What would happen if a black hole swallowed a neutron star?
Somewhere in the universe, a neutron star is swallowed by a black hole every ten minutes. This is the conclusion of a dying orbit, millions of years in the making, that has brought the two objects together. If the mass of the neutron star and black hole are similar, the neutron star is shredded as it spirals into the black hole, leaving behind a disc of gas that can create bright gamma, radio and other light rays. If the black hole is several times more massive than the neutron star, however, then the neutron star plunges into the black hole relatively undisturbed. What’s left behind in both cases is a black hole that’s heavier by about the mass of the Sun.
The orbit of the neutron star around the black hole decays because they are radiating gravitational waves – tiny ripples in the fabric of space-time. In the few milliseconds before the collision, a sizeable fraction of the mass of the Sun is converted into energy in the form of gravitational waves, and the system outputs more power (in the form of gravitational waves) than all the light from all of the stars in all of the galaxies in the entire universe combined.