calculation there are tens of billions of potentially habitable planets in the galaxy,” Batalha said. read more
Extrapolating out to the rest of the galaxy, scientists estimate that the Milky Way could contain upwards of 50 billion planet, 500 million of which could be in the habitable zone. And of course this is only for our own galaxy, there are billions upon billions more galaxies in the universe. read more
In November 2013, astronomers reported, based on Kepler space mission data, that there could be as many as 40 billion Earth-sized planets orbiting in the habitable zones of Sun-like stars and red dwarfs in the Milky Way, 11 billion of which may be orbiting Sun-like stars. read more
In the Milky Way, about 1 in 5 stars that are like our sun in size, color and age have planets that are roughly Earth's size and are in the habitable zone where life-crucial water can be liquid, according to intricate calculations based on four years of observations from NASA's now-crippled Kepler telescope. read more