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K-type main-sequence stars, also known as orange dwarfs, 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 [1] to provide a temperature that allows liquid water to exist on the surface of a planet; they also remain stable in the main sequence longer than the Sun by burning their hydrogen ...
The separation between stars in a binary may range from less than one astronomical unit (AU, the average Earth–Sun distance) to several hundred. In latter instances, the gravitational effects will be negligible on a planet orbiting an otherwise suitable star and habitability potential will not be disrupted unless the orbit is highly eccentric.
A diagram depicting habitable zone boundaries across star type with September 2024 data, based on previous habitable zone diagrams. [1] Earth is plotted alongside 42 exoplanets with radii less than 2 times that of Earth or masses less than 5 times that of Earth, making them potentially rocky worlds in the habitable zone.
A superhabitable world is a hypothetical type of planet or moon that is better suited than Earth for the emergence and evolution of life. The concept was introduced in a 2014 paper by René Heller and John Armstrong, in which they criticized the language used in the search for habitable exoplanets and proposed clarifications. [2]
This is a list of confirmed exoplanets within the circumstellar habitable zone that are either under 10 Earth masses or smaller than 2.5 Earth radii, and thus have a chance of being rocky. [3] [1] Note that inclusion on this list does not guarantee habitability, and in particular the larger planets are more unlikely to have a rocky composition. [4]
K-type main-sequence stars are about three to four times as abundant as G-type main-sequence stars, making planet searches easier. [17] K-type stars emit less total ultraviolet and other ionizing radiation than G-type stars like the Sun (which can damage DNA and thus hamper the emergence of nucleic acid based life). In fact, many peak in the red.
Thus life habitable zones require and very stable star like the Sun, at ±0.1% solar luminosity change. [10] [11] Finding a stable star, like the Sun, is the search for a solar twin, with solar analogs that have been found. [12] Star metallicity, mass, age, color, and temperature all effect luminosity variations.
Of the main-sequence star types, stars more massive than 1.5 times that of the Sun (spectral types O, B, and A) age too quickly for advanced life to develop (using Earth as a guideline). On the other extreme, dwarfs of less than half the mass of the Sun (spectral type M) are likely to tidally lock planets within their habitable zone, along with ...