Superflares are less dangerous to exoplanets than previously thought

Superflares, extreme emissions of radiation from stars, have long been thought to be a possible threat to the atmospheres and potential habitability of exoplanets. However, a new study shows that such outbreaks pose only a limited threat to planetary systems, as they are most often directed not towards the planets.

Using observations from the Transiting Exoplanet Survey Satellite (TESS), astronomers from the Potsdam Institute of Astrophysics, Germany, together with colleagues from other countries, studied large superflares occurring in young, small stars. These stars, called “red dwarfs,” have a lower temperature and lower mass than our Sun.

A large number of exoplanets have been discovered around stars of this type. The question is whether these planets can be habitable, since red dwarfs are more active than the Sun and erupt in more frequent and intense flares. Flares are magnetic explosions in the atmospheres of stars that emit large amounts of electromagnetic radiation into space. Large flares are associated with the emission of high-energy particles that can enter the planets orbiting the star, and have a devastating effect on the planet’s atmosphere, even vaporize it.

In a new scientific work, a team led by Ekaterina Ilyina from the Potsdam Astrophysical Institute has developed a new method for determining the location of star spots on the surface of a star. Using this method on a sample of 1000 red dwarf stars observed by the TESS observatory, the researchers were able to find 4 stars to which the method was fully applicable. The analysis showed that all four stars have spots at latitudes above 55 degrees, and this indicates that star spots in red dwarfs are concentrated in the circumpolar regions, and not in the equatorial ones, the authors explained. This conclusion, in turn, suggests that stellar superflares occurring on such red dwarfs will be directed mainly not into the plane of the planetary system, but perpendicular to it – that is, outward, into the surrounding space. If the spots were evenly distributed over the surface of the red dwarf, then the probability of meeting in the case of four randomly selected stars only a configuration with star spots at latitudes above 55 degrees would be no more than 1/1000, the authors explained.

The research is published in the Monthly Notices of the Royal Astronomical Society.

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