Astronomers are puzzled over an enigmatic companion to a pulsar

The mysterious entity has a mass somewhere between that of a neutron star and a black hole

illustration of a mysterious object orbiting a pulsar

An unseen object orbiting a pulsar might be an exceptionally lightweight black hole (illustrated), a very heavy neutron star, or something else entirely.

Daniëlle Futselaar/

Circling around a pulsar in our galaxy is a mysterious entity that is either a very heavy neutron star, one of the lightest black holes ever discovered, or an exotic and never-before-seen quasi-stellar object.