The closest star to the Sun, Proxima Centauri, has released a record-breaking flare – and thanks to a network of nine telescopes on the ground and in space, astronomers were able to capture the extreme event.

The discovery is published in The Astrophysical Journal Letters. Proxima Centauri is about one-eighth the mass of the Sun and is classified as a red dwarf. Stars are prone to the occasional flare, but the one seen by five of the nine telescopes on May 1, 2019, was among the most extreme witnessed.

The Atacama Large Millimeter/submillimeter Array (ALMA) witnessed a brightening of the star by a factor of about a thousand in a matter of seconds observing the star in microwaves. The Hubble space telescope observing it in far-ultraviolet saw something even more extreme at those wavelengths.

“The star went from normal to 14,000 times brighter when seen in ultraviolet wavelengths over the span of a few seconds,” lead author Dr Meredith MacGregor, an assistant professor at the University of Colorado Boulder, said in a statement.

Based on current observations, Proxima Centauri is orbited by two planets Proxima b and Proxima c. Proxima c is a mini-Neptune about seven times as massive as Earth. Proxima b is roughly the size of Earth and it is located around the star’s habitable zone, where liquid water can exist on a planet given the right conditions.

Since Proxima Centauri is smaller than the Sun, the habitable zone is much closer compared to the one in the Solar System. Proxima b orbits its star in just 11 days. Being so close to its star, it experiences stellar winds 2,000 times stronger than what Earth experiences. And the release of a huge amount of energy as stellar flares, such as this, also impacts the possible habitability of the planet.  

“Proxima Centauri is of similar age to the Sun, so it’s been blasting its planets with high energy flares for billions of years,” Dr Alycia Weinberger, from the Carnegie Institution for Science, added. “Studying these extreme flares with multiple observatories lets us understand what its planets have endured and how they might have changed.”

ALMA and Hubble were helped in the observations by the Australian Square Kilometre Array Pathfinder (ASKAP), NASA’s Transiting Exoplanet Survey Satellite (TESS), and the du Pont Telescope. This is the first time that a flare from a star other than the Sun had received this kind of coverage. Two instruments capturing one is seen as extremely good – this is winning the lottery.

The observation and the many more that will hopefully be captured in the future will provide more insight into flares beyond what we have seen produced by the Sun.