Proxima Centauri's ‘Superflare’ May Have Destroyed Life's Chances On Earth's Closest Exoplanet

Two years ago, scientists detected a super-flare from the Sun’s neighboring star Proxima Centauri. The Red Dwarf, located some 4.25 light years away from our planet, sits at the bottom on the scale of stars, but the eruption baffled scientists, hinting that similar flares may have wiped out life on Earth’s closest exoplanet, if it had any.

Proxima Centauri is believed to host at least one Earth-sized rocky planet, dubbed Proxima b, in the habitable zone — the region where a planet is far enough from its star to have liquid water and bolsters the chances of finding life. But, the thing is even if Proxima b had any life, it might have been destroyed by the occurrence of intense flares, Allison Youngblood, a postdoctoral fellow at NASA's Goddard Space Flight Center, and her team estimated.

The solar flare detected back in 2016 was 10 times larger than previous ones and one of the strongest ever detected from a star this size. It unleashed 316,227 petawatts of energy and grew in brightness by a whopping factor of 68. At this level, even humans on Earth would have seen the faint star shining in the night sky, Popular Mechanics reported.

Using those observations and sophisticated modeling techniques, scientists predict at least five such flares erupt from the small star every year. This could mean serious trouble for Earth’s closest exoplanet and trim down the possibility of microbial life survival on its surface.

According to the astronomers, regular interactions between the flares and planetary atmosphere could drastically affect Proxima b's atmosphere. For a planet similar to Earth, flares of such magnitude would weaken the ozone layer progressively and deplete it by a whopping 90 percent in a matter of five years. And if this goes on for a few hundred thousand years, the ozone layer would be removed completely, leaving the planet unprotected from its star's harmful ultraviolet radiation.

"Then, if another one of these superflares comes along and there is no ozone protection, the UV radiation incident on the planet's surface would kill even the most radiation-resistant organisms," Youngblood said in a journal article preprint.

With that, the astronomers also note that if the atmosphere of the planet survives superflare impacts in the long-run, microscopic organisms will have to undergo complex adaptations to survive on the planet, just like how lichens evolved for extreme environments with features like UV-protecting pigments, ArsTechnica reported. Scientists around the world are working to better understand the impact of stellar flares in distant systems and how they could affect the possibility of life.

The ArXiv.org preprint paper titled “The first naked-eye superflare detected from Proxima Centauri” was made available on April 5 and is set to be published in the AAS Journals.