About J1641+3627D
J1641+3627D is an epic pulsar. It spins once every 3.118 ms and has a dispersion measure of 30.45 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.