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b0ru writes:

Earlier this month, a team of astronomers from the University of Liège, Belgium, and NASA, using the TRAPPIST instrument at the ESO site in La Silla, Chile, discovered three exoplanets with temperatures similar to those of the Earth and Venus orbiting an ultra-cool M class dwarf star. M dwarves makes up approximately 75 percent of the stars in our galaxy, and this discovery greatly improves the potential for habitable exoplanets.

A recent study from the Imperial College of London, however, suggests that, whilst these planets orbit cooler and less luminous stars, they may still be too hot to be habitable for life as we know it. Dr James Owen, Hubble Fellow and lead author of the study states:

The atmospheres of these exoplanets are estimated to make up rougly one percent of their planetary mass. By comparison, the mass of our atmosphere is roughly one millionth of the mass of our planet. This suggests an especially thick atmosphere which, given the resultant greenhouse effect, may render these exoplanets uninhabitable. Naturally, this problem is inherent of planets of Earth-like mass, or heavier; smaller planets, e.g. of Mars-like mass, may lose some of this atmospheric mass through evaporation, as we have observed in our own solar system. Further cataloging of the orbital systems of M class dwarf stars will identify these low mass exoplanets as candidates for the ongoing search for extra-solar life.

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