3 ms·

Its a really really tiny star; quite small even as M-dwarfs go. So its habitable zone cannot but be where it could tidally lock the planet. Now, maybe some othe

Its a really really tiny star; quite small even as M-dwarfs go. So its habitable zone cannot but be where it could tidally lock the planet. Now, maybe some other resonances are possible, perhaps if there are other bigger planets around it helps (and I think they didn't exclude something up to a size of Neptune at about 1AU or beyond); don't know how the orbital mechanics of all this work out. But there were various modelling attempts to see how a tidal lock affects the climate, and it may not be a dealbreaker; not too thick an atmosphere could effectively transport that heat around, at least so that it doesn't risk freezing the atmosphere on the dark side and making it uninhabitable. But its just modelling so.. Maybe even more problematic is that a tidal lock could imply no internal dynamo, and so no protective magnetic field, and Proxima flares quite a lot, so it could have totally eroded its atmosphere and sterilized the surface with UV etc. Plus Proxima was much much hotter early on; would that period have permanently made the planet uninhabitable? We just know so very little about habitability of M-dwarfs, and particullary the really small ones; we'll just have to find out, Before we took a close look with probes, we thought Mars had lichens living on it, to explain its color variations or some such; there's no reason to think we have any more clue about M-dwarf planets than we had about mars then, for we have yet so study any. Good thing one just happens to be in our backyard :D Though realistically, perhaps it turns out easier to study more distant M-dwarf planets, because this one seems not to transit from our perspective. And I think we could study the spectra and hence atmospheric composition of transiting planets sooner than we can hope for direct imaging of them. Not perfectly sure though.

semi-extrinsic 10y ago
> We just know so wery little about habitability of M-dwarfs s/M-dwarfs/planets around any star/
- keithnoizu 10y ago
  Well we just know so very little about planets around any star, excluding 8 planets circling around one out of ~1,000,000,000,000,000,000,000 stars in the observable universe.
- WilliamDhalgren 10y ago
  yeah, kinda true -- though there's a great deal of extra uncertainty about M-dwarfs in particular in comparison to more sun-like stars, just because we did have this one example to study of that. But on the other hand, we see all kinds of planet types around all kinds of different stars that pose similar problems (say superearth habitability), so even that only applies to questions about planets more similar so some of the types we can find in our own solar system.
neolefty 10y ago
Why would a tidal lock imply no internal dynamo?
- WilliamDhalgren 10y ago
  well, you need rotation to create a dynamo, and these rotate rather slowly; once per orbit only. Now, it does seem this is still quite fast enough to produce a dynamo, but still the issue is whether it can still be strong enough to create a sufficient magnetosphere to save the atmosphere from completely eroding away, given both how close and how active Proxima Cent. is . Here's a paper that tries to see how much atmosphere planets in habitable zones around red dwarfs could lose given the activity of the star and the magnetosphere they could produce: - http://arxiv.org/abs/1204.0275 http://arxiv.org/abs/1204.0275 . I guess its quite possible various other models have different takes on it, but anyhow that's the worry. I hope we'll see such modelling work done for Proxima Cent. b soon.

semi-extrinsic 10y ago

> We just know so wery little about habitability of M-dwarfs s/M-dwarfs/planets around any star/

keithnoizu 10y ago
Well we just know so very little about planets around any star, excluding 8 planets circling around one out of ~1,000,000,000,000,000,000,000 stars in the observable universe.
WilliamDhalgren 10y ago
yeah, kinda true -- though there's a great deal of extra uncertainty about M-dwarfs in particular in comparison to more sun-like stars, just because we did have this one example to study of that. But on the other hand, we see all kinds of planet types around all kinds of different stars that pose similar problems (say superearth habitability), so even that only applies to questions about planets more similar so some of the types we can find in our own solar system.

neolefty 10y ago

Why would a tidal lock imply no internal dynamo?

WilliamDhalgren 10y ago
well, you need rotation to create a dynamo, and these rotate rather slowly; once per orbit only. Now, it does seem this is still quite fast enough to produce a dynamo, but still the issue is whether it can still be strong enough to create a sufficient magnetosphere to save the atmosphere from completely eroding away, given both how close and how active Proxima Cent. is . Here's a paper that tries to see how much atmosphere planets in habitable zones around red dwarfs could lose given the activity of the star and the magnetosphere they could produce: - http://arxiv.org/abs/1204.0275 http://arxiv.org/abs/1204.0275 . I guess its quite possible various other models have different takes on it, but anyhow that's the worry. I hope we'll see such modelling work done for Proxima Cent. b soon.