Earth-Like Planet around Proxima?

[Excited Penguin]

What is the Goldilocks zone?

[Anomalocaris]

Twice as much gravity? How would complex terrestial life forms or vertebraes be, theoretically speaking?

Why is the threshold for complex terrestrial life between one and two earth gravities?

[RozKek]

Twice as much gravity? How would complex terrestial life forms or vertebraes be, theoretically speaking?

If theres liquid water gravity becomes less of an issue.

Terrestial=on land. I'm interested in how complex life on land would be.

[Anomalocaris]

What is the Goldilocks zone?

It is a range of distances from the parent star within which exposed liquid water can exist on the surface of any planet with the right atmospheric conditions. Or in other words water based life is not immediately precluded from existing on the surface of a planet.

Given evidence that earthly life may not have originate on earth's surface but deep under water, perhaps underground, and the conditions similar to those under which life may have first evolved on earth appear common inside the solar system's moons residing well outside of solar system's own Goldilocks zone, I wonder if the focus on Goldilocks zone is too anthropocentric.

[Anomalocaris]

If theres liquid water gravity becomes less of an issue.

Terrestial=on land. I'm interested in how complex life on land would be.

Why?

[RozKek]

Terrestial=on land. I'm interested in how complex life on land would be.

Why?

Just curious?

[Alex K]

If theres liquid water gravity becomes less of an issue.

Terrestial=on land. I'm interested in how complex life on land would be.

With twice the gravity? Simply somewhat sturdier at the same size, I'd guess.
Animals on Earth must be disproportionally stronger and more heavy-set the bigger they get (you can't
simply proportionally zoom a Mouse to 10 times the size, it would be way to weak to support itself, because
the weight goes with the size cubed, but the area of bones only with the size squared).
So, if you have twice the gravity, on that planet you'd have the creatures of human size look as heavily built and sturdy
as creatures on Earth somewhat larger than humans would be.

[Alex K]

None of the above.  But the term 'Earth-like planet' drives me spare.

Boru

I feel you so much.
In the German news item, they have an even worse one - they'd say "The search for the second Earth".
I complained on their Twitter feed about that wording precisely.

[Anomalocaris]

Regarding how complex terrestrial life would be under 2Gs:

2 Gravity itself probably doesn't put a tight limit on complexity of individual organism or ecosystem but probably put a appreciable limit on maximum size of any motile organism in the terrestrial ecosystem.

Reasonably well conditioned humans can lift their own body weight as additional load, and pilots can endure 2Gs indefinitely.   So clearly twice earth gravity is no insurmountable structural stress barrier to terrestrial animals roughly human sized, and broadly built like earthly vertebrates using similar mineralized skeletons.   They might be on average slower in ground movement under their own gravity conditions.

We know ants can carry loads 20 times their own weight and still get around fine.   So it seems small but still very macroscopic terrestrial motile animals can exist at least up to 20 earth gravity from structural strength point of view.

I don't think any draft animals or animals of any other kind appreciably larger than humans can carry their own weight as additional load.  So I will guess roughly human sized is near the upper limit of size of animal built along earth vertebrate lines that could get about under 2 Gs.  

Of course structural and muscular strength is not the only limit.   There is probably a tighter limit defined by the impact of higher gravity on the efficiency of locomotion.   Sometime before gravity reaches a point where any motile animal would collapse under its own weight, motility may already cost so much energy it no longer pays for the animal to evolve or maintain motility in a terrestrial environment.

[AFTT47]

Because the luminosity of star declines exponentially with star mass,  the Goldilocks zone around a dwarve star would be in a much steeper part of the parent star's gravity well than the earth is on the sun's.   So any planet in proxima centauri's Goldilocks zone won't be earth like:   It is probably tidal locked to its parent star.  One side is perpetually day, the other perpetually night.

I believe a planet in the Goldilocks zone of most K-type stars (cool, orangish stars typically half the mass of our sun) will probably be tidally locked but there is no question about it with a red dwarf. Perhaps even more significant though, that tidal effect will have all kinds of consequences on the planet's geology. I don't know if it's inevitable that the planet would end up like Jupiter's moon, Io but would think it would have to be allot more active than Earth.