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Fraser
2013-Feb-06, 05:50 PM
Artist’s impression of a rocky planet orbiting a red dwarf. Credit:*David A. Aguilar (CfA) We may literally be surrounded by potentially habitable exoplanets, according to new research by a team from the*Harvard-Smithsonian Center for Astrophysics. Using data gathered by NASA’s exoplanet-hunting Kepler spacecraft, the CfA researchers discovered that many red dwarf stars harbor planets, and [...]

More... (http://www.universetoday.com/99784/earthlike-exoplanets-are-all-around-us/)

galacsi
2013-Feb-06, 07:16 PM
Artistís impression of a rocky planet orbiting a red dwarf. Credit: David A. Aguilar (CfA) We may literally be surrounded by potentially habitable exoplanets, according to new research by a team from the Harvard-Smithsonian Center for Astrophysics. Using data gathered by NASAís exoplanet-hunting Kepler spacecraft, the CfA researchers discovered that many red dwarf stars harbor planets, and [...]

More... (http://www.universetoday.com/99784/earthlike-exoplanets-are-all-around-us/)

I don't know if in their definition of habitable zone they take into count the fact that probably these planet will be tidally locked. But I am nitpicking , it is great news ! And as these planet may be very near, we will have rather soon some atmosphere analysis. So may be , some other great news in the near future.

redshifter
2013-Feb-06, 08:28 PM
I think by 'habitable zone' they just mean the exoplanet is at a distance from the parent star such that temps on the planet are conducive to the existance of liquid water on the surface. I don't think it makes any assumptions that water is on the given planet or that it's not tidally locked, etc; just that based on its distance, liquid water could exist on its surface. Or in the case of a gas giant within the star's habitable zone, liquid water could potentially exist on exomoon(s) of the exo gas giant.

galacsi
2013-Feb-06, 09:58 PM
I think by 'habitable zone' they just mean the exoplanet is at a distance from the parent star such that temps on the planet are conducive to the existance of liquid water on the surface. I don't think it makes any assumptions that water is on the given planet or that it's not tidally locked, etc; just that based on its distance, liquid water could exist on its surface. Or in the case of a gas giant within the star's habitable zone, liquid water could potentially exist on exomoon(s) of the exo gas giant.

Yes , of course, but if a planet is tidally locked , only one hemisphere is bathed in the light of its sun , the other is in a perpetual night. Consequence : the lighted hemisphere receive a double amount of light.And the planet can be farther away from the sun and still have an habitable zone.

neilzero
2013-Feb-08, 03:03 AM
Very advanced beings can live almost anywhere. Does 2 times the size of Earth mean diameter 16,000 miles or 2 times the volume = diameter about 10,000 miles? Some less likely meanings are twice the cross sectional area or twice the mass. One g surface gravity is possible if twice the volume is low density, such as mostly lithium, beryllium, carbon, sodium and boron.
If the planet atmosphere has very little green house gas, and is tide locked, it can be as close as one million kilometers from the dimmist red dwarf stars = 400 c at the hottest part and colder than zero c at the coldest unlighted part = warm in the twilight zone, but very dry as water vapor is a powerful green house gas. Even with the Sun just above the horizon it is too hot for photosynthesis unless the plants can be cooled artificially. Worse the mostly red light is not very good for photosynthesis nor for human color perception. To be liveable, a bit farther away with lots of water vapor = steam in the hottest part of the lighted side. The atmosphere needs to be as dense as Earth, or more, to protect the biosphere from the powerful solar flares and CME = coronal mass ejection which most red dwarfs produce. A huge super conducting ring may be practical if the planet does not produce a strong magnetic field. Surface gravity less than one g may mean loss of atmosphere even with a strong magnetic field due to the intense solar flares and CME. Apparently the planet needs to be about as far from the star as Mercury for the brightest red dwarf stars that may not be tide locked, but possibly have low rotation rates like Mercury and Venus. Neil