We report the detection of a strong, organized magnetic field in the secondary component of the massive binary system HD 47129 (Plaskett’s star). Eight independent Stokes V observations were acquiredin the context of the MiMeS (Magnetism in Massive Stars) survey using the spectropolarimeters at the Canada-France-Hawaii Telescope and the Telescope Bernard Lyot.


Artist impression of a magnetic star, credit ESO

The longitudinal field of the secondary is variable implying a minimum surface dipole polar strength of nearly 3 kilo Gauss.  In contrast, we derive an 3 sigma upper limit to the primary’s surface magnetic field of only 0.2 kilo Gauss.

This discovery is raising questions about the origin of magnetism in massive stars and what the potential role of binary interaction in the generation or amplification of such fields.



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