A neutron star merger is a type of stellar collision. When the two neutron stars meet, their merger leads to the formation of either a more massive neutron star, or a black hole (depending on whether the mass of the remnant exceeds the Tolman–Oppenheimer–Volkoff limit).

Most neutron stars are observed as pulsars. Pulsars are rotating neutron stars observed to have pulses of radiation at very regular intervals that typically range from milliseconds to seconds. Pulsars have very strong magnetic fields which funnel jets of particles out along the two magnetic poles.

Simply put, pulsars are rotating neutron stars. And pulsars appear to pulse because they rotate! Neutron stars for which we see such pulses are called “pulsars”, or sometimes “spin-powered pulsars,” indicating that the source of energy is the rotation of the neutron star.

When astronomers saw the cataclysmic explosion, they at first thought it was something called a short gamma-ray burst, or GRB. Most such flares develop when two neutron stars collide or there is some other destructive cosmic event.

Supernovae Leave Behind Neutron Stars or Black Holes In a nova, only the star’s surface explodes. In a supernova, the star’s core collapses and then explodes. In massive stars, a complex series of nuclear reactions leads to the production of iron in the core.

Most stars take millions of years to die. When a star like the Sun has burned all of its hydrogen fuel, it expands to become a red giant. After puffing off its outer layers, the star collapses to form a very dense white dwarf.

When a star burns through the last of its fuel, the object may collapse, or fall into itself. For smaller stars (those up to about three times the sun’s mass), the new core will become a neutron star or a white dwarf. But when a larger star collapses, it continues to compress and creates a stellar black hole.