In “Tidal heating shrinks the ‘goldilocks zone’” (Nature News, 08 May 2012), Richard A. Lovett reports, “Overlooked factor suggests fewer habitable planets than thought,”
The habitable zone is the orbital region close enough to a star for a planet to have liquid water, but not so close that all of the water evaporates. For our Sun, the zone extends roughly from the inner edge of the orbit of Mars to the outer edge of that of Venus. For smaller, cooler stars, such as M-class dwarfs, the zone can be considerably closer to the star than Mercury is to the Sun. And because close-in planets are easier to spot than more distant ones, such stars have been a major target for planet hunters seeking Earth-like worlds.
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There’s just one problem with finding habitable planets around such stars, says Barnes. Because tidal forces vary dramatically with the distance between a planet and its star, closer orbits also result in massively larger tidal forces.
We were waiting for someone to notice this problem.
See also: Origin of life researcher: Alien life forms will more likely be constructed in laboratory than found in space?