The stability of the sun's light has probably nourished terrestrial life, but "superflares"—outbursts 10 to 10,000 times stronger than any known solar flare—can arise from stars as warm and massive as our own. Just one superflare could damage the ozone layer and kill off species on an orbiting planet. Now, thanks to 4 months of observations of 83,000 suns by NASA's Kepler spacecraft, astronomers have discovered that 148 of these stars launched a total of 365 superflares. Most of these feisty stars spin fast, intensifying magnetic fields that spawn spots and flares, but one star in six rotates slowly, like the sun. Every superflare-spewing star has spots so huge they cause the starlight to vary as the star turns, the team reports online today in Nature. Thankfully, spots this large don't appear on the sun, suggesting that our star (shown here) is too tame to unleash a superflare that would fry us all.
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