Hot Magnetic Stars

To my understanding, magnetars produce the strongest magnetic fields known to man. Yet, as they are stars, they are ridiculously hot. I thought that after a certain temperature, magnets no longer produced magnetic fields. So how can a star at millions of Kelvin degrees produce such a powerful magnetic field?
- Matthew (age 16)
Tracy, California, USA

Magnets made out of ferromamagnetic materials, things where the little spins can lower their energy by lining up, lose their magnetism when they're hot. The reason is that hot things have enough random therma energy that they don't care all that much about lowering their energy. It's the same reason that ice melts when it's hot, even though the ice form has lower energy than the liquid form.

Those magnetic stars are magnetic for completely different reasons than a permanent magnet. There are some strange non-equilibrium currents. ()  It sounds a little more like the effects that make the Earth a weak magnet, involving heat flow, and not like the simple equilibrium magnetism of a permanent magnet.

Mike W.

(published on 09/02/2015)