Flares from ultracool dwarf stars may threaten the habitability on rocky exoplanets

Earth sized exoplanets in orbit around ultracool dwarf stars are the new favorite target for the hunt of extraterrestrial life. A series of recent discoveries, including seven Earth sized exoplanets in orbit around **Trappist-1** suggest that there might be rocky exoplanets in orbit around billions of red dwarf stars. Three of the exoplanets in the Trappist-1 system are in the habitable zone of the host star, with conditions suitable for liquid water to exist on the surface, a pre-requisite for life as we know it on Earth. This is the most common type of star in the universe. [caption id=“attachment_363658” align=“aligncenter” width=“640”]  The Trappist-1 system. Image: Nasa.[/caption] However, frequent solar flares from the host star could be a problem as far as habitability of the exoplanets in orbit around red dwarf stars are concerned. NASA scientists combed through ten years of data collected by the Galaxy Evolution Explorer (GALEX) spacecraft, to spot differences in the brightness of stars. These differences could indicate the frequency and intensity of flares. Even though large flares are rare, a large number of smaller flares could make the conditions on the exoplanets inhospitable to life. [caption id=“attachment_381123” align=“aligncenter” width=“640”]  The GALEX spacecraft[/caption] Scott Fleming of the Space Telescope Science Institute (STScI) in Baltimore asks, “What if planets are constantly bathed by these smaller, but still significant, flares? There could be a cumulative effect.” [caption id=“attachment_354819” align=“aligncenter” width=“640”]  An artist impression of what the surface of Proxima-b could look like, another potentially habitable planet in orbit around a Red Dwarf. Image: ESO/Reuters[/caption] The data showed a wide range of flares, to the extent that the instrument was sensitive to. Even if the intensity and the frequency of the flares are similar to that of the Sun, the planets in orbit closer to the host star can be exposed to more energy from the flares. All the seven worlds in the Trappist-1 system for example, are closer to the host star than Mercury is to the Sun. The **James Webb Space Telescope** to be launched in 2018 will study exoplanets for signs of life, **including the planets in the Trappist-1 system** .