Using the Australian Square Kilometre Array Pathfinder (ASKAP), the Atacama Large Millimeter/submillimeter Array (ALMA), the NASA/ESA Hubble Space Telescope, NASA’s Transiting Exoplanet Survey Satellite, and the du Pont Telescope, astronomers have observed the largest flare ever recorded from Proxima Centauri, the Sun’s closest stellar neighbor and one of the best-studied low-mass stars.
An artist’s conception of a violent stellar flare from Proxima Centauri. Image credit: S. Dagnello, NRAO / AUI / NSF.
Proxima Centauri, the smallest member of the Alpha Centauri system, is an M5.5-type star located 4.244 light-years away in the southern constellation of Centaurus.
The star has a measured radius of 14% the radius of the Sun, a mass of about 12% solar, and an effective temperature of only around 3,050 K (2,777 degrees Celsius, or 5,031 degrees Fahrenheit).
Proxima Centauri is 1,000 times less luminous than the Sun, which even at its close distance makes it invisible to the naked eye.
“Proxima Centauri is a red dwarf, the name for a class of stars that are unusually petite and dim,” said Meredith MacGregor, an astrophysicist in the Department of Astrophysical and Planetary Sciences at the University of Colorado, Boulder.
In a campaign carried out over several months, Dr. MacGregor and colleagues observed Proxima Centauri using ground- and space-based telescopes.
They discovered an extreme flaring event on May 1, 2019, with five telescopes that traced its timing and energy in unprecedented detail.
“Now we know these very different observatories operating at very different wavelengths can see the same fast, energetic impulse,” said Dr. Alycia Weinberger, an astronomer in the Earth & Planets Laboratory at the Carnegie Institution for Science.
The May 1, 2019 flare lasted just 7 seconds, and is the brightest ever detected in the millimeter and far-ultraviolet wavelengths.
“The star went from normal to 14,000 times brighter when seen in ultraviolet wavelengths over the span of a few seconds,” Dr. MacGregor said.
“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.”
“Those millimeter signals could help researchers gather more information about how stars generate flares.”
In all, the flare was roughly 100 times more powerful than any similar flare seen from our Sun.
“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,” Dr. MacGregor said.
“There will probably be even more weird types of flares that demonstrate different types of physics that we haven’t thought about before.”
The findings were published in the Astrophysical Journal Letters.
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Meredith A. MacGregor et al. 2021. Discovery of an Extremely Short Duration Flare from Proxima Centauri Using Millimeter through Far-ultraviolet Observations. ApJL 911, L25; doi: 10.3847/2041-8213/abf14c
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