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Assess the habitability of planets around old red dwarfs



Assess the habitability of planets around old red dwarfs

Image source: Chandra X-ray Center

A new study using data from NASA’s Chandra X-ray Observatory and the Hubble Space Telescope provides new insights into an important question: How habitable are the planets orbiting the most common stars in the Milky Way? As reported in our press release, the target of this new study is Barnard’s Star, one of the closest stars only 6 light-years away from Earth. Barnard’s star is a red dwarf, a small star that burns slowly in its fuel supply and has a longer life span than medium-sized stars such as the sun. It is about 1

0 billion years old, twice the size of the sun.


Using Barnard’s Star as an example, the authors studied how the flare produced by an old red dwarf star affects any planet orbiting it. The artist’s illustration depicts an old red dwarf like Barnard’s Star (right) and a rocky planet in orbit (left).

The research team’s Chandra observation of Barnard’s Star in June 2019 found an X-ray flare (shown in the inset frame), and their observation of Hubble’s observations in March 2019 found two A UV high-energy flare (shown in another graphic). Both observations are about seven hours long, and both graphs show that X-ray or ultraviolet brightness has dropped to zero. Based on the length of the flares and observations, the authors concluded that Barnard’s Star releases potentially destructive flares approximately 25% of the time.

The research team then studied the implications of these results for rocky planets orbiting habitable regions in habitable regions (where liquid water may be present on the surface), which are located around ancient red dwarfs like Barnard’s Star. Any atmosphere formed during the early life of a planet in a habitable zone may be eroded by the star’s high-energy radiation during its turbulent young star. However, later as stars become less active with age, the planet’s atmosphere may regenerate. This regeneration process may occur due to gas released by solid matter impact or gas released by volcanic processes.

However, as reported here, powerful flare attacks, repeated for hundreds of millions of years, may erode any regenerated atmosphere on rocky planets in habitable regions. This image shows the atmosphere of the rocky planet being swept to the left by high-energy radiation produced by flares from red dwarfs. This will reduce the chance of sustaining life in these worlds. The team is currently studying the high-energy radiation of more red dwarfs to determine whether Barnard’s stars are typical.

Assess the habitability of planets around old red dwarfs

Image source: X-ray light curve: NASA/CXC/University of Colorado/K. France etc.; UV curve: NASA / STScI

A paper describing these results led by Kevin France of the University of Colorado Boulder was published in the October 30, 2020 issue of Acta Astronomy.


Recently discovered planets are not as threatened by stellar flares as originally thought


More information:
Kevin France and others. The high-energy radiation environment around 10 Gyr M dwarfs: will they eventually be habitable? arXiv: 2009.01259 [astro-ph.EP] arxiv.org/abs/2009.01259

Courtesy of Chandra X-ray Center

Citation: Evaluate the habitability of the planets around the old red dwarfs retrieved from https://phys.org/news/2020-10-habitability-planets-red-dwarfs.html on October 30, 2020 (October 2020 30th)

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