How habitable are planets that orbit the most common type of stars in the Galaxy?
A new study led by Kevin France from the University of Colorado at Boulder provides insights into this important question. The study published in the Astronomical Journal studied Barnard’s Star using the data from NASA’s Chandra X-ray Observatory and the Hubble Space Telescope.
Barnard’s Star is a red dwarf about 10 billion years old. It is one of Earth’s closest stars with just six light-years from Earth. Red dwarfs are small stars that burn through its fuel supply much slower than medium-sized stars like Sun and last much longer.
The researchers used Barnard’s Star to learn how flares from an old red dwarf might affect any planets orbiting it.
Chandra observations of Barnard’s Star taken in June 2019 uncovered one X-ray flare, and Hubble observations taken in March 2019 revealed two high-energy ultraviolet flares (shown in the graphic). Based on the observations, the authors concluded that Barnard’s Star unleashes potentially destructive flares 25% of the time.
On a rocky planet orbiting around the habitable zone of an old red dwarf similar to Barnard’s Star, high-energy radiation would likely erode any atmosphere formed during the planet’s early life. Regeneration of atmosphere might occur again by gases released by the impact of solid materials or by volcanic processes as the star becomes less active with age.
However, bombardment with power flares like the one from Barnard’s Star repeatedly occurring over hundreds of millions of years may erode the regenerated atmosphere and reduce these worlds’ chance of supporting life.
To ascertain if Barnard’s Star is typical, the researchers are currently studying high-energy radiation from many more red dwarfs.
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