About J1737-0314D
J1737-0314D is a rare pulsar. It spins once every 2.89 ms and has a dispersion measure of 78.8 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.