The Pulse of Another World

By MICHAEL D. LEMONICK

If countless stars fill the firmament, they must be circled by countless planets -- or so everyone assumes. In the fertile minds of fiction writers, the distant worlds have taken on every imaginable name, from Krypton to Ork, and spawned every imaginable creature, from the Klingons to the Ewoks. But in real life no earthbound astronomer has ever proved the existence of a single planet outside our solar system.

Now a team of three astronomers in Britain claims to have spotted solid evidence of a faraway world. Writing in the British journal Nature, Andrew Lyne and colleagues at the University of Manchester's Jodrell Bank radio observatory report an object between 10 and 15 times the mass of the earth, orbiting a special kind of star called a pulsar that lies some 25,000 light- years (140 quadrillion miles) away.

Pulsars are fast-spinning, ultra-dense clumps of neutrons -- generally the husks of stars that have exploded. They get their name from the powerful radio pulses that they emit at precisely regular intervals. It was an anomaly in these pulses that led the Manchester astronomers to focus on one particular pulsar -- and convinced them that a planet whirled around it. The pulsar spins on its axis three times a second, raking the earth with a beam of radio waves each time. But, says Lyne, periodically "the pulses would arrive about one- hundredth of a second earlier than they should, and then, three months later, they would be one-hundredth of a second later."

Their conclusion: the pulsar is wobbling, pulled by the gravitational field of a planet that orbits the star once every six months. When the planet is nearest earth, it tugs the pulsar in our direction, and the distance that the radio pulse travels to reach us starts to get shorter. Three months later, the planet pulls the pulsar the other way, and the distance the pulse must travel begins to lengthen.

The theory appears to be sound, but, notes David Black, director of Houston's Lunar and Planetary Institute, the history of astronomy is "littered with the bones of claimed detections." Lyne admits that other phenomena might be causing the observed deviations in the radio waves, but "the most likely interpretation," he maintains, "is that there is a planet there." Many other experts think Lyne is right. "Now that we see it," said Ramesh Narayan, a Harvard astronomer, "it is up to us to explain how it could happen."

Lyne's work provides no answer to the most tantalizing question in astronomy: Is there life on other planets? In this case, life would be difficult on a planet whose sun is a relatively tiny, dim pulsar. Astronomer Black figures that in about 10 years, telescopic instruments may be sophisticated enough to focus on the planet itself, rather than just the pulsar. Even if no Klingons are immediately found, the knowledge gained from examining the distant planet will make it easier to explore the countless other worlds waiting to be discovered.

With reporting by Andrew Purvis/New York