Mass, density and composition
The only physical property directly derivable from the observations (besides the orbital period) is the ratio of the radius of the planet to that of the central star, which follows from the amount of occultation of stellar light during a transit. This ratio was measured to be 0.021.This yields a planetary radius of 1.11±0.14 times that of Earth, taking into account uncertainty in the star's diameter and the degree of occultation. Thus, the planet is about 11% larger in radius than Earth (between 4.5% smaller and 26.5% larger), giving a volume about 1.37 times that of Earth (between 0.87 and 2.03 times as large).
There is a very wide range of possible masses that can be calculated by combining the radius with densities derived from possible planetary compositions; it could be a rocky terrestrial planet or a lower density ocean planet with a thick atmosphere. However, a massive hydrogen/helium (H/He) atmosphere is thought to be unlikely in a planet with a radius below 1.5 R⊕. Planets with a radius of more than 1.5 times that of Earth tend to accumulate the thick atmospheres that would make them less likely to be habitable. Red dwarfs emit a much stronger extreme ultraviolet (XUV) flux when young than later in life; the planet's primordial atmosphere would have been subjected to elevated photoevaporation during that period, which would probably have largely removed any H/He-rich envelope through hydrodynamic mass loss. Mass estimates range from 0.32 M⊕ for a pure water/ice composition to 3.77 M⊕ if made up entirely of iron (both implausible extremes). For a body with radius 1.11 R⊕, a composition similar to Earth’s (1/3 iron, 2/3 silicate rock) yields a mass of 1.44 M⊕, taking into account the higher density due to the higher average pressure compared to Earth.
