Under pressure: Extreme atmosphere stripping may limit exoplanets’ habitability

New models of massive stellar eruptions hint at an extra layer of complexity when considering whether an exoplanet may be habitable or not.

Models developed for our own Sun have now been applied to cool stars favored by exoplanet hunters,in research presented by Dr. Christina Kay, of the NASA Goddard Flight Center, on Monday 3rd July at the National Astronomy Meeting at the University of Hull.

Coronal mass ejections (CMEs) are huge explosions of plasma and magnetic field that routinely erupt from the Sun and other stars.

When a CME impacts a planet, it compresses the planet’s magnetosphere, a protective magnetic bubble shielding the planet. Extreme CMEs can exert enough pressure to shrink a magnetosphere so much that it exposes a planet’s atmosphere, which can then be swept away from the planet. This could in turn leave the planetary surface and any potential developing lifeforms exposed to harmful X-rays from the nearby host star.

The results suggest that an exoplanet would need a magnetic field ten to several thousand times that of Earth’s to shield their atmosphere from the cool star’s CMEs. As many as five impacts a day could occur for planets near the ACS, but the rate decreases to one every other day for planets with an inclined orbit.

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