Apr 132018

Proxima Centuri, as has been know for a few years now, has a roughly Earth-sized planet in it’s habitable zone. Yay! But… Proxima is a red dwarf. Worse, it’s a red dwarf with some serious flare activity. Since it is so small and dim, the habitable zone is *real* close to the star, which means that flares can do some serious damage to planeary atmospheres. How bad are Proximas flares? Well…

Proxima Centauri just released a flare so powerful it was visible to the unaided eye

“In March 2016 the Evryscope detected the first-known Proxima superflare. The superflare had a bolometric energy of 10^33.5 erg, ~10× larger than any previously-detected flare from Proxima, and 30×larger than any optically measured Proxima flare. The event briefly increased Proxima’s visible-light emission by a factor of 38× averaged over the Evryscope’s 2-minute cadence, or ~68× at the cadence of the human eye. Although no M-dwarfs are usually visible to the naked-eye, Proxima briefly became a magnitude-6.8 star during this superflare, visible to dark-site naked-eye observers.”


When a flare is 68 times brighter than the rest of the star… that means you have some variability issues. An earth-like world around Proxima is *real* unlikely. Assume that one – let’s say Earth – was suddenly miracled into existence smack in the middle of the habitable zone. You’re going about your day when there is a sudden “BING” sound, and the quality of the sunlight suddenly changes. Not quite as bright, a bit redder (almost like a really powerful incandescent bulb), but just as warm. You look at the sky. It had been a nice bright blue; now its a darker, less happy blue, leaning a bit purplish and gray. You look at the sun and it hits you: “hey, that ain’t right.” It’s the wrong size… visually much bigger. You can almost look at it with just sunglasses. When you do, it looks blotchy.

But you’re not a terribly jittery person. Things looks slightly different, but everything seems to still be functioning, so who cares.

And then SURPRISE FLARE. The sunlight gets ~70 times brighter for a few minutes. Anything flammable flamms. The road melts. You go blind. A portion of the atmosphere says “screw this noise” and blows off into space; there is a  slight but measurable permanent decrease in atmospheric pressure even after all the CO2 from the fires settles out.

 Posted by at 10:43 pm
  • Herp McDerp

    A deep-ocean world — a “warm super-Europa” — might harbor a biosphere that could survive the flares. I wouldn’t want to live there, though.

    • Scottlowther

      I can’t be bothered to do the math, but I suspect such a place would not last geological timespans. Each flare might not penetrate meaningfully into the oceans, but it would flay the atmosphere. The ocean would outgas enough to keep the pressure comfy, but over time the ocean would get eaten away.