PSR J2222−0137

PSR J2222−0137 is a nearby intermediate-mass binary pulsar at a distance of $267$ pc (approximately 870 light-years), whose low-mass neutron star's companion is a white dwarf (PSR J2222−0137 B). The white dwarf has a relatively large mass of and a temperature less than 3,000 K, meaning it is likely crystallized, leading to this Earth-sized white dwarf being described as a "diamond-star".