The closest exoplanet to Earth just got doused with deadly flares

Enlarge / An artist's impression of the view of the surface of the planet Proxima b orbiting the red dwarf star Proxima Centauri. (credit: ESO/M. Kornmesser)

Amid much excitement in 2016, astronomers revealed the discovery of an Earth-sized planet around the star closest to our Sun, Proxima Centauri. This exoplanet, just 4.2 light years from Earth, was close enough to its red dwarf star that water might well exist on its surface.

Alas, now we know that life probably does not live on the planet, at least not on the surface. In March 2016, astronomers using an array of telescopes known as Evryscope observed a "superflare" 10 times larger than any previous one detected from the red dwarf star. Based upon these observations, and those of other other instruments with spectrographs, the astronomers determined that about five of these superflares occur in a given year.

In an unpublished paper that describes their use of a model for interactions between the flares and a planetary atmosphere, the astronomers suggest such extreme solar activity would reduce the ozone of an Earth-like atmosphere by 90 percent within just five years, with complete depletion occurring within a few hundred thousand years. This means that ultraviolet light observed in the recent superflare reached the surface with 100 times the intensity needed to kill even microbic life that is resistant to UV light.