Small stars are unpredictably violent, as seen in recent observations of a powerful flare ejected from our nearest neighbor Proxima Centauri that wowed astronomers. Proxima b, a small rocky planet orbiting within the star's "habitable zone," was surely irradiated when the star flared to over 1,000 times its usual brightness in a matter of 10 seconds. Whether life could survive such extreme conditions is unknown.
Why it matters: Proxima b was a tantalizing candidate in the search for life that perhaps has been all but wiped out. Small dwarfs are the most common variety of stars in our galaxy. It's possible that the majority of planets — which we continue to learn are common, too — circle these weak stars. And, we're finding more and more planets in the habitable zones of these red dwarf stars, meaning liquid water could potentially exist on their surfaces. But if they aren't hospitable, the arena to look for viable life may shrink again.
One more thing: If any life arises on a planet like this, they'll have a view quite unfamiliar to us. Their small parent star is less energetic, and instead of emitting bright white light it instead fills their skies with redder hues.
Paul Sutter is a cosmological researcher at Ohio State University's Center for Cosmology and Astro-Particle Physics.