Many stars could be more life-friendly than previously thought: The potentially destructive bursts of radiation from the red dwarf stars tend to occur in their polar regions and thus miss the planets, which are mostly circling equatorially, according to a study. For example, the distant worlds could have an atmosphere more often than previously thought and thus also offer more conditions for the development of life, say the astronomers.
Most of the stars in our galaxy belong to this category and many have been shown to have a planetary system. But to what extent planets around red dwarfs can have life-friendly features that are similar to those of our earth is questionable. Because although these stars are smaller and fainter than our sun, they are much more “rabid”: Red dwarfs treat their surroundings comparatively often with intense bursts of radiation. These so-called flares are explosions in the atmospheres of stars that eject intense electromagnetic radiation into space. Violent outbreaks are associated with the emission of high-energy particles that can have a destructive effect. It is believed that superflares can literally blow away the atmospheres of planets over time.
Alleged “poison dwarfs” in their sights
An international team of astronomers has now devoted a study to this “problematic” activity of the red dwarfs from the point of view of astrobiology. The scientists used optical and time-resolved observations from NASA’s Transiting Exoplanet Survey Satellite (TESS). They first looked in the data archives for stars that were particularly suitable for their investigation by evaluating the light curves of over 3,000 red dwarfs. In doing so, they discovered four particularly long-lasting flares that were particularly suitable for geographical allocation: In their method, the researchers use the exact shape of the light curve of each star to determine the latitude of the regions in which it was formed.
Their data analyzes showed that all four flares occurred above about 55 degrees latitude. This suggests that the eruptions in the red dwarfs typically occur much closer to the poles than in our Sun, whose flares usually form below 30 degrees latitude. As the astronomers emphasize, the finding is meaningful with just four flares: If they were evenly distributed over the star’s surface, the probability of finding four of them at such high latitudes would be 1 in 1000, explains the team.
More potential for life
“We have thus proven that extremely large flares from red dwarfs do not ignite at their equator, as is typically the case with the sun,” sums up first author Ekaterina Ilin from the Leibniz Institute for Astrophysics in Potsdam. “Exoplanets that move on a plane around the equator of the star, like the planets in our own solar system, could therefore be largely protected from such superflares, as they are directed upwards or downwards out of the exoplanet system. This could improve the prospects for the habitability of exoplanets around small red dwarfs. Otherwise they would be much more endangered than the planets in our solar system due to the energetic radiation and particles that go hand in hand with the flares, ”says Ilin.
In addition, the results now shed new light on the characteristics of the magnetic fields of the red dwarf stars, say the scientists: The discovery of these polar flares is a further indication that strong and dynamic concentrations are in the vicinity of the rotation poles of rapidly rotating stars of stellar magnetic fields that can manifest as dark spots and flares. “The results tell us something important about how these small, typically young stars generate magnetic fields that are much stronger than those of our sun,” says James Davenport of the University of Washington. “That has a huge impact on how we think about the planets that orbit them,” says the scientist.
Source: Leibniz Institute for Astrophysics Potsdam, University of Washington. Articles: Monthly Notices of the Royal Astronomical Society, doi: 10.1093 / mnras / stab2159