The left panel shows X-ray emitting regions from three neutron stars, ‘PSR B0656-14’, ‘PSR B1055-52’ and ‘Geminga’, nicknamed the ‘three musketeers’, as measured by ESA’s XMM-Newton, down to scale. While the majority of the neutron stars surfaces emit at temperatures between 500 000 and 700 000 degrees Celsius, smaller spots have significantly higher temperatures, well above one million degrees Celsius. The dimensions of the hot spots are different for the three stars.
The right panel shows how the emitting surface of each star varies while the star rotates (note that the hotter and the cooler surface are not drawn to scale). From the animation, the hot spots for PSR 1055 and Geminga disappear for a fraction of the star rotation, while for PSR 0656 the hot spot is always in sight. This offers a new clue to understanding neutron star geometry.