The catalogue of extrasolar planets is growing continuously, containing more than 200 objects, and the detection of these exoplanets has almost become a routine. However, what are the characteristics of the stellar hosts, how can we explain the formation of these planetary systems, or why are some of these giant exoplanets, which are called ‘hot jupiters’, migrating down to very close-in orbits?
An international team of researchers has just discovered a magnetic field on tau Bootis, a star orbited by a giant planet again on a close-in orbit: the first ever detection of this kind, using the ESPaDOnS spectropolarimeter1 installed on the Canada-France-Hawaii telescope2.
Astrophysicists suspect the magnetic field to play a crucial role in some of these questions. However, although indirect effects of magnetic fields have already been detected on stars hosting giant extrasolar planets, no direct measurement had ever been done until now.
They detected the magnetic field of tau Bootis, a one billion year old star, with one and a half solar masses and located at nearly 50 light years from the Earth. This cool and weakly active star, orbited by a giant planet with 4.4 Jupiter masses on a very close-in orbit at 0.049 AU (i.e. 5% of the Sun-Earth distance), possess a magnetic field of a few gauss, just a little more than the Sun’s, but showing a more complex structure.
The data collected from this study is not sufficient to describe precisely these interactions, but this first measurement is opening new prospects for detailed studies of star-planet systems.
Via: Redorbit
