The most common stars in the Milky Way may not be as hospitable to life as previously thought.
Red dwarfs, stars smaller and lighter than our Sun, can blast planets with intense flares of ultraviolet (UV) radiation, significantly reducing the planet’s chances of becoming habitable, according to a new study.
The team of scientists reached this conclusion by analyzing data collected by the now-defunct NASA mission Galaxy Evolution Explorer (GALEX). Launched in April 2003, GALEX scanned the universe in ultraviolet light, searching for flares from about 300,000 nearby stars until it was shut down in 2013.
The study suggests that such harmful flares may be more common than previously suspected, the researchers say. “Very few stars produce enough UV radiation to affect the habitability of planets through flares. Our results suggest that many more stars may have this ability,” says team leader and University of Cambridge researcher Vera Berger. “The company said in a statement.
Using cutting-edge computer technology, the research team processed the GALEX archive data to gain new insights into red dwarfs.
“By combining modern computer power with gigabytes of decades-old observational data, we were able to find thousands of flares from nearby stars,” said team member Michael Tucker from Ohio State University.
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Scientists already knew that there are several ways that high-energy light from stars in the form of ultraviolet light can be lethal to life, including by stripping away planetary atmospheres and breaking down complex molecules that form the building blocks of biology.
The new study challenges what we know about the habitability of exoplanets, or “exoplanets,” by suggesting that current models of star flares underestimate the risk. The team found that the extreme ultraviolet emission from the flares was about three to 12 times more powerful than expected.
“A change of 3 is equivalent to the difference in summer UV radiation from Anchorage, Alaska, to Honolulu, where unprotected skin would sunburn in less than 10 minutes,” said team member Benjamin J. Shappee of the University of Hawaii.
“This study changes the picture of the environment around stars less massive than our sun that emit little ultraviolet light other than flares,” said team member Jason Hinkle, a doctoral student at the University of Hawaii.
The research team is currently not sure what causes the super-intense UV flare emission, but they think it may be focused on a specific wavelength of light. Since elements absorb and emit light at characteristic wavelengths, this could indicate the presence of carbon and nitrogen atoms.
Berger said more space telescope data is needed to pinpoint the source of the ultraviolet emission from these red dwarf flares.
“Our study highlights the need for further exploration of the influence of stellar flares on exoplanetary environments,” he concluded. “Using space telescopes to obtain UV spectra from stars will be important to better understand the origin of this emission.”
The team’s research was published in the journal. Monthly Notices of the Royal Astronomical Society.
