Anatomy of the Superflare of Proxima Centauri (Planetary Science)

It was a record flare, the one observed on the star closest to the Solar System on May 1, 2019. Record for power, about a hundred times higher than that of flares produced by the Sun. And record for amount of information collected thanks to multiband data, from X radio, acquired through five space and ground-based telescopes

It lasted seven seconds. On Earth it was seen about two years ago, on May 1, 2019. But having originated over 40 thousand billion km from us (therefore just over four light years away), when it happened, here in our part still 2015. We speak of a flare , or blasting . So of an eruption of energy and matter of terrifying power – the energy of billions of bombs . A flare occurred, in this case, not on the Sun but on the star closest to it: Proxima Centauri . It was the largest flare ever recorded on our galactic neighbor – a hundred times more powerful than those produced by the Sun – and one of the most violent ever seen in our entire galaxy.

Proxima centauri is a red dwarf. Its mass is about one eighth of that of the Sun, of which it is the same age. And at least two planets orbit around it , perhaps habitable. One more reason, in addition to being our neighbor, to make it a special sight. And in fact there were nine telescopes – from the ground and from space – that on that day in early May had their eyes on her, as part of an observation campaign that took place over several months in 2019 total of 40 hours. Nine telescopes, five of which recorded the superflash live

“In the space of a few seconds, given the ultraviolet wavelengths, the brightness of the star has increased by 14 thousand times,” recalls Meredith MacGregor of the University of Colorado at Boulder, first author of the study on the phenomenon published this week in The Astrophysical Journal Letters .

An event that certainly does not argue in favor of the presence, in those parts, of any forms of life – even if it lasted only seven seconds. It was also the most powerful, but not the only one, during the 40-hour observation campaign. Scientists estimate that superflars are almost everyday phenomena, for a star like Proxima Centauri. It is then necessary to multiply them for billions of years, to get an idea of the burst of radiation suffered by the planets that surround it.

Artist’s impression of a stellar flare seen from planet Proxima b, a potentially Earth-like world. 
Credits: Nrao / S. Dagnello

“If there ever was any life on the planet closest to Proxima Centauri, it would have to be very different from any other life here on Earth. A human being on that planet would have had a bad time, ”MacGregor observes about the 2019 event.

Stellar flares occur when – following a magnetic reconnection – the star accelerates electrons to speeds approaching that of light. The accelerated electrons interact with the highly charged plasma that makes up the bulk of the star, causing an eruption that produces emissions across the electromagnetic spectrum.

Electromagnetic spectrum that the use of multiple telescopes sensitive to different wavelengths – including Hubble, Tess and Alma – has made it possible to keep an eye on as rarely happens. The multiband approach has thus led to one of the most in-depth analyzes ever conducted on the flares of a star in our galaxy. With some surprising results. Weak in visible light, the flare generated a huge wave of not only ultraviolet but also radio radiation – particularly in the millimeter band, never seen before for a stellar flare .

Featured image: Artist’s impression of a Proxima Centauri flare. The exoplanet Proxima b is depicted in the foreground. Credits: Roberto Molar Candanosa / Carnegie Institution for Science, Nasa / Sdo, Nasa / Jpl


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