We thought flares from a star’s surface could harm life on any nearby planet – but an analysis suggests that even if planets are in close orbit around small stars, they may actually escape being singed.
at the Leibniz Institute for Astrophysics Potsdam in Germany has been studying flares using data captured by NASA’s Transiting Exoplanet Survey Satellite (TESS). She found that the data made it possible to determine the location of giant flares on four M-dwarfs, the most common type of star in the Milky Way galaxy.
These stars are small and “fully convective”, says Ilin, meaning they release heat by circulating material from the core to the surface and back. Because they are small and relatively cool, planets must orbit them closely in order to be warm enough to potentially support life.
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But their convection and rotation together make these stars produce magnetic fields, which in turn produce frequent energetic flares. If these regularly hit closely orbiting planets, it could make them less hospitable to life.
The flares are visible in the TESS data as variations in the brightness of a star, if the star rotates fast enough to alternately show and hide the flare during its lifetime of 12 to 24 hours.
On all four stars, the flares emanated at latitudes of over 55 degrees. This is significant, because it puts the flares far away from each star’s equatorial plane – which is where any orbiting planets are expected to be found.
Ilin presented her findings on 1 July at the .
, an astrobiologist at the Florida Institute of Technology, calls Ilin’s research interesting and solid, but cautions the sample size is still small.
“If it turns out, however, that flares mostly occur at higher latitudes on fully convective M-dwarfs, then it may reduce the likelihood of impact with planets,” he says. “However, even if flares strike planets regularly, there are still many mechanisms that can mitigate damage [to life] – examples include protection offered by hazes, soils, oceans, as well as evolutionary adaptations like UV screening compounds synthesised by organisms.”
Four stars isn’t a large number to base conclusions on, Ilin concedes. But her observations agree with some computer models of convective stars. “I can absolutely not exclude that these stars happen to be very special. But they don’t look special.”
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