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 ofthestars they orbit, where the temperature is right for liquid water.

But manycandidate Earth-sized worlds are in orbit around red dwarf stars, much smaller and cooler than our own. To be in the habitable zone, the planets need to be much closer to their stars than we are to the sun.

The problem, however, is that red dwarfs can produce significant X-ray emission, and often have large flares of radiation and eruptions of particles in so-called coronal mass ejections (CMEs).

To try to assess the risk, Guenther and his collaborators are intensively monitoring low-mass stars where flares might take place.