From the paper on arXiv.org: "planets that show significant eccentricities – possibly like GL 581 d – are unlikely to become locked in a 1:1-resonance. Therefore, GL 581 d is not considered to rotate synchronously in this study." I'm actually disappointed in the reporter here... that took me all of 30 seconds to find in the original paper. --see edit
Following up on some of the references, it does seem like the long-standing belief is that being a certain distance from the parent star strongly predisposes a planet to tidal locking: "planets close enough to their parent star to possess liquid water on their surfaces (the conventional HZ, below) should be tidally locked (Dole, 1964)," (Scalo et al, 2007); "For stellar masses below 0.6 MSun, exoplanets orbiting in the HZ become tidally locked within the first billion years (e.g., Kasting et al., 1993; Grießmeier et al., 2004, 2005)." (Lammer et al, 2007).
EDIT: D'oh! The OP is talking about 581 g, not d. Serves me right to just grab the first article I see on arXiv about a planet in the Gliese 581 system.
which gives a timescale for how long it takes for a body to become tidally locked to the body it orbits. I haven't plugged in the numbers for this planet, but I'm gonna assume it winds up being much shorter than the age of the star.
Comments
This all seems dependent on the planet being tidally locked. How do they know that? Does a certain distance from the sun absolutely guarantee it?
From the paper on arXiv.org: "planets that show significant eccentricities – possibly like GL 581 d – are unlikely to become locked in a 1:1-resonance. Therefore, GL 581 d is not considered to rotate synchronously in this study." I'm actually disappointed in the reporter here... that took me all of 30 seconds to find in the original paper. --see edit
Following up on some of the references, it does seem like the long-standing belief is that being a certain distance from the parent star strongly predisposes a planet to tidal locking: "planets close enough to their parent star to possess liquid water on their surfaces (the conventional HZ, below) should be tidally locked (Dole, 1964)," (Scalo et al, 2007); "For stellar masses below 0.6 MSun, exoplanets orbiting in the HZ become tidally locked within the first billion years (e.g., Kasting et al., 1993; Grießmeier et al., 2004, 2005)." (Lammer et al, 2007).
EDIT: D'oh! The OP is talking about 581 g, not d. Serves me right to just grab the first article I see on arXiv about a planet in the Gliese 581 system.
Check out the equation towards the bottom of
http://en.wikipedia.org/wiki/Tidal_locking
which gives a timescale for how long it takes for a body to become tidally locked to the body it orbits. I haven't plugged in the numbers for this planet, but I'm gonna assume it winds up being much shorter than the age of the star.
Well, the link you're giving says (at the bottom)
"Gliese 581 g may be tidally locked to its parent star Gliese 581"
So it's not known for certain.
Certain tidal force being exerted I think, it would be a combination of distance and the mass of the star.
That doesn't say much. How can you know for sure that such a planet will be tidally locked? At low orbital radii, you even get relativistic effects:
http://en.wikipedia.org/wiki/Tests_of_general_relativity#Per...