December 15, 2015
Astronomers detected a solar flare 10,000 times stronger than those our Sun emits, but coming from a red dwarf star ten times smaller than the Sun. These small stars are estimated to make three quarters of all the stars in our galaxy, possibly in the whole Universe. If further studies show such strong flares are common, then the life around red dwarf stars would have a hard time developing.
Red dwarf stars are small stars that we can’t see with the naked eye in the night’s sky, but it is estimated that three out of four stars in the Milky Way are red dwarfs. Since they are small, they burn their fuel slowly and live longer than stars like Sun. This gives potential life on exoplanets around red dwarfs more time to develop.
A new study, led by Peter Williams of the Harvard-Smithsonian Center for Astrophysics, Cambridge, USA, brings potential bad news for life in star systems with red dwarfs. One such red dwarf was observed with Atacama Large Millimeter/submillimeter Array (ALMA) as it emitted a solar flare 10,000 times brighter than those from Sun.
The red dwarf in question is 35 light-years from Earth, in the constellation Boötes and goes by the name TVLM 513-46546. It rotates very rapidly, once every two hours, creating a magnetic field hundreds of times stronger than Sun’s.
If this is normal for red dwarfs, it’s bad news for potential life on planets around the majority of stars in our galaxy. Since red dwarfs are small and relatively cold, the habitable zone, where the liquid water and thus life can exist, is much closer to one such star. This puts potential life on an exoplanet in harm’s way. The radiation of solar flares would make life difficult, if not impossible, in three quarters of star systems in our galaxy.
The number of red dwarfs and their longevity make them great place to start search for alien life, yet this new piece of information could turn them into one of the least likely places where life can develop.
"If we lived around a star like this one, we wouldn't have any satellite communications. In fact, it might be extremely difficult for life to evolve at all in such a stormy environment," says Williams. "A planet in the habitable zone of a star like this would be buffeted by storms much stronger than those generated by the Sun."
Future studies have a task of finding out what percentage of red dwarfs show similar magnetic fields and solar flare emissions. Based on that, we can reevaluate if red dwarfs are really the best place to look for alien life.