Magnetars are some of the most extreme objects we know about, with magnetic fields so strong that chemistry becomes impossible in their vicinity. They're neutron stars with a superfluid interior that includes charged particles, so it's easy to understand how a magnetic dynamo is maintained to support that magnetic field. But it's a little harder to fully understand what starts the dynamo off in the first place.

The leading idea, which benefits from its simplicity, is that the magnetar inherits its magnetic field from the star that exploded in a supernova to create it. The original magnetic field, when crushed down to match the tiny size of the resulting neutron star, would provide a massive kick to start the magnetar off. There's just one problem with this idea: we haven't spotted any of the highly magnetized precursor stars that this hypothesis requires.

It turns out that we have been observing one for years. It just looked like something completely different, and it took a more careful analysis, published today in Science, to understand what we've been observing.

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[–] [email protected] 3 points 1 year ago

So, my understanding is that we were able to determine the magnetic strength of the star due to the level of polarization (i.e. faraday effect) of the light. The article goes onto say that it is difficult to detect these types of stars because most of them are not in a binary system. The article isn't clear, but does this mean that they could only make this measurement with the light from the binary? Otherwise, why wouldn't we measure the circular polarization of all stars?