Most red dwarfs are born of satellites with dense atmospheres.
Astronomers from the US and the UK found that many earth-like exoplanets located in the habitable zone around its star, uninhabitable. Their study published in the journal Monthly Notices of the Royal Astronomical Society.
In the case that the sizes of exoplanets comparable to earth’s, and it is located in the habitable zone (in order to exist liquid water), scientists suspect the presence of the planet conditions for life. A new study of astronomers has shown that since cost to do not always.
Scientists have considered the stars of class M, which are the most common bodies in the milky Way (they account for 75 percent of all stars). These include red dwarfs, which are three times lighter than the Sun and two to three times fainter than it. Recently in the vicinity of stars of class M have found many exoplanets.
Most satellites of red dwarf born with thick atmospheres of hydrogen and helium, which account for about one percent of the mass of the exoplanet (for the Earth this option is ten thousand times less). The greenhouse effect on a celestial body with such a dense atmosphere would be too pronounced, which would lead to the impossibility of the existence on it of liquid water and life.
However, x-ray and ultraviolet radiation from the parent star would allow, according to scientists, to evaporate most part of the atmosphere and would make it less dense and livable. New modeling has shown that this is not always the case.
The study notes that the loss of the atmosphere earth-like exoplanet in the vicinity of the red dwarf is determined by two factors: the mass of a celestial body and its location in the zone of habitability.
So, if a planet is at the inner edge of this zone, and the mass of its nucleus is not more than 90 percent of the mass of the Earth, the radiation from red dwarf will be enough for the loss of a sufficient amount of the gas envelope and the appearance of a good live conditions. This is true even for cases when the mass of the atmosphere is initially one percent by weight of the total celestial body.
However, if earth-like planet located on the outer edge of the habitable zone, for the origin of life – it should be not more than 0.8 times heavier than Earth. Meanwhile, any object whose mass is comparable to earth will not be habitable, the study showed.
