It is the second-closest known Earth-size exoplanet, after Proxima b.[27] It is calculated that Ross 128 b has a mass of 1.8 times the Earth, a radius 1.6 times that of the Earth, and orbits 20 times closer to its star than Earth orbits the Sun, intercepting only about 1.38 times more solar radiation than Earth,[2][12][28] increasing the chance of retaining an atmosphere over a geological timescale.