No More Hope for 'Second Earth'? Massive Solar Flare Scorched Exoplanet Last Year, Say Astronomers
Mars may have giant dust storms, huge temperature changes, and a lot of surface radiation, but it may turn out to be a better target for colonization than Proxima Centauri b, the supposed 'second earth' announced in 2016. There was a huge fanfare over the little planet, which orbits the star closest to our own solar system—Proxima Centauri, about 4 light-years away.
The planet appeared to orbit its star in the 'Goldilocks zone,' making it just the right temperature to support life and possess liquid water. There was even speculation that it was a habitable "ocean world," with giant seas sloshing around on its surface.
Turns out that's probably not the case.
According to a new study published in Astrophysical Journal Letters, Proxima Centauri released a massive stellar flare last March that bathed Centauri b in ionizing radiation. The star became about 1,000 times brighter than normal over the course of about 10 seconds, making its flare about ten times brighter than those of our own sun.
"Stellar flares happen when a shift in the star's magnetic field accelerates electrons to speeds approaching that of light," explains Phys.org. "The accelerated electrons interact with the highly charged plasma that makes up most of the star, causing an eruption that produces emission across the entire electromagnetic spectrum."
According to the study, the flare that happened last March may be a relatively common occurrence for the Proxima Centauri system, meaning that any life (or atmosphere) that may have existed on Centauri b was probably annihilated. According to the lead author on the paper, Meredith MacGregor:
"Over the billions of years since Proxima b formed, flares like this one could have evaporated any atmosphere or ocean and sterilized the surface, suggesting that habitability may involve more than just being the right distance from the host star to have liquid water."
But that's not the end of the gloomy news for aspiring space colonists and extraterrestrial enthusiasts. A previous study explained the change in Proxima Centauri's brightness this past March by hypothesizing that giant dust clouds were moving in front of the star, dimming it temporarily. The existence of these dust clouds would have suggested that more planets had formed around the star, providing hope that these other planets might contain life or habitable conditions, even if Centauri b did not. The recognition that the change in brightness was actually a giant, deadly stellar flare, however, makes the dust cloud theory (and more planets in the system) unlikely.