PSR J0737-3039 system

A binary system of two massive, highly compact neutron stars only about 20 km across, orbiting each other every 2.4 hours at speeds of a million kilometres per hour around a common centre of gravity. Separated by a distance of just a million kilometers, both neutron stars emit lighthouse-like beams of radio waves.

Gravitational time dilation causes the pulse rate from one pulsar to slow when near to the other, and vice versa. The pulses from one pulsar when passing close to the other are delayed by the curvature of space-time.

The two co-rotating neutron stars lose energy due to the radiation of gravitational waves. This results in a gradual spiralling in of the two stars towards each other until they will eventually coalesce into one body in approximately 85 million years.

As in a balanced see-saw, the heavier pulsar is closer to the centre of mass, or pivot point, than the lighter one.

Overview

Primary: PSR J0737-3039 A
Secondary: PSR J0737-3039 B