Magazine article Science News

Life Might like Cool Stars' Rocky Planets: Atmospheric Heating Could Evade Tidal Locking, Aid Habitability

Magazine article Science News

Life Might like Cool Stars' Rocky Planets: Atmospheric Heating Could Evade Tidal Locking, Aid Habitability

Article excerpt

There may be more Earthlike environments in the universe than previously thought. Warm, rocky planets that orbit close to their stars might not end up with one side in perpetual daylight as suspected, allowing such planets to sustain an environment hospitable to life.

For the first time, researchers have shown that the gentle tug of a star's gravity on a thin atmosphere can keep a planet spinning even when other forces threaten to slow it down. While planetary scientists have long suspected that this process keeps Venus slowly turning, the mechanism could also work on a planet without Venus' massive atmosphere, Jeremy Leconte, an astrophysicist at the University of Toronto, and colleagues report online January 15 in Science.

Most stars in the galaxy are M dwarfs, red stars that are smaller and dimmer than the sun. Because these stars are relatively cool, their habitable zones--the region around a star where liquid water could, in principle, survive on a planet's surface--are narrow. Planets have to huddle up close to the star to stay warm. For planets so close, the star's gravity slows down their spin so that one side always faces the star, a circumstance known as tidal locking. Climate on a locked planet might be too harsh for life. Dayside warmth could blow ferocious winds; all the water might be ice on the nightside.

Leconte and colleagues used computer simulations to determine that heat in a planet's atmosphere may prevent tidal locking. …

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