From Rick Osmon:
Re: Candidate "habitable" planet called most promising yet (Sept. 29): In reading the story about the "habitable planet" around the star Gliese 581, the question of it's being tidally locked to the star seems unsupported, at least within the story. Do you have any further information on how they arrived at this or could you possibly provide direct contact info to the researchers?
(Editor's note: according to astronomers, tidal locking occurs when two orbiting bodies are so close that their gravitational forces create substantial friction within one or both objects. The rotation of an affected body then slows down until the time it takes to rotate once, equals the time it takes to orbit once. As a result this object will always show the same face to the other one, i.e. it is tidally locked. Scientists can estimate the likelihood that a planet is tidally locked to its host star based on its distance therefrom, its mass and other factors. The original paper on Gliese 581g in PDF form may be found here; see also e.g. here or here for futher details on tidal locking in general.)