Magnetospheres in exoplanets

Aline Vidotto, Moira Jardine and Christiane Helling claimed to be the first in detecting a magnetosphere in an exoplanet in 2010 (Meyers, 2011¹). They observed the presence of a bow shock in WASP-12b at a distance 4 times the radius of the planet. For the authors, such distance suggest a magnetosphere in WASP-12b four times is radius "because gaseous pressures alone would not be enough to hold [the stellar wind] off at such a distance" (Meyers, 2011¹).

Yet, this is an assumption not yet replicated, and the team is looking for other candidates to further observe the same phenomenon in different exoplanets. Vidotto et al expect to find magnetopheres of between 1 to 40 times the planetary radius if the exoplanets have magnetic fields like Jupiter (~14G) and their stars have magnetic fields between 1 and 100G (Vidotto, 2010²).

References

1. MEYERS Catherine (2011). Alien world's fast orbit creates shock waves. ScienceNOW, 22 April 2011. ISSN 1947-8062. Retrieved from ScienceNOW on 25 April 2011.

2. VIDOTTO Aline, Moira JARDINE & Christiane HELLING (2010). Exoplanet magnetic fields and bow shocks. Royal Astronomical Society's National Astronomy Meeting, 17-21 April 2011, record 194 of 382.

Want to know more?

ScienceNOW - Commentary by Meyers: In this ScienceNOW page you can read the commentary by Meyers, which is, perhaps, a bit more explicit than the abstract published by the Royal Aeronautical Society.
Wiki of Science - WASP-12b magnetic field: This Wiki of Science page summarizes Vidotto's data.
Wikipedia - Bow shocks: This Wikipedia page explains magnetospheric bow shocks (as they apply to Earth) and other bow shocks in the universe a bit further.