Astronomy miss exoplanet starbursts

Many stars could be more life-friendly than previously thought: potentially devastating radiation outbursts from red dwarf stars tend to occur in their polar regions and thus miss planets, which are often the equator, according to a study. For example, distant worlds could have more atmospheres than previously thought, and thus also provide more conditions for the development of life, astronomers say.

Most of the stars in our galaxy belong to this category, and many of them have been shown to have a planetary system. But to what extent planets around red dwarfs can have life-friendly features similar to those on planet Earth is questionable. Because although these stars are smaller and fainter than our Sun, they are more “hydraphobic”: red dwarfs treat their surroundings with relatively intense bursts of radiation more often than not. These so-called flares are explosions in the atmosphere of stars that throw intense electromagnetic radiation into space. Violent outbreaks are associated with the emission of high-energy particles that can have a devastating effect. It is believed that superplanets can literally push out the atmospheres of planets over time.

Alleged ‘toxic dwarves’ on the horizon

An international team of astronomers has now dedicated a study of this “problematic” activity of red dwarfs from the point of view of astrobiology. Scientists used optical and time-analyzed observations from NASA’s Transiting Exoplanet Survey (TESS) satellite. They first searched archives of data on stars that were particularly well suited to investigation by evaluating the light curves of more than 3,000 red dwarfs. In doing so, they discovered four long-duration flares that were particularly well suited to geographical assignment: 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 they formed.

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Their data analyzes showed that all four flares occurred above about 55 degrees latitude. This indicates that eruptions in red dwarfs usually occur more near the poles than in our Sun, whose flares usually form below 30 degrees latitude. As astronomers assure, the results of only four flares are meaningful: If they are evenly distributed over the surface of the star, the probability of finding four of them at high latitudes would be 1 in 1,000, the team explains.

More possibilities of life

“We thus demonstrated that very large flares from red dwarfs do not flare up at the equator, as they usually do with the Sun,” summarizes first author Ekaterina Eileen of the Leibniz Institute for Astrophysics in Potsdam. “Exoplanets that move on a plane around the star’s equator, such as the planets in our solar system, can therefore be largely protected from such superplanets, as they are pointed up or down outside the exoplanet system. This could improve the prospects for habitability of exoplanets. About little red dwarfs. Otherwise they would be more vulnerable than planets in our solar system due to energetic radiation and particles that go hand in hand with the flares,” says Elaine.

In addition, the results now also shed new light on the properties of the magnetic fields of red dwarf stars, scientists say: The discovery of these polar flares is an additional indication that strong and dynamic concentrations exist near the spin poles. Stars that rotate rapidly in stellar magnetic fields, which can appear as dark spots and flares. “The results tell us something important about how these typically young and young stars generate magnetic fields much stronger than those in our Sun,” says James Davenport of the University of Washington. “This has a huge impact on the way we think about the planets that orbit it,” says the scientist.

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Source: Leibniz Institute for Astrophysics, Potsdam, University of Washington. Articles: Monthly Notices of the Royal Astronomical Society, doi: 10.1093/mnras/stab2159

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