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Somewhere in the universe, there could be organisms capable of surviving things we couldn't even dream about, but some planets are so inhospitable that even a vacationing tardigrade might want to pack its bags and rocket on out of there.
Earth can endure the Sun having tantrums otherwise known as solar flares (above), even though they can mess up signal transmissions. We are too far away to really feel the effects of the searing heat and massive amounts of UV radiation (and get a protection boost from the ozone layer and SPF in a bottle). Some planets are much less fortunate — they might be orbiting their stars in the habitable zone, but these stars burst out in super-flares that can be 10 to 10,000 times more intense than anything the Sun can belch out. That’s about 15700 to 71500 degrees Fahrenheit. There is no sunblock that could possibly save you from that.
Life as we know it would perish on such a planet. For the first time ever, a team of scientists from UNC Chapel Hill have measured these flares to determine the chances of habitability, if there even are any, on planets constantly exposed to super flares. There are at least twice as many of these planets than previously thought. It could save time for planet-hunting telescopes like TESS that are seeking out more habitable worlds. Cooler flares tend to burn orange, but the hottest glow blue.
“Some flares are so hot and so blue they emit most of their energy in the ultra-violet where DNA and cell damage occur and where molecules in Earthlike atmospheres are broken apart,” doctoral student Ward S. Howard, who led a study recently published in The Astrophysical Journal, told SYFY WIRE. “The flare temperature tells you exactly how much energy gets emitted as ultra-violet light.”
Even if an Earthlike planet is orbiting in what should be its star’s habitable zone, frequent super-flares that obliterated its atmosphere mean its habitability factor is just about zero. That doesn't necessarily rule out every possible type of organism. If scientists are speculating that alien microbes could be thriving in the toxic clouds of Venus or the frozen wastelands of Mars, some sort of microorganism might still make it on planets bombarded by super-flares. Life can survive far beyond the surface. Extremophiles on Earth can thrive everywhere from the darkest caves to hydrothermal vents at the bottom of the ocean. Mars barely has any semblance of an atmosphere, which is why the search for any life or at least evidence of extinct life is turning its focus underground.
But what would happen if Earth were suddenly thrown that close to the mouth of the super-flare dragon? These are nothing like solar flares. Maybe we’d get through one after trillions of dollars’ worth of damages to our electrical and telecommunications grids, Howard believes the future would be grim.
“The biggest ones might cause a really bad sunburn, but that's all because of Earth's ozone layer—without the ozone layer such a flare would be lethal,” he said. “That's where repeated flaring comes in. These superflaring stars will destroy planet atmospheres over time, leaving the surface potentially unprotected.”
But wait. What about planets that are so far from the offending star that what causes devastation to nearer planets could possibly unfreeze them? Think of something as far from a super-flaring star as Neptune is from the Sun. It might seem like an opportunity for ice to melt and life to possibly emerge, but Howard believes these planets are much too far from the liquid-water habitable zone for it to make any difference. Even super-flares would not be powerful or frequent enough to morph a frozen planet into an orb of liquid water. However, maybe if something is on the outer edge of the habitable zone, about the distance of Mars, it might have a chance if it already has life hiding from the radiation in its depths, or at least the chemistry necessary for life to spawn.
There is also the possibility of life thriving on the dark side of a tidally locked planet, which always has just one side facing its monster star. Life can adapt to darkness. If there are sightless cave fish that have no problem surviving in the bowels of Earth, there might still be a chance for life on flare-bombed planets to make it where the destructive forces can’t reach.
“The combination of atmosphere loss and surface flux may prevent life from ever getting started on these planets in the first place,” Howard said, “But most Earth-sized planets in the habitable zones of flare stars are tidally locked, so that only one side of the planet ever faces the star. You could imagine a giant plant living on the dark side and reaching tendrils around to the light side and growing new ones after each flare.”
Maybe TESS should go over to the dark side even if this is just speculation. There might not be Sith lords, but there might be alien life-forms.