Habitability of K-type main-sequence star systems
K-type main-sequence stars may be candidates for supporting extraterrestrial life. These stars are known as "Goldilocks stars" as they emit enough radiation in the non-UV ray spectrum to provide a temperature that allows liquid water to exist on the surface of a planet; they also remain stable in the main phase longer than the Sun, allowing more time for life to form on a planet around a K-type main-sequence star. The planet's habitable zone, ranging from 0.1–0.4 to 0.3–1.3 astronomical units (AU), depending on the size of the star, is often far enough from the star so as not to be tidally locked to the star, and to have a sufficiently low solar flare activity not to be lethal to life. In comparison, red dwarf stars have too much solar activity and quickly tidally lock the planets in their habitable zones, making them less suitable for life. The odds of intelligent life arising may be better on planets around K-type main-sequence stars than around Sun-like stars, given the extra time available for it to evolve. Few planets thus far have been found around K-type main-sequence stars, but those that have are potential candidates for extraterrestrial life.
A K-type star's habitable zone approximately ranges between 0.1–0.4 to 0.3–1.3 AU from the star. Here, exoplanets will receive only a relatively small amount of ultraviolet radiation, especially so towards the outer edge. This is favorable to support life, as it means that there is enough radiated energy to allow liquid water to exist on the surface, but not so much radiation as to destroy life.
Potentially habitable planets around K-type main-sequence stars
A super-Earth orbiting a K-type main-sequence star called HD 85512 b, as well as a planet named HR 7722 c, with ≥24 ± 5 M⊕ (Earth mass) seem to have habitability potential. There may be many more, and the Kepler telescope is currently searching for planets around K-type main-sequence stars. Kepler-62 is an example of a discovery by Kepler of a system consisting of a K-type dwarf with potentially habitable planets orbiting it.
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