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Planetary protection in the extreme environments of low-mass stars

Published online by Cambridge University Press:  07 August 2014

A. A. Vidotto ,
M. Jardine ,
J. Morin ,
J.-F. Donati ,
P. Lang  and
A. J. B. Russell
A. A. Vidotto
Affiliation:
SUPA, University of St Andrews, North Haugh, KY16 9SS, UK email: [email protected]
M. Jardine
Affiliation:
SUPA, University of St Andrews, North Haugh, KY16 9SS, UK email: [email protected]
J. Morin
Affiliation:
Georg-August-Universität, Friedrich-Hund-Platz 1, D-37077, Goettingen, Germany
J.-F. Donati
Affiliation:
Observatoire Midi-Pirénées, 14 Av. E. Belin, F-31400, Toulouse, France
P. Lang
Affiliation:
SUPA, University of St Andrews, North Haugh, KY16 9SS, UK email: [email protected]
A. J. B. Russell
Affiliation:
SUPA, University of Glasgow, University Avenue, G12 8QQ, Glasgow, UK
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Abstract

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Recent results showed that the magnetic field of M-dwarf (dM) stars, currently the main targets in searches for terrestrial planets, is very different from the solar one, both in topology as well as in intensity. In particular, the magnetised environment surrounding a planet orbiting in the habitable zone (HZ) of dM stars can differ substantially to the one encountered around the Earth. These extreme magnetic fields can compress planetary magnetospheres to such an extent that a significant fraction of the planet's atmosphere may be exposed to erosion by the stellar wind. Using observed surface magnetic maps for a sample of 15 dM stars, we investigate the minimum degree of planetary magnetospheric compression caused by the intense stellar magnetic fields. We show that hypothetical Earth-like planets with similar terrestrial magnetisation (~1 G) orbiting at the inner (outer) edge of the HZ of these stars would present magnetospheres that extend at most up to 6.1 (11.7) planetary radii. To be able to sustain an Earth-sized magnetosphere, the terrestrial planet would either need to orbit significantly farther out than the traditional limits of the HZ; or else, if it were orbiting within the life-bearing region, it would require a minimum magnetic field ranging from a few G to up to a few thousand G.

Keywords

stars: magnetic fieldsstars: planetary systemsstars: rotationastrobiology
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 9 , Symposium S302: Magnetic Fields throughout Stellar Evolution , August 2013 , pp. 237 - 238
Copyright
Copyright © International Astronomical Union 2014 

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