Binary systems containing neutron stars are born when the cores of two orbiting stars collapse in supernova explosions. Neutron stars pack the mass of our sun into the size of a city. They are so dense and packed so tightly that the boundaries atoms nuclei disappear. In such systems, Einstein's theory of general relativity predicts that neutron stars emit gravitational radiation, ripples of space-time. This causes the orbits to shrink and gradually brings the neutron stars closer together. Shown here is such a system after about 1 billion years, when two equal-mass neutron whirl around each other at 60,000 times a minute. The stars merge in a few milliseconds, sending out a burst of gravitational waves and a brief, intense gamma-ray burst.
This animation shows the merger of two neutron stars from a horizontal perspective. Theory predicts that these kinds of collisions would not produce a long afterglow because there isn't much "fuel" — dust and gas — from the objects and in the region to sustain an afterglow