One of the most powerful flares in our galaxy erupts from star next door

For a brief moment, the dim red dwarf star Proxima Centauri burned thousands of times brighter with ultraviolet radiation.

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Eric Mack
3 min read

Artist's conception of a violent flare erupting from the star Proxima Centauri.

Credit: NRAO/S. Dagnello

Astronomers around the world have spotted one of the most powerful stellar flares ever seen in our galaxy exploding off Proxima Centauri, our nearest neighboring star. 

"The star went from normal to 14,000 times brighter when seen in ultraviolet wavelengths over the span of a few seconds," explains astrophysics assistant professor Meredith MacGregor of the University of Colorado-Boulder, in a statement. MacGregor also led a study on the record-breaking event that was published Wednesday in The Astrophysical Journal Letters.

The flare is not just one of the biggest seen in the Milky Way and the largest recorded from Proxima Centauri (ironically, a relatively small red dwarf star) -- it was about a hundred times more powerful than any flare ever seen from our own sun.

And yet, the whole event lasted only seven seconds and produced very little visible light. Instead, the scientists recorded a huge surge in ultraviolet and millimeter wave radiation.

"In the past, we didn't know that stars could flare in the millimeter range, so this is the first time we have gone looking for millimeter flares," MacGregor said.

Observing the flare was something of an astronomical triumph in itself because it required the coordination of nine different instruments, including the Hubble Space Telescope, the Atacama Large Millimeter Array and NASA's Transiting Exoplanet Survey Satellite, all aimed at the star over the same 40-hour period in 2019. Five of the nine captured the huge flare on May 1, 2019.

In 2016 astronomers discovered an exoplanet orbiting Proxima Centauri in the star's habitable zone, but the frequency of flares from the star, especially blasts this massive, put the odds of habitability in serious doubt.

"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, adding that anything actually managing to live in that system would have to be very different from organisms on Earth.

Co-author Parke Loyd from Arizona State University notes that there are some animals, like jumping spiders, that can see ultraviolet light like that produced by the flare.

"Imagining we could see ultraviolet light and we were standing on the planet Proxima Centauri b when this flare happened, we would have experienced a blinding flash, just about at the limit of our visual range. If organisms do exist on a planet like this, I suspect they would have to react very quickly to protect themselves at the earliest indication of a flare, and they would need to do this several times per day."

While the stellar tumult in our galactic neighborhood might be bad news for the odds of finding familiar life forms there, it suggests there is more to learn about how other stars behave.

"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.

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