Using the Australian Square Kilometer 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 flash of light ever of Proxima Centauri, the Sun’s closest stellar neighbor and one of the most studied low-mass stars.
An artist’s view of a violent stellar eruption of Proxima Centauri. Image credit: S. Dagnello, NRAO / AUI / NSF.
Proxima Centauri, the smallest member of the Alpha Centauri system, is an M5.5 star located 4,244 light-years away in the southern constellation of Centaurus.
The star has a measured radius of 14% of the Sun’s radius, a mass of about 12% solar energy, and an effective temperature of only about 3,050 K (2,777 degrees Celsius or 5,031 degrees Fahrenheit).
Proxima Centauri is 1000 times less luminous than the sun, making it invisible to the naked eye even at close range.
“Proxima Centauri is a red dwarf, the name for a class of stars that are unusually small and faint,” said Meredith MacGregor, an astrophysicist in the Department of Astrophysical and Planetary Sciences at the University of Colorado, Boulder.
In a campaign spanning several months, Dr. MacGregor and his colleagues Proxima Centauri using ground and space telescopes.
They discovered an extreme flare event on May 1, 2019 with five telescopes tracking its timing and energy in unprecedented detail.
“Now we know that these very different observatories operating at very different wavelengths can observe 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 solar flare lasted only 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 observed in ultraviolet wavelengths in a matter of seconds,” said Dr. MacGregor.
“In the past, we didn’t know that stars could shine in the millimeter range, so this is the first time we’ve been looking for millimeter flames.”
“Those millimeter signals can help researchers gather more information about how stars generate flares.”
In all, the torch was about 100 times more powerful than any comparable torch seen from our sun.
“The planets of Proxima Centauri are hit by something like this not once in a century, but at least once a day, if not several times a day,” said Dr. MacGregor.
“There will probably be more weird kinds of torches that demonstrate different kinds of physics that we haven’t thought of before.”
The findings are published in the Astrophysical Journal Letters.
_____
Meredith A. MacGregor et al. 2021. Discovery of an extremely short flare of Proxima Centauri with millimeter to far ultraviolet observations. ApJL 911, L25; doi: 10.3847 / 2041-8213 / abf14c