About J1129-53
J1129-53 is an uncommon pulsar. It spins once every 1,062.88 ms and has a dispersion measure of 77 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.