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How are planets orbiting red dwarfs habitable – the most common type of star in the galaxy?



Barnard's red dwarf

This artist’s illustration depicts old red dwarfs such as Barnard’s Star (right) and orbiting rocky planets (left). Credit: NASA / CXC / M. Weiss.

  • How hospitable is the red dwarf, the most common and long-lived star in our galaxy?
  • The researchers used Chandra and Hubble data to determine the severity and frequency of high-energy explosions from nearby red dwarfs.
  • Barnard’s Star is one of the closest to Earth at just six light years.
  • At 10 billion years, Barnard’s Star is still extremely active and could destroy the atmosphere of any planets orbiting it.

A research study using data from NASAChandra Observatory and Hubble space telescope It provides new insights into an important question: How about planets orbiting the most common stars in the galaxy? The goal of the new study is Barnard’s Star, one of the closest to Earth at a distance of just six light years.Barnard’s Star is a red dwarf, a tiny star that slowly burns through a fuel supply and can outlast stars. Medium, like our sun, is about 10 billion years old, making it twice as old as our sun.

The authors used Barnard’s Star as a case study to learn how flare from an old red dwarf might affect the planets orbiting that star. The artist’s illustration at the top of this page shows an old red dwarf, such as Barnard’s Star (right) and orbiting rocky planets (left).

Barnard's Starlight Curve

Credit: X-ray light curve: NASA / CXC / University of Colorado / K. France et al; UV light curve: NASA / STScI;

Barnard’s star research team’s Chandra observations, taken in June 2019, found one X-ray light and their Hubble observations taken in March 2019 revealed an energy flare. High, ultraviolet two eyes (Shown in the image above) Both observations were approximately seven hours long, and both plots show the brightness of X-rays or ultraviolet rays extending down to zero. Based on the length of the fireworks and observations, the authors conclude that Barnard’s star emits potentially devastating flares about 25% of the time.

The team then studied what these results mean for rocky planets orbiting in habitable regions where liquid water can exist on their surface around old red dwarfs such as Barnard’s star. Any atmosphere that formed early in the life of a planet in the habitable zone is likely to be eroded by high-energy radiation from the star in its youth. Later, however, the planet’s atmospheres may re-emerge as the stars become less active as they age. This regeneration process can be carried out by gases released as a result of solid material or gas released by volcanic processes.

However, a powerful flare attack like the one reported here, which has been repeated over hundreds of millions of years, could erode the atmosphere that was reconstructed on rocky planets in habitable zones. The illustration shows the atmosphere of a rocky planet being swept to the left by powerful radiation from the flames produced by a red dwarf. This will reduce the likelihood that these worlds will support life. The team is studying high-energy radiation from many red dwarfs to determine whether Barnard’s star is normal.

Reference: “High Energy Radiation Environment Around 10 Gyr M Dwarfs: Finally Live?” By Kevin France, Girish Duvvuri, Hilary Egan, Tommi Koskinen, David J. Wilson, Allison Youngblood, Cynthia S. Froning, Alexander Brown. , Julián D.Alvarado-Gómez, Zachory K.Berta-Thompson, Jeremy J.Drake, Cecilia Garraffo, Lisa Kaltenegger, Adam F. Kowalski, Jeffrey L. Linsky, RO Parke Loyd, Pablo JD Mauas, Yamila Miguel, J.Sebastian. Pineda, Sarah Rugheimer, P.Christian Schneider, Feng Tian, ​​and Mariela Vieytes October 30, 2020. Astronomical Journal.
DOI: 10.3847 / 1538-3881 / abb465

A paper describing these results, led by Kevin France of the University of Colorado at Boulder, appears in the Oct. 30, 2020 issue. Astronomical JournalNASA’s Marshall Space Flight Center manages the Chandra program. The Chandra Center of the Smithsonian Astrophysics Observatory controls scientific and aeronautical operations from Cambridge and Burlington, Massachusetts.




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