It's the axial tilt, I tell you!

[FiahOwl]

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[phinehas]

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[smjjames]

What about red dwarfs in a close binary of days or hours? The combined radiation would push the habitable zone out further, so there is a possibility of planets retaining axial tilt that way.

Also, this: "Heller and his colleagues have limited their analysis to planets and stars, though three- and four-body simulations are in the works." So chalk it up to 'we just don't know for sure yet'

Despite what the article says about stars with masses 90% that of the sun, we shouldn't just rule out K class stars, which go down to about 70% solar mass I think.

[Omnigeek6]

I'm a bit skeptical.

http://en.wikipedia.org/wiki/Planetary_habitability#Red_dwarf_systems

"This pessimism has been tempered by research. Studies by Robert Haberle and Manoj Joshi of NASA's Ames Research Center in California have shown that a planet's atmosphere (assuming it included greenhouse gases CO2 and H2O) need only be 100 mbs, or 10% of Earth's atmosphere, for the star's heat to be effectively carried to the night side.[47] This is well within the levels required for photosynthesis, though water would still remain frozen on the dark side in some of their models. Martin Heath of Greenwich Community College, has shown that seawater, too, could be effectively circulated without freezing solid if the ocean basins were deep enough to allow free flow beneath the night side's ice cap. Further research—including a consideration of the amount of photosynthetically active radiation—suggested that tidally locked planets in red dwarf systems might at least be habitable for higher plants.[48]"

If an atmosphere much thinner than Earth's can circulate heat on a tidally locked planet, then I don't think any earthlike planet with a low axis tilt is in danger of "atmospheric collapse."

Note also that many super-earths will be "ocean planets," and have both a global ocean and a thick water vapor atmosphere helping circulate heat.



This doesn't seem to be an innovative study, just reinventing the wheel with tidally locked planets, combined with a good dose of "life can only exist on planets which are exactly like Earth."