What Are Pulsars?

In 1967, scientists detected pulsing signals coming from far-off outer space. These bursts of energy reached earth with such a regular pulse rate that it seemed they were being sent by beings on another world. At first they were called LGMs, for “Little Green Men.”

Later, it was discovered that these signals came from stars called pulsars. When a star burns up its fuel and becomes very small, it may begin to spin rapidly. As it spins, its gravity and magnetic forces also spin the clouds of gas and dust that surround the star.

But the gas and dust must spin much faster than the star itself. It’s like a spinning wheel with the star at the center. Because every part of a wheel completes one revolution in the same amount of time, the outer part of the wheel has to travel much faster than the inner part.

The same is true for a pulsar. The star is spinning rapidly in the middle of the swirling gas, and the particles at the outer edge of the gas clouds must travel very quickly to keep up with the spinning star. Eventually some of the gas particles can’t travel fast enough to keep up with the star; they break off and emit a pulse of energy. The spinning star sends one pulse our way for each revolution.

Most pulsars are spinning so fast that they revolve completely in less than a second. And the fastest pulsar known to us spins more than 200 times each second!