Incidence of superflares on Sun-like stars

Solar flares are the most energetic explosions in the solar atmosphere, and similar flares occur on many stars. 'Superflares' many thousands of times more energetic than the average solar flare have been observed from a variety of stars, but the relatively small number observed on solar-type stars has hitherto precluded a detailed study of them. Now, on the basis of an analysis of data from the Kepler satellite, Maehara et al. report observations of 365 superflares, including 101 from slowly rotating solar-type stars, from a sample of around 83,000 stars observed over 120 days. The data suggest that superflares occur more frequently on rapidly rotating stars and on stars with 'starspots' much larger than the sunspots with which we are familiar. There is no historical record of superflares on the Sun in the past 2,000 years, and it is probable that none has occurred in the past one billion years. Bradley Schaefer discusses these findings in an accompanying News and Views, and concludes that it is extremely unlikely that the Sun will host a superflare.