Friday, July 9, 2010

Red dwarfs may be safe havens for extraterrestrial life

The first inhabited exoplanet will revolve around a nearby red dwarf star found in surveys taken within 100 light-years of Earth, it is predicted.

This is so because red dwarfs outnumber sun-like stars and so provide many more targets. And since red dwarfs are dim, planets orbiting them will not be as swamped by starlight making it easier to measure their light.

The planet is expected to be located in the habitable zone around a red dwarf - a sweet spot where liquid water can remain stable on a planet's surface.

A planet in the habitable zone of a red dwarf would complete its racetrack orbit in just two weeks. This would allow multiple transits to be observed quickly. Also, because it is so close to the red dwarf, a planet is more likely to be in an orbit aligned along our line of sight, and will be more likely to be discovered transiting.

However, there is one big catch. Young red dwarfs have a petulant youth stretching over billions of years. Titanic stellar flares erupt without warning and blast out lethal doses of ultraviolet radiation. Ocean life on a planet may be safe from the UV just a few feet underwater and still extract enough light for photosynthesis. But anything living on the surface could get fried without a liberal coating of Sunscreen 2000.

But we now have a glimmer of hope for red dwarf planets. Astrobiologist Antigona Segura of the Universidad Nacional Autsnoma de Mixico (UNAM) in Mexico City, simulated how a 1985 flare from the nearby red dwarf AD Leonis would have affected a hypothetical Earth-like planet orbiting a dwarf, reports Discovery News.e found that UV radiation actually split molecules of oxygen to create more ozone than it destroyed. The simulation made a thicker ozone layer in the planetary atmosphere such that the surface experienced no more radiation than is typical on a sunny day on Earth.

What's more, as the dwarf settles down to a quiescent existence, there would be very little ultraviolet light and an UV filtering ozone layer would not even be needed.

To be sure, there are other oddball characteristics to worry about. Potentially habitable red dwarf planets may keep one hemisphere locked onto their star due to gravitational tidal forces. The resulting slow rotation may give them anaemic magnetic fields that do not block cosmic rays effectively.

But the best solution is to simply go looking. The light-gathering power of the James Webb Space Telescope, slated for a 2014 lauch, would be used to spectroscopically 'sniff' out the exoplanet's atmosphere for chemistry that might be a by-product of organisms on the surface. If we get lucky, and these planets do develop a natural UV shield, then the discovery of an inhabited world may be no more than a decade away.