Free Astronomy Magazine May-June 2020

13 MAY-JUNE 2020 ASTROBIOLOGY It is, in fact, known that red dwarfs show violent surface activity for several billion years after their birth, an activity that man- ifests itself with frequent flares that pour high-en- ergy UV radiation (in ad- dition to less abundant X-rays) into their surround- ing space, well beyond their habitable zones. As red dwarfs age, explosive activity decreases signifi- cantly but remains, on av- erage, higher than that of the Sun. We know very lit- tle about the atmospheres of planets orbiting red dwarfs, but we can infer that the intense and prolonged stellar radiation can erode them so deeply as to generate a surface environment totally un- suitable for the appearance of life as we know it. We cannot, however, ever rule out the existence of lifeforms able to adapt to those environments inhospitable to us. Among those who support this hypothesis are Lisa Kaltenegger and Jack T. O’Malley- James (Carl Sagan Institute, Cornell Univer- sity, Ithaca NY). For some years now, these two researchers have developed a very tan- talizing hypothesis (published in several ar- ticles in the Monthly Notices of the Royal Astronomical Society ), according to which planets might exist around red dwarfs with lifeforms capable of defending themselves from UV rays that reach the surface, and these defense mechanisms could possibly be used by us to recognize their existence from Earth. When, about 3.9 billion years ago, the processes that led to the appear- ance of life began on our planet, UV fluxes reaching the ground were more intense than those which typically reach the habit- able zones of red dwarfs. Nonetheless, life blossomed. If we add to this that, according to recent studies, UV radiation would be necessary for prebiotic chemistry, the work T he James Webb Space Telescope, slated to launch in March 2021, will be the most pow- erful instrument available in the search from space of biosignatures originating in other planetary systems. [NASA] T he Transiting Exoplanets Survey Satellite, the successor to the Kepler Space Telescope, has the task of dis- covering new candidate Earth- sized planets or- biting the hab- itable zones of their stars. [NASA]