"Few stars have been thought to generate enough UV 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 while at the University of Hawai'i and is now based at the University of Cambridge.
Berger and her team utilized archival data from the GALEX space telescope, examining flares among 300,000 nearby stars. GALEX, a now-decommissioned NASA mission, observed most of the sky in near- and far-UV wavelengths from 2003 to 2013. The team employed new computational techniques to extract insights from the data.
"Combining modern computer power with gigabytes of decades-old observations allowed us to search for flares on thousands and thousands of nearby stars," said co-author Dr. Michael Tucker from Ohio State University.
Researchers explained that UV radiation from stellar flares could either erode planetary atmospheres, threatening their potential to support life, or contribute to the formation of RNA building blocks essential for life.
The study, published in the Monthly Notices of the Royal Astronomical Society, challenges existing models of stellar flares and exoplanet habitability. It reveals that far-UV emission from flares is, on average, three times more energetic than typically assumed and can reach up to twelve times the expected energy levels.
"A change of three is the same as the difference in UV in the summer from Anchorage, Alaska to Honolulu, where unprotected skin can get a sunburn in less than 10 minutes," said co-author Benjamin J. Shappee from the University of Hawai'i.
The exact cause of this stronger far-UV emission is not yet clear. The team suspects that flare radiation might be concentrated at specific wavelengths, indicating the presence of atoms like carbon and nitrogen.
"This study has changed the picture of the environments around stars less massive than our Sun, which emit very little UV light outside of flares," said co-author Jason Hinkle.
Berger, now a Churchill Scholar at Cambridge, emphasized the need for more data from space telescopes to study the UV light from stars, which is essential for understanding the source of this emission.
"Our work puts a spotlight on the need for further exploration into the effects of stellar flares on exoplanetary environments," said Berger. "Using space telescopes to obtain UV spectra of stars will be crucial for better understanding the origins of this emission."
Research Report:'Stellar flares are far-ultraviolet luminous
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