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A superflare in Proxima Centauri conditions the habitability of the closest exoplanet to Earth

Octavi Fors and Daniel del Ser ICCUB researchers.

Octavi Fors and Daniel del Ser ICCUB researchers.

The flare shown in the sequence of Evryscope images. The highest peak of the superflare was 35x brighter; over shorter timescales relevant for the human eye, Proxima was 70x brighter, just visible to the naked eye at dark sites.

The flare shown in the sequence of Evryscope images. The highest peak of the superflare was 35x brighter; over shorter timescales relevant for the human eye, Proxima was 70x brighter, just visible to the naked eye at dark sites.

02/07/2018

Recerca

A team of researchers from the Institute of Cosmos Sciences of the UB (ICCUB), the University of North Carolina at Chapel Hill (UNC-CH, USA), and the Royal Academy of Sciences and Arts of Barcelona (RACAB), detected the first naked-eye solar superflare in Proxima Centauri, the closest star to the Sun. The obtained results limit the habitability of the Proxima b exoplanet, orbited by this star.

A solar flare is a phenomenon causing an increase in the brightness of a star due its magnetic activity. For Proxima Centauri, another star activating the Sun, these flares emit lethal amounts of UV radiation and charged particles, such as protons, that can destroy the ozone (O3) of Proxima b’s atmosphere. This research study, published in the journal The Astrophysical Journal Letters, states that “the temporary distribution of these solar super flares takes place at least about five times per year, which means the 90 % of the O3 of Proxima b would disappear in five years, and the rest would be removed at scales of 100,000 years”, says Octavi Fors (ICCUB, UCN-CH, RACAB), one of the authors of the study.

“Since Proxima b does not have O3 , and the UV radiation level is about a hundred times more intense than the one the most resistant microorganism can bear,  the kind of life in the surface of the planet is very limited. This would suit only extremely UV radiation-resistant organisms”, says Daniel del Ser (ICCUB, UNC-CH, RACAB), co-author of the study. “In fact –the researcher continues- those ways of life that are not protected under a surface (such an ocean) would hardly survive in a planet that is exposed to these kind of violent ultraviolet emissions”. 

Data obtained from the Evryscope telescope, which conducts observations on the entire visible sky every two minutes. This solar super flare was observed in March 2016, when Proxima Centauri was seventy times brighter and therefore was easily seen.

At the same time the Evryscope observations were conducted, the HARPS high resolution spectrograph analysed the visible spectrum of the solar flare to determine, among other reasons, the existence of a coronal mass ejection. Also, the photochemical effects of the atmospheric compounds produced by the extreme stellar activity were modelled.   

Article reference:

Ward S. Howard, Matt A. Tilley, Hank Corbett, Allison Youngblood, R. O. Parke Loyd, Jeffrey K. Ratzloff, Nicholas M. Law, Octavi Fors, Daniel del Ser, Evgenya L. Shkolnik, Carl Ziegler, Erin E. Goeke, Aaron D. Pietraallo, Joshua Haislip. “The first naked-eye superflare detected from Proxima Centauri”. The Astrophysical Journal Letters, 860:L30, June, 2018.

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