Mary Edith Lowery, age 13, of Sandston, Virginia, for her question:
What exactly are pulsars?
We ordinary space- agers do not know the notion of radio contact with other worlds. Neither do the expert astrophysicists. However, early this year, the introduction of the first pulsar somewhat stunned us all. Its strange radio pulses just might be intelligent signals from beings on some remote alien world, or so it seemed.
The first pulsar was discovered almost by accident. Astrophysicists in Cambridge, England, built a special radio telescope to capture fast bursts of radio energy from celestial sources. The rectangular dish is a grid of 16 rows, each made of 128 special copper rods. It measures 470 meters from east to west and 40 meters from north to south. Its original purpose was to filter out interferences from the solar wind and from interplanetary plasma. Operations began in July 1967 and very soon the new radio telescope made an astonishing discovery. It traced a repeating short short pattern of radio bursts from a fixed spot in the heavens. This was a brand new type of celestial phenomenon.
The first excitement was followed up with more tests and checks. No doubt about it. The regular radio signals were coming at 1 1/3 second intervals day after day, month after month. The source of the pulsing energy was estimated to be around 100 parsecs closer to us than Polaris. In January of 1968, this newly discovered type of celestial object was introduced to the world as a pulsar.
And the everyday world was agog. Those short pulses of radio energy are far more interesting than repeated up and down peaks on a graph. Each brief pattern jerks and jogs with amazing variations of frequencies and intensities. The details are checked and charted in milliseconds, or units of 1,000 parts of a second. The impossibly short pulses plus their infinite variation caused even the experts to wonder whether the pulsar was sending intelligent radio signals across the universe.
Such excitement sent worldwide astronomers in search of more evidence. Two more pulsars pulsing at similar intervals were located in our part of the Galaxy. Another with a pulse rate of one quarter second was located. The excitement has not died down far from it. But astrophysicists now take the view that the pulsars are natural cosmic events, unrelated to signals from intelligent beings. They are busy gathering evidence to discover what kind of celestial object can possibly emit such short, rhythmical radio pulses. At present, a half dozen or so likely theories have been suggested. But nobody knows for certain.
Most experts suspect that the strange radio emissions comes from either very ancient white dwarf stars or from nucleon stars that could be due for supernova explosions. Every effort is being made to mcasure and pinpoint these invisible cosmic radio stations. The dimensions of CP 1919, the first pulsar to be introduced to our stargazing world, are estimated to be at least as small as the planet Mercury. However, the busy little body may contain almost as much matter as our massive sun.