About J0058+6125
J0058+6125 is an uncommon pulsar. It spins once every 637 ms and has a dispersion measure of 128.3 pc cm⁻³.
The collapsed core of a star that exploded: about one and a half Suns of matter crushed into a ball the size of a city, held up only by the refusal of neutrons to be squeezed further.