The nearest to the Sun Earth-like candidate exoplanet Proxima b was found to orbit the nearest to the Sun red dwarf star Proxima Centauri, only 4.25 light years* away. Its minimum mass of 1.3 Earths was determined from stellar radial velocity. Since red dwarfs radiate significantly less energy than our Sun, this potentially habitable planet capable of bearing liquid water on its surface resides only 0.05 AU* from its star, which is 8 times closer than Mercury to the Sun.

Consequently, according to Kepler’s laws, it takes only 11.2 days for this planet to complete one orbit around the star (which we call a year). How long the day on this planet is unknown, but since it is so close to the star it can rotate synchronously with its orbital motion, like the Moon around the Earth (1:1 resonance, i.e. one Proxima b day = 11.2 of our days), or be in the 3:2 resonance as Mercury (i.e., one Proxima b day = 7.5 of our days). This planet will be the primary target for searching for life signatures.

* light year = distance which light travels during one terrestrial year

* AU = Astronomical Unit, mean distance between the Sun and Earth

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