Astronomers discover that their flares spit out more far-ultraviolet radiation than previously assumed.

Planets floating within the habitable zone around red dwarfs have little chance to sustain life, because the far-ultraviolet radiation (fUVR) carried by those stars’ flares is too strong for the atmosphere to hold, sterilizing de facto the surface of planets.

This is the conclusion of a group of current and former astronomers at the University of Hawaiʻi Institute for Astronomy who analyzed the archival data from the GALEX space telescope to search for flares among 300,000 nearby stars, publishing their findings in the Monthly Notices of the Royal Astronomical Society.

The discovery suggests that the intense fUVR from red dwarfs’ flares has a significant impact on planets around those stars, rendering eventual exoplanets non-habitable. Interestingly enough though, many exoplanets discovered so far circle around small stars, red dwarfs.

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“Few stars have been thought to generate enough ultraviolet radiation through flares to impact planet habitability.

Our findings show that many more stars may have this capability,” said first author Vera Berger, who led the research, was quoted as saying in a statement released by the University of Hawai’i.

GALEX is now a decommissioned NASA mission that observed most of the sky at near-and far-ultraviolet wavelengths between 2003 and 2013, allowing the team to extract the data for analysis using modern computing.

Upon completion of this work, the researchers concluded that ultraviolet radiation from stellar flares emitted by red dwarfs is three to 12 times more powerful than previously assumed. It can either wipe out planetary atmospheres, threatening their potential to support life, or contribute to the formation of RNA building blocks, which are essential for the creation of life, or both.

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“A change of three is the same as the difference in ultraviolet in the summer from Anchorage, Alaska to Honolulu, where unprotected skin can get a sunburn in less than 10 minutes,” Benjamin J. Shappee, an associate astronomer at the institute and co-author of the study, was quoted as saying.

It is not clear what causes a stronger fUVR, though the team speculates it might be related to the concentration of radiation at specific wavelengths and the presence of carbon and nitrogen atoms.

As more research is needed to mine for full answers, this study nonetheless has greatly updated scientists’ understanding about the environment around stars less massive than our Sun, which emit very little ultraviolet light outside of flares.

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