# Can we know if an exoplanet has a magnetic field?

The recent discovery of the exoplanet Proxima b gave rise to several questions concerning its habitability and its potential to host life. A major concern is the huge amount of radiation coming from flares emanating from its star. The planet is closer to its star that the Earth to the Sun and the flares seem to be more frequent there than here. Therefore, for this planet to be habitable -or actually inhabited by some life forms- a strong magnetic field is neccesary.

Thus my question: is it possible to find out whether an exoplanet has a magnetic field and, in such a case, measure its strength somehow?

There are certainly many ways to go about detecting a magnetic field on an exoplanet. Many involve studying interactions with the home star. You may have heard of the case of HD 209458 b. Here, Kislyakova et al. (2014) looked at Lyman-$$\alpha$$ absorption around the planet, which was indicative of neutral atoms moving at high velocities. The only model that explained the behavior was a magnetic field with a magnetic moment about that of Jupiter's, interacting with the stellar wind.