About J1823-3543
J1823-3543 is an epic pulsar. It spins once every 2.425 ms and has a dispersion measure of 81.7 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.