Astronomy: Puzzling Pulsars

The more that astronomers learn about pulsars, the still-to-be-identified bodies that are sending strange beeping signals from the Milky Way, the more difficult to identify the pulsars become. Last week, at a Manhattan gathering of the growing group of pulsar specialists, scientists from the Kitt Peak National Observatory in Arizona and the Lick Observatory in California disclosed that Pulsar I not only sends out high-frequency radio signals every 1.3 seconds, but also gives off light flashes just about half as often. The conferees were beginning to ponder this new information when a tardy University of California astronomer, David Cudaback, still bleary-eyed from long nights at the Lick Observatory, arrived with word that the light flashes are inexplicably irregular: they speed up or slow down by as much as 10%.

What does it all mean? The confusing combination of light and radio pulses has persuaded most astronomers that pulsars are not white dwarfs (small, dying stars). And although British pulsar discoverers initially nicknamed them LGM (little green men), most astronomers have now given up the idea that the four known pulsars might somehow be powerful electronic beacons from a super civilization in distant space. Still in the running is the notion that they may be neutron stars: tiny bodies of densely packed neutrons, which are atomic particles having no electrical charge. The only thing that seems reasonably certain is that the pulsars are not much larger than Earth and are 50 to 400 light-years away. Says Astrophysicist A.G.W. Cameron of Yeshiva University, the conference chairman: "It's going to be a damn hard job to make any theory fill the bill."