Gliese 581 c

[XairstrikeXD]

i was wondering if our astronomers have found any "Proof" of life on Gliese 581 c or if its just suitable for life. oh and would having a red sun change anything as compared to our yellow sun

 

[Captain_Salty]

there's no "Proof" of life anywhere beyond earth.

 

[Solifugae]

Wasn't "d" the better in terms of potential, anyway?

 

[robnissen]

D is the better candidate, C is probably a little bit too close to be in the habitable (liquid water) zone. Plus, red dwarfs regularly send out large flares of hot gas, which would be more likely to hit C (because its closer). Finally, although both C and D are probably tidally locked, the odds are better that D is not tidally locked because its further away.

 

[XairstrikeXD]

D is the better candidate, C is probably a little bit too close to be in the habitable (liquid water) zone. Plus, red dwarfs regularly send out large flares of hot gas, which would be more likely to hit C (because its closer). Finally, although both C and D are probably tidally locked, the odds are better that D is not tidally locked because its further away.

tidally locked. what does that mean

 

[MeteorWayne]

It means the planet rotates once for every revolution in the orbit, so that one spot on the planet always faces the star (hence gets very hot) and the other hemisphere never sees the star at all (hence gets very cold).

This is just as the moon is tidally locked to the earth. We always see the same face of the moon (except for some minor wobbling called libration that allows us to peek just over the edge). The far side of the moon never sees the earth.

 

[XairstrikeXD]

oh so it would be to hot to sustain life on one side but on the other it would be to cold. so why isnt earth like that. did we just get lucky

 

[MeteorWayne]

Well, we are far enough from the sun so we are not tidally locked. 24 hour rotation alternates sun and darkness to keep temperatures relatively stable. We're also at a good distance so that water is liquid; the close in tidally locked planets are way too hot for liquid water on the sun side. How cold they are on the other side depends on the amount and type of atmosphere.

 

[reimk4526]

How close is Gliese 581 D to its host star? Also, What is the minimum distance and maximum distance that a planet has be in to support liquid water, in other words what range of distance does the Goldilocks zone cover?

 

[MeteorWayne]

All 4 planets of Gliese 581 orbit VERY close to the star, far closer than Mercury orbits our sun. 581 d has a distance of 0.22 AU compared to Mercury's 0.31 AU.

The habitable zone for any star (liquid water zone) varies due to the different energy output of each star. Gliese 581 is an M class dwarf, with only 0.2% of the output of the sun, so the habitable zone is much closer. At that distance from the sun, the surface of a planet would probably by close to melting.

 

[XairstrikeXD]

so if it had a very thick carbon dioxide atmoshpere like venus the dark side would be extremely hot, right.

 

[MeteorWayne]

Probably true, though it a subject still under investigation and modeling.