Astronomers yesterday announced the discovery of a colossal stellar flare. It erupted from the Proxima b’s host star, Proxima Centauri.
Two powerful solar flares erupted in two minutes. The second one was 10 times brighter than any known flare from Earth’s sun. Thus, increasing Proxima Centauri’s brightness by 1,000 times in just 10 seconds and blasting Proxima b with 4,000 times more radiation than Earth receives from a major outburst.
The flare occurred almost one year ago, in March 2017 and lasted two minutes.
The extremely powerful flare blasted the world with high energy radiation and almost certainly not for the first time. Similar flares, the scientists suggest, have probably bombarded Proxima b for possibly billions of years.
“That’s a pretty safe conclusion,” says Meredith MacGregor of the Carnegie Institution for Science. “We observed for only ten hours and caught this one. So you can extrapolate—and imagine these flares might be relatively common.”
Proxima b, with a mass of at least 1.3 times that of Earth, orbits its sun at a distance of about 7.5 million kilometers (4.6 million miles). Thus, completing one “year” in a bit more than 11 days.
The planet orbits in the red dwarf’s habitable zone. However, astronomers already doubted its habitability because of the star’s extreme solar wind and history of flares.
Flares of such magnitude might eventually obliterate a planetary atmosphere, sterilizing the landscape; with no atmosphere, liquid surface water can’t exist.
“This certainly raises questions about possible habitability,” MacGregor says.
A paper last November looked at the same ALMA observations and concluded the average brightness, including the output of the star and the flare, may have been caused by disks of dust and debris circling Proxima Centauri that are similar to the asteroid and Kuiper belts in Earth’s solar system, possibly indicating the presence of additional planets.
But when MacGregor, Weinberger, and their team looked at the data as a function of observing time, the nature of the transient event became clear, according to the Carnegie statement.
“There is now no reason to think that there is a substantial amount of dust around Proxima Cen,” Weinberger said. “Nor is there any information yet that indicates the star has a rich planetary system like ours.”
Thumbnail image: An artist’s rendition of a stellar flare blasting off of Proxima Centauri, which doesn’t bode well for the habitability of the exoplanet Proxima b