Do you think life can form around around M-class Stars?

[Spaceception]

7 minutes ago, Bill Phil said:

Also, what's the average metallicity of M stars?

I think most are lowish, since they can't get a whole lot of mass due to being small.

[Bill Phil]

13 minutes ago, Spaceception said:

I think most are lowish, since they can't get a whole lot of mass due to being small.

Metallicity is a percentage.

I found out that they always have some metals, which means it's very likely that they aren't first gen stars.

[YNM]

Metallicity of dwarfs are not too low. First-gen stars are mostly massive, if not to merge later and becomes massive. From some of what I see red dwarfs are diverse in metallicity, ranging from negative (some reaches ~ -1) to above zero (but not close to one), in logarithmic scale wrt Sun's metal abundance.

[Bill Phil]

We should probably make this clear: metals in stars are anything that isn't H or He.

[GoSlash27]

I suspect the limit for life around a star isn't limited by the characteristics of the star itself, but rather the age of the materials around it. If you don't have heavy elements, you won't have a chemical foundation for life.

Elements like carbon and iron are pretty new in stellar terms.

Best,
-Slashy

[sevenperforce]

On 2/26/2016 at 6:42 PM, daniel l. said:

It depends on the class. An M2 for example should do fine. But an M9 would be too small, cold, and dense to support such a world as the habitable zone would end up inside the Roche limit.

A sufficiently dense ring structure inside the Roche limit could sustain windborne microbial life. 

6 hours ago, Bill Phil said:

Are we not going to bring up the extended habitable zone? The Sun's goes as far as Ceres, if only it was massive enough to have an atmosphere without human intervention.

Also, what's the average metallicity of M stars?

Average metallicity isn't really at issue; an M-class star can form in any protostellar nebula, so metallicity can be as high as you want it to be. In fact, IIRC, an M-class star in a nebula with available metal should have higher metallicity than a larger star, because larger stars more readily capture hydrogen and helium. 

The origin of life boils down to one thing: thermodynamics. Structures which can dissipate an energy flux last longer than structures which cannot. So what you need for life is an energy flux high enough to give life an edge, but not so high that every possible structure is continually being torched. 

Terran terrestrial life would probably not do well around an M-class star, with its high variability, but a world with subsurface oceans should be able to modulate the energy flux well enough to allow life to survive. 

[Bill Phil]

4 hours ago, GoSlash27 said:

I suspect the limit for life around a star isn't limited by the characteristics of the star itself, but rather the age of the materials around it. If you don't have heavy elements, you won't have a chemical foundation for life.

Elements like carbon and iron are pretty new in stellar terms.

Best,
-Slashy

Metalicity helps determine what the original elements in the nebula were, also determining the materials around it.

[fredinno]

9 hours ago, Spaceception said:

I think most are lowish, since they can't get a whole lot of mass due to being small.

M-types are actually quite varied in metallacity- smaller ones have more metallicity, as greater metallicity allows for smaller stars to fuze.

1 hour ago, sevenperforce said:

A sufficiently dense ring structure inside the Roche limit could sustain windborne microbial life. 

Average metallicity isn't really at issue; an M-class star can form in any protostellar nebula, so metallicity can be as high as you want it to be. In fact, IIRC, an M-class star in a nebula with available metal should have higher metallicity than a larger star, because larger stars more readily capture hydrogen and helium. 

The origin of life boils down to one thing: thermodynamics. Structures which can dissipate an energy flux last longer than structures which cannot. So what you need for life is an energy flux high enough to give life an edge, but not so high that every possible structure is continually being torched. 

Terran terrestrial life would probably not do well around an M-class star, with its high variability, but a world with subsurface oceans should be able to modulate the energy flux well enough to allow life to survive. 

I would be sceptical of "windborne" microbial life. There isn't any "wind" in a vaccum.But I can see bacteria barely surviving, if in a relatively sheltered area, but with just enough sunlight to get energy.

9 hours ago, Bill Phil said:

Are we not going to bring up the extended habitable zone? The Sun's goes as far as Ceres, if only it was massive enough to have an atmosphere without human intervention.

Also, what's the average metallicity of M stars?

Technically the "extended habitable zone" is larger than that if you allow for alternate biologies.

And Ceres would need to be a Super Earth to be able to be hot enough for life.

[sevenperforce]

14 hours ago, fredinno said:

I would be sceptical of "windborne" microbial life. There isn't any "wind" in a vaccum.But I can see bacteria barely surviving, if in a relatively sheltered area, but with just enough sunlight to get energy.

Well, "wind" is a bit of an exaggeration.