Guillem Anglada-Escudo, et al., report that at a distance of 1.295 parsecs, the red dwarf Proxima Centauri (Centauri C, GL 551, HIP 70890 or simply Proxima) is the Sun closest stellar neighbor and one of the best-studied low-mass stars. It has an effective temperature of only around 3,050 degrees kelvin, a luminosity of 0.15% of that of the Sun, a measured radius of 14% of the radius of the Sun and a mass of about 12% of the mass of the Sun.
Although Proxima is considered a moderately active star, its rotation period is about 83 days and its quiescent activity levels and X-ray luminosity are comparable to those of the Sun.They report observations that reveal the presence of a small planet with a minimum mass of about 1.3 Earth masses orbiting Proxima with a period of approximately 11.2 days at a semi-major-axis distance of around 0.05 astronomical units. Its equilibrium temperature is within the range where water could be liquid on its surface.
The planet cannot yet be ruled out at longer orbital periods and Doppler semi- amplitudes of <3 ms-1. By numerical integration of some putative orbits, they verified that the presence of such a planet would not compromise the orbital stability of Proxima b.The habitability of planets like Proxima b, in the sense of sustaining an atmosphere and liquid water on its surface, is a matter of intense debate. The most common arguments against habitability are tidal locking, strong stellar magnetic fields, strong flares and high ultraviolet and X-ray fluxes, but none of these have been proven.
Tidal locking does not preclude a stable atmosphere via global atmospheric circulation and heat redistribution. The average global magnetic flux density of Proxima is 600± 150 G, which is quite large compared with that of the Sun (1G). However, because of its close orbit to Proxima, Proxima b suffers from major X-ray fluxes but it may be protected by a strong magnetic field around Proxima b.
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