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from the in-star-trek-every-planet-is-habitable dept.
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:
It was previously assumed that planets with masses similar to Earth would be habitable simply because they were in the 'habitable zone'. However, when you consider how these planets evolve over billions of years this assumption turns out not to be true.
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.
(Score: 2) by HiThere on Friday May 27 2016, @07:20PM
I believe they aren't even measuring all the factors that need to go into making a planet "habitable", although I'm more talking about generating native life than people living on it.
E.g., I think it quite likely that a very large moon is necessary. It stabilizes the orbital inclination to the planet doesn't "tumble" (think gyroscope). There are also arguments about tides being necessary, but I haven't been able to decide about those.
OTOH, it's also possible that they are ignoring entire classes of habitable planets. E.g., it seems to me quite plausible that moons of giant planets could be habitable. Jupiter's moons are dubious because of it's strong magnetic fields (but perhaps life could evolve to handle that?), but IIUC equivalent moons of Saturn would be quite habitable if they were warm enough. And perhaps a methane based life exists on Titan.
Class M dwarfs tend to have strong flares, so they may be unlikely. (The planet needs to be pretty close to them to be habitable. It's been suggested, however, that class K dwarfs are reasonable. (The sun is a class G dwarf. (M are red, K are orange, G are yellow.) Probably only the K, M, and G dwarfs are stable for long enough to devlope life, but that's most stars in the galaxy. Unfortunately, M is the most common.
Now if native life has developed, it's likely to be a very inhospitable place to land. Massive allergy attacks. But if life hasn't developed there isn't likely to be much oxygen in the atmosphere.
All-in-all I think macro-life is the best approach to take.
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