In the late summer of 1967 radio astronomers detected some very unusual signals consisting of short pulses of radio noise arriving at approximately one second intervals. It was at first thought that perhaps a secret Solviet space satellite had been detected, but it was soon clear that the mysterious pulsating radio source came from among the very remote fixed stars. Detailed study proved the source to be extremely precise and regular, more regular than anything ever observed in nature. The next theory was that we had detected signals from an 'alien' spacecraft or distant planet. By the spring of 1,968, three additional pulsating radio sources had been discovered and today over 100 such sources are known. In all cases, the periods of pulsation are extremely regular (note the number of decimal places listed in the table), with periods ranging from 1/30 of a second for the fastest to just over three seconds for the slowest.

Today it is considered a fact that pulsars (as these objects came to be called) are the final remains of ancient supernovae explosions, rapidly rotating neutron stars. These neutron stars (see section on Birth of Stars) have intense magnetic fields and radiation streaming out of the north and south magnetic poles and can account for the properties of pulsars, if high-speed rotation is assumed. One of the fastest pulsars (the Crab Nebula) his been observed flashing pulses of visible light on and off 30 times each second. The fastest and therefore youngest of the pulsars have been found at the sites of supernova detonations and it is known that these objects have high velocities. Astronomers therefore assume that the longer period (older) pulsars may have moved far from their original sites at the heart of a superhova. Pulsars are galactic objects of powerful intensity and extreme regularity. The column in the listing, "Period," will give you an idea of the degree of regularity for these objects.

Copyright (c) 1997-99 Michael Erlewine