A giant flare that is 100 times more powerful than any flare our sun has ever released has erupted from a nearby star, a new study says.
Proxima Centauri is our sun's nearest stellar neighbor at 4 light-years, or 25 trillion miles, away. It's a small, dim red dwarf star with just an eighth of the sun's mass. And it's orbited by at least two planets, one of which may be Earth-like.
The extreme flare was observed by a global team of astronomers on May 1, 2019, and it only lasted for about seven seconds. The team used five telescopes, both ground and space-based, to capture the moment.
It's the largest flare ever recorded emanating from Proxima Centauri. The flare started near the star's surface and ranks as one of the most violent seen anywhere in the Milky Way galaxy.
The study published Wednesday in The Astrophysical Journal Letters.
"The star went from normal to 14,000 times brighter when seen in ultraviolet wavelengths over the span of a few seconds," said Meredith MacGregor, study author and assistant professor at the University of Colorado Boulder, in a statement.
A planet lashed by radiation
These flares occur when a star experiences a shift in its magnetic field, which accelerates electrons to nearly the speed of light. These speedy electrons interact with charged plasma, which comprises much of the star. This interaction leads to an eruption of varying wavelengths of energy, including radio waves and gamma rays.
And when this much energy is released, the planets orbiting the star face its wrath.
"Proxima Centauri is of similar age to the Sun, so it's been blasting its planets with high energy flares for billions of years," said Alycia Weinberger, study coauthor and staff scientist at the Carnegie Institution for Science, in a statement. "Studying these extreme flares with multiple observatories lets us understand what its planets have endured and how they might have changed."
Red dwarf stars are common in our galaxy, and in recent years, astronomers have discovered they tend to host exoplanets.
"A lot of the exoplanets that we've found so far are around these types of stars," MacGregor said. "But the catch is that they're way more active than our sun. They flare much more frequently and intensely."
Our sun doesn't release many powerful flares; they occur only a few times during each 11-year solar cycle.
However, these flares are much more common on Proxima Centauri. During their observation campaign, the astronomers recorded many other flares produced by the star over the course of 40 hours.
"Proxima Centauri's planets are getting hit by something like this not once in a century, but at least once a day if not several times a day," MacGregor said.
Proxima Centauri has intrigued scientists because research has suggested that the planet nearest the star, Proxima Centauri b, could be potentially habitable.
"If there was life on the planet nearest to Proxima Centauri, it would have to look very different than anything on Earth," MacGregor said. "A human being on this planet would have a bad time."
Over time, these flares could strip away Proxima Centauri b's atmosphere, if it has one, and expose any potential life there to harmful radiation.
However, the radiation released by the flares could also lead to chemical reactions that produce molecules acting as the precursors to life.
Capturing a stellar moment
In order to observe such an extreme flare, researchers pointed nine ground and space-based telescopes at the star for several months in 2019. These included NASA's Hubble Space Telescope and the Transiting Exoplanet Survey Satellite, as well as the Atacama Large Millimeter Array of telescopes and the duPont Telescope at Carnegie's Las Campanas Observatory, both in Chile.
Multiple telescopes were able to capture the event across the spectrum of radiation produced by the flare, making it the first time astronomers have captured the multi-wavelength output of a stellar flare.
"Now we know these very different observatories operating at very different wavelengths can see the same fast, energetic impulse," Weinberger said.
Visible light wasn't actually released by the flare, but huge surges in radio and ultraviolet radiation were in the flare. The observations of the stellar flare could change scientists' understanding of how flares are generated by stars.
Astronomers want to keep observing the star because "there will probably be even more weird types of flares that demonstrate different types of physics that we haven't thought about before," MacGregor said.
Studying these flares could help scientists develop a better sense of where to search for life outside of our solar system.