X-rays could sterilise alien planets in otherwise habitable zones

Intense radiation could strip away the ozone layer of Earth-like planets around other stars and render them uninhabitable, according to a new study led by Dr. Eike Guenther of the Thueringer Observatory in Germany.

Dr. Guenther sets out the work in a presentation on 3rd April at the European Week of Astronomy and Space Science in Liverpool.

Astronomers now know of around 4000 planets in orbit around other stars. A handful of these are both Earth-sized and in the habitable zones of the stars they orbit, where the temperature is right for liquid water.

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Credit: NASA/ESA/G. Bacon (STScI)

Artist’s impression of a red dwarf star orbited by an exoplanet.

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In this conceptual animation, X-ray and extreme ultraviolet light from a young red dwarf star cause ions to escape from an exoplanet’s atmosphere. Scientists have developed a model that estimates the oxygen ion escape rate on planets around red dwarfs, which plays an important role in determining an exoplanet’s habitability.

To determine a star’s habitable zone, scientists have traditionally considered how much heat the star emits. Stars more massive than our sun produce more heat and light, so the habitable zone must be farther out. Smaller, cooler stars yield close-in habitable zones.

 

35 light-years out, in the constellation Boötes, a star smaller and cooler than our Sun blasts 95GHz flare emissions 10,000x brighter than our star.

The Atacama Large Millimeter/submillimeter Array (ALMA) has observed "continuously active," storms which would scald communications satellites orbiting any planet and, moreover, prevent biology from evolving.