Habitability of yellow dwarf systems
[8][9] However, technological limitations make it difficult to find these objects due to the infrequency of their transits, a consequence of the distance that separates them from their stars or semi-major axis.
[15][16] Studies by the team of Edward Guinan, an astrophysicist at Villanova University, reveal that the Sun rotated ten times faster in its early days.
Since the rotation speed of a star affects its magnetic field, the Sun's X-ray and UV emissions were hundreds of times more intense than they are today.
[21] Beyond the outer limit of the habitable zone, temperatures would be low enough to allow CO2 condensation, which would lead to an increase in albedo and a feedback reduction of the greenhouse effect until a permanent global glaciation would occur.
[1] One goal in exoplanetary research is to find an object that has the main characteristics of our planet, such as radius, mass, temperature, atmospheric composition and belonging to a star similar to the Sun.
[9][29] Based on the serious problems for planetary habitability presented by red dwarf systems and stellar bodies of type F or higher, the only stars that might offer a bearable scenario for life would be those of type K and G.[1] Solar analogs used to be considered as the most likely candidates to host a solar-like planetary system, and as the best positioned to support carbon-based life forms and liquid water oceans.
[4] Finally, yellow dwarfs have a much shorter initial phase of intense stellar activity than K-type stars, which allows planets belonging to solar analogs to preserve their primordial atmospheres more easily and to maintain them for much of the main sequence.
[28] As a consequence, most of the exoplanets detected are either excessively hot[37] or belong to low-mass stars, whose habitable zone is close to them and any object orbiting in this region will have a significantly shorter year than the Earth.
[10] Planetary bodies belonging to the habitable zone of yellow dwarfs, such as Kepler-22b, Kepler-452b or Earth, take hundreds of days to complete an orbit around their star.
[38] The higher luminosity of these stars, the scarcity of transits and the semi-major axis of their planets located in the habitable zone reduce the probabilities of detecting this class of objects and considerably increase the number of false positives, as in the cases of KOI-5123.01 and KOI-5927.01.
[39][40] The ground-based and orbital observatories projected for the next ten years may increase the discoveries of Earth analogs in yellow dwarf systems.
[45] Its radius of about 1.6 R⊕[46] places it right on the boundary separating telluric planets from mini-Neptunes established by the team of Courtney Dressing, a researcher at the Harvard-Smithsonian Center for Astrophysics (CfA).
[45] If it is an Earth-like telluric object, it is likely to have a higher concentration of clouds, intense volcanic activity, and is about to suffer an uncontrolled greenhouse effect similar to that of Venus due to the constant increase in the luminosity of its star, after having remained throughout the main sequence in its habitable zone.
