About J1623-6936
J1623-6936 is an epic pulsar. It spins once every 2.41 ms and has a dispersion measure of 46.4 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.