Asked by James Bannister
A magnetar is a type of neutron star, a strange object with an incredibly powerful magnetic field that powers the emission of highly energetic X-rays and gamma rays. Neutron stars are formed when the largest stars in the universe reach the end of their lives. When these stars run out of fuel, their core collapses causing outer layers to come crashing in towards the centre.
As stars are so large the crushing forces created can be phenomenal. These pressures can squash the core of the star together and because of this, a neutron star – and hence a magnetar – is made of some of the densest material in the known universe. In fact, their material is so dense that one teaspoon of it contains the same amount of mass as 900 Egyptian pyramids.
Image Credit: ESO