At a distance of 1.295 parsecs, the red-dwarf Proxima Centauri ($alpha$ Centauri C, GL 551, HIP 70890, or simply Proxima) is the Suns closest stellar neighbor and one of the best studied low-mass stars. It has an effective temperature of only $sim$ 3050 K, a luminosity of $sim$0.1 per cent solar, a measured radius of 0.14 R$_odot$ and a mass of about 12 per cent the mass of the Sun. Although Proxima is considered a moderately active star, its rotation period is $sim$ 83 days, and its quiescent activity levels and X-ray luminosity are comparable to the Suns. New observations reveal the presence of a small planet orbiting Proxima with a minimum mass of 1.3~Earth masses and an orbital period of $sim$11.2 days. Its orbital semi-major axis is $sim0.05$ AU, with an equilibrium temperature in the range where water could be liquid on its surface.
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