From Astronomy Magazine:
Scientists using the European Space Agency’s (ESA) XMM-Newton space telescope have discovered that a curious dead star has been hiding one of the strongest magnetic fields in the universe all along, despite earlier suggestions of an unusually low magnetic field.
The object, known as SGR 0418+5729 (SGR 0418), is a magnetar, a particular kind of neutron star.
A neutron star is the dead core of a once massive star that collapsed in on itself after burning up all its fuel and exploding in a dramatic supernova event. They are extraordinarily dense objects, packing more than the mass of our Sun into a sphere only some 12 miles (20 kilometers) across.
A small proportion of neutron stars form and live briefly as magnetars, named for their extremely intense magnetic fields, billions to trillions of times greater than those generated in hospital MRI machines, for example. These fields cause magnetars to erupt sporadically with bursts of high-energy radiation.