1 Mar 2017

Kepler-186 is a planetary system about 500 light-years away in the constellation Cygnus. It is made of one star and at least five planets.
The red dwarf star (spectral type M1V) has a radius and a mass half of those of the Sun and a surface temperature of 3500 °C. It is about 1000 times too faint to be visible with the naked eye.

The five planets, with radii between 1 and 1.4 Earth radii, have probably a solid surface. The outermost planet (Kepler-90 f), at 40% of the Sun-Earth distance of its star, is inside the “habitable zone” because the star is smaller and cooler than the Sun.
The star contains about half as much “metals” (all elements except hydrogen and helium) as the Sun, so the expectancy of large planets is reduced, but it is not excluded that additional low-mass planets remain to be discovered.