In our solar system, solar flares are the largest explosive events and can last from minutes to hours. It is an intense burst of radiation from the release of magnetic energy associated with sunspots.
Superflares, as the name suggests, are 10 to 1,000 times larger than our solar flares. While solar flares don’t threaten us directly as the Earth’s atmosphere shields us from the radiation, these superflares can bathe a planet with a huge amount of ultraviolet light.
These ultraviolet light from giant stellar flares can destroy a planet’s life forms and make it less habitable.
Now researchers from the University of North Carolina at Chapel Hill, for the first time, have measured the temperature of a large sample of superflares from stars and the flares’ likely ultraviolet emissions. This data can help astrobiologists understand how much radiation planets experience during superflares and limit the number of habitable planets that are targets for the upcoming planet-finding missions. Their findings are published in the Astrophysical Journal.
According to Ward S. Howard, the lead author of this study and a doctoral student in the Department of Physics and Astronomy at UNC-Chapel Hill, “We found planets orbiting young stars may experience life-prohibiting levels of UV radiation, although some micro-organisms might survive.”
Previous work has largely focussed on flare temperature and radiation from a handful of superflares from a few stars. Howard and colleagues expanded the study to the largest sample of superflares by making simultaneous observations using the UNC-Chapel Hill Evryscope telescope array and the NASA’s Transiting Exoplanet Survey Satellite (TESS).
The research team discovered a statistical relationship between the size of a superflare and its temperature. Temperature can predict the amount of radiation, which can determine if life can exist on the surface of a planet.
The superflares emit most UV radiation during a rapid peak that lasts only five to fifteen minutes. To ensure multiple measurements are taken during the peak, the team obtained simultaneous observations from Evryscope and TESS at two-minute intervals. The frequency of observations helped the team discover the amount of time superflares can shower the orbiting planet with intense UV radiation.
This is the first time such large samples have been studied. The flares observed have already suggested the TESS Extended Mission discover thousands of exoplanets orbiting the brightest dwarf stars. TESS is now planning more frequent observations of high priority flare stars from the UNC-Chapel Hill sample.
According to co-author and associate professor of physics and astronomy at UNC-Chapel Hill and principal investigator of the Evryscope telescope, Nicholas M. Law, “Longer term these results may inform the choice of planetary systems to be observed by NASA’s James Webb Space Telescope based on the system’s flaring activity.”
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