Proxima b may not be an only child after all.
In August 2016, astronomers announced that a roughly Earth-size exoplanet circles the closest star to the sun, the red dwarf Proxima Centauri, which lies a mere 4.2 light-years from us. (For perspective, the Milky Way galaxy’s spiral disk is about 100,000 light-years wide.)
That world, called Proxima b, orbits in Proxima Centauri’s “habitable zone,” the just-right range of distances from a star where liquid water could be stable on a world’s surface. So, there’s a chance that life as we know it may have taken root in the next solar system over from us. (How good that chance is remains a matter of considerable debate, however. For example, Proxima b is tidally locked to its host star, meaning it has a hot dayside and a cold nightside. And red dwarfs are very active stars, so powerful flares may have stripped the planet’s atmosphere long ago.)