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Although traditional definitions of the habitable zone assume that carbon dioxide and water vapor are the most important greenhouse gases (as they are on the Earth), [30] a study [50] led by Ramses Ramirez and co-author Lisa Kaltenegger has shown that the size of the habitable zone is greatly increased if prodigious volcanic outgassing of ...
The only ways in which potential life could avoid either an inferno or a deep freeze would be if the planet had an atmosphere thick enough to transfer the star's heat from the day side to the night side, or if there was a gas giant in the habitable zone, with a habitable moon, which would be locked to the planet instead of the star, allowing a ...
In astrobiology and planetary astrophysics, the galactic habitable zone is the region of a galaxy in which life is most likely to develop. The concept of a galactic habitable zone analyzes various factors, such as metallicity (the presence of elements heavier than hydrogen and helium) and the rate and density of major catastrophes such as supernovae, and uses these to calculate which regions ...
In 2012, scientists introduced a concept to define the habitable orbits of moons. [30] The concept is similar to the circumstellar habitable zone for planets orbiting a star, but for moons orbiting a planet. This inner border, which they call the circumplanetary habitable edge, delimits the region in which a moon can be habitable around its planet.
Under this definition, the inner edge of the habitable zone (i.e., the closest point to a star that a planet can be until it can no longer sustain liquid water) is determined by the outgoing longwave radiation limit beyond which the runaway greenhouse process occurs (e.g., the Simpson–Nakajima limit).
Habitability is conventionally defined by the equilibrium temperature of a planet, which is a function of the amount of incoming radiation; a planet is defined "habitable" if liquid water can exist on its surface although even planets with little external energy can harbour underground life.
Several other planets, such as Gliese 180 b, also appear to be examples of planets once considered potentially habitable but later found to be interior to the habitable zone. [ 1 ] Similarly, Tau Ceti e was thought to be likely habitable, [ 82 ] but with improved models of the circumstellar habitable zone, as of 2022 PHL does not consider it ...
The habitable zone around yellow dwarfs varies according to their size and luminosity, although the inner boundary is usually at 0.84 AU and the outer one at 1.67 in a G2V class dwarf like the Sun. [19] For a G5V class star with a radius of 0.95 R☉—smaller than the Sun—the habitable zone would correspond to the region located between 0.8 ...