Kepler-11f

Kepler-11 is a G-type star,^[5] much like the Sun is, and is located 659 parsecs away in the Cygnus constellation. It has 95% the mass and 110% the radius of the Sun. Its mass and radius, combined with an approximate iron content (metallicity) of 0 and effective temperature of 5680 K, makes the star very similar to the Sun, though slightly more diffuse and slightly cooler. However, the star is approximately 1.74 times the age of the Sun, and is estimated to have existed for eight billion years. Kepler-11 has six known planets in orbit: Kepler-11b, Kepler-11c, Kepler-11d, Kepler-11e, Kepler-11f, and Kepler-11g.^[2] Kepler-11's five inner planets orbit closely to their host star, and their orbits would fit within that of Mercury's.^[1]

With an apparent magnitude of 14.2, Kepler-11 cannot be seen with the naked eye.^[2]

Kepler-11f is, at 2.3 times the mass of Earth, the least massive of the six planets discovered in the orbit of Kepler-11, although the planet's mass may range from 1.1 to 4.5, or from approximately that of Earth's mass to that of Kepler-10b, a rather large confidence interval.^[2] Its radius is the second smallest of the six planets discovered in the system at 2.61 times the radius of Earth. Kepler-11f has a density of about 0.7 g/cm³, comparable to that of the Solar System's least dense planet, Saturn. Kepler-11f is the fifth planet from Kepler-11, orbiting its host star every 46.68876 days at a distance of 0.25 AU. Its orbital eccentricity is unknown. In comparison, Mercury orbits the Sun every 87.97 days at a distance of 0.387 AU.^[6] Kepler-11f has an orbital inclination of 89.4°; it can be seen almost edge-on with respect to Earth. Its surface equilibrium temperature is 544 K, over twice the surface equilibrium temperature of Earth^[2] and about two-thirds the surface temperature of Venus.^[7]

Kepler-11f's low density, characteristic of the outer planets of the system, suggests that a hydrogen–helium atmosphere is present on these planets, classifying it as "gas dwarf" due to its small size and mass. The gaseous content of the planet is calculated at a few percent of its total mass, but the envelope accounts for 70-80% of the planet's total volume.^[8] Kepler-11f's low density is not shared by the planets Kepler-11b and Kepler-11c because stellar irradiation has reduced their atmospheres to a thin layer.^[1] The planets accreted such atmospheres because they formed within the first few million years of the system's existence, when a protoplanetary disk was still present.^[8][9]