Wednesday, July 07, 2010
Red dwarf stars are the most common stars in the universe (unless one considers brown dwarfs to be stars as well, though technically they're sub-stellar objects) and thus the question of habitability on planets orbiting them is of crucial importance to ascertaining just how common life is. The most well-known article on red dwarfs and habitability is probably this one called Red, Willing and Able from 2001, making the argument that planets around red dwarfs should be able to have life as well. One of the previous issues with planets orbiting these stars is that their habitable zones are located so close to the stars that planets orbiting there will likely be tidally locked, thus having one side continuously facing the star just as our Moon continually faces us. With a proper atmosphere though this shouldn't be a big problem, and especially considering the prospect of life in oceans which would be much less susceptible to conditions on the surface.
However, the big question has always been that of flaring since red dwarf stars for a period of time will usually flare up in ways that stars of the Sun's size do not. The closest star to us (Proxima Centauri) is a flare star, and the next closest star to us after the Alpha Centauri system, Barnard's Star, is a flare star as well. In addition to that the first Earth-like planet in the habitable zone of a star will certainly be around a red dwarf, so resolving the question of whether flaring is dangerous to life on a planet or not is of crucial importance.
That brings us to the study mentioned today: analyzing a flare in 1985 from the nearby red dwarf star AD Leonis, it turns out that it would have created more ozone than it would have destroyed on an Earth-like planet and such a planet would have had an ozone layer imparting no more radiation on the ground than a sunny day here on Earth.