Free Astronomy Magazine July-August 2021

37 JULY-AUGUST 2021 ASTRO PUBLISHING wavelengths. The event was recorded by five of the nine telescopes in- volved in the study, including the Hubble Space Telescope (HST) in ul- traviolet, and ALMA in millimeter wavelengths. “The star went from normal to 14,000 times brighter when seen in ultravio- let wavelengths over the span of a few seconds,” said MacGregor, adding that similar behavior was captured in millimeter wavelengths by ALMA at the same time. “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,” said MacGregor, adding that the new observations could help researchers gather more information about how stars generate flares, which can have an impact on nearby life. Powerful flares from our Sun are un- common, occurring only a few times in a solar cycle. According to MacGre- gor, that’s not the case on Proxima Centauri. “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,” said MacGregor. The star is prominent in discussions surround- ing the prospect for life around red dwarf stars because of its proximity to Earth, and because it is host to Proxima Centauri b, a planet that re- sides in the star’s habitable zone. “If there was life on the planet near- est to Proxima Centauri, it would have to look very different than any- thing on Earth,” MacGregor said. “A human being on this planet would have a bad time.” Future observations will focus on un- veiling the many secrets behind Prox- ima Centauri’s flares in the hopes of uncovering the internal mechanisms that cause such powerful outbursts. “We want to see what surprises this star has in store for us to help us un- derstand the physics of stellar flar- ing,” said MacGregor. A rtist’s conception of the violent stellar flare from Proxima Centauri discovered by scientists in 2019 using nine tele- scopes across the electromagnetic spectrum, including the Ata- cama Large Millimeter/submillimeter Array (ALMA). Powerful flares eject from Proxima Centauri with regularity, impacting the star’s planets almost daily. [NRAO/S. Dagnello] !

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