Proxima Cen, the nearest star to our solar system, hosts a likely-rocky planet (Proxima b) in its habitable zone (where surface water can be liquid). We observed a “superflare” on March 18 2016, during which Proxima increased in brightness by a factor of ~100X and irradiated its terrestrial planet Proxima b with potentially-lethal doses of UV radiation. A recent study by Ximena Abrevaya et al. has tested the survival of common micro-organisms in lab experiments mimicking conditions during the superflare. They found approximately 1 in 10,000 survived the flare.
We also observed 23 other large flares on Proxima and use these to demonstrate Proxima b experiences 2-5 superflares in a year, in agreement with a previous estimate by Dr. James Davenport using the MOST satellite. In our paper published in the Astrophysical Journal Letters we used this superflare rate to estimate the habitability of Proxima b. We found a 90% loss to an Earth-like planet’s ozone layer in 5 years and estimated a complete collapse of the ozone layer on geologically- short timescales.