A team of astronomers spotted an extreme outburst, or flare, from the Sun’s nearest neighbor–the star Proxima Centauri, a “red dwarf” with about one-eighth the mass of our Sun., Proxima Centauri sits just four light-years, or almost 25 trillion miles, from the center of our Solar System and hosts at least two planets, one of which may look something like Earth. Red dwarfs, also known as M-dwarfs, are a class of stars that contain the least massive and coolest main-sequence stars in the Milky Way. They are also hosts to many of the thousands of known exoplanets.
The most massive red dwarf stars have lifetimes of tens of billions of years, while the smallest have lifetimes of trillions of years. By comparison, the universe is only 13.8 billion years old. These dim red dwarfs will be the last stars shining in the universe. Astrobiologists are intrigued by the possibility of an ancient technological civilization billions of years old on red-dwarf planets. But there’s a deadly catch. The area around M dwarfs likely suffers from intense radiation during their formative years.
In a worldwide campaign carried out over several months, astronomers recentl observed Proxima Centauri using nine ground- and space-based telescopes. They caught an extreme flare on May 1, 2019, with five telescopes that traced its timing and energy in unprecedented detail.
Extraordinary Event in the Span of a Few Seconds
“The star went from normal to 14,000 times brighter when seen in ultraviolet wavelengths over the span of a few seconds,” said MacGregor, about the stellar flare event that occurs when a shift in the star’s magnetic field accelerates electrons to speeds approaching that of light. The accelerated electrons interact with the highly charged plasma that makes up most of the star, causing an eruption that produces emission across the entire electromagnetic spectrum.
“This flare is striking in just how short it is! Most flares that we have previously seen at other wavelengths are much longer, on the order of minutes to hours in duration,” MacGregor told The Daily Galaxy. “Clearly there is a lot more to learn about flaring events on short timescales like this. The typical picture of flares invokes magnetic loops that are twisted up and eventually snap, releasing large amounts of energy. One hypothesis for the short event is that we are seeing a single magnetic loop twist and snap, instead of the chain or ‘arcade’ of many loops twisting and snapping at the same time that has been used to describe longer duration events.”
“Proxima Centauri is of similar age to the Sun, so it’s been blasting its planets with high energy flares for billions of years,” said Alycia Weinberger at the Carnegie Institute of Science. “Studying these extreme flares with multiple observatories lets us understand what its planets have endured and how they might have changed.”
“If there was life on the planet nearest to Proxima Centauri, it would have to look very different than anything on Earth,” MacGregor said. “A human being on this planet would have a bad time.”
“A Coup in Astrophysics”–Nine Observatories Involved
To see just how much Proxima Centauri flares, the researchers pulled off what approaches a coup in the field of astrophysics: They pointed nine different instruments at the star for 40 hours over the course of several months in 2019. Those eyes included the the duPont Telescope at Carnegie’s Las Campanas Observatory in Chile, the Hubble Space Telescope, the Atacama Large Millimeter Array (ALMA), and NASA’s Transiting Exoplanet Survey Satellite (TESS). Five of them recorded the massive May 1 flare from Proxima Centauri, capturing the event as it produced a wide spectrum of radiation. This marked the first time astronomers have ever had this kind of multi-wavelength coverage of a stellar flare.
“Now we know these very different observatories operating at very different wavelengths can see the same fast, energetic impulse,” Weinberger said.
In-Depth Anatomy of a Flare
The technique delivered one of the most in-depth anatomies of a flare from any star in the galaxy. While it didn’t produce a lot of visible light, it generated a huge surge in both ultraviolet and radio, or “millimeter,” radiation. These signals could help researchers gather more information about how stars generate flares.
They also suggest that there may be more surprises in store from the Sun’s “next door” neighbor.. Going forward, “there will probably be even more weird types of flares that demonstrate different types of physics that we haven’t thought about before,” MacGregor concluded.
Source: Meredith A. MacGregor et al. Discovery of an Extremely Short Duration Flare from Proxima Centauri Using Millimeter through Far-ultraviolet Observations. The Astrophysical Journal Letters, Volume 911, Number 2 Published 2021 April 21.
Image shown at the top of the page is an artist’s conception of the violent stellar flare from Proxima Centauri discovered by scientists in 2019 using nine telescopes across the electromagnetic spectrum, including the Atacama 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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