British scientists report detecting distant planet

July 25, 1991|By New York Times News Service

Astronomers say they have discovered a planet around a distant star -- a claim that, if confirmed, would mark the first established detection of a planet beyond the solar system.

What they have observed appears to be stranger even than its discoverers imagined: A massive object orbiting the remnant of a star that collapsed in a violent explosion.

British astronomers, in today's issue of the journal Nature, reported that they had observed fluctuations in radio signals from such a star, a neutron star also known as a pulsar. They believe that these fluctuations are caused by the gravitational effects of an orbiting companion with about 10 to 12 times the mass of Earth.

The rate of radio pulses, usually three per second, would speed up and then slow down in a cycle that repeated itself every six months.

The finding is not likely to be accepted without considerable caution and further study. Despite many clues from visual, infrared and radio telescopes in the last decade, astronomers have yet to find conclusive evidence of other planetary systems, though their existence is generally assumed.

The discovery of a planet in orbit around a pulsar could upset theories about the formation of planetary systems, the birth of pulsars and other dynamics and repercussions of exploding stars, known as supernovas. Neutron stars are extremely dense objects remaining after the explosive collapse of a dying star. Those that rotate rapidly, flashing bursts of radio energy at regularly spaced intervals, are known as pulsars.

In their report, Dr. Andrew G. Lyne and colleagues at the Nuffield Radio Astronomy Laboratories at the University of Manchester in England said their observations of regular perturbations in radio signals over the last five years "imply the existence of a planet-size companion" orbiting pulsar 1829-10, about 30,000 light-years from the solar system.

Although there is some chance that the observed fluctuations are caused by an unexplained rotational instability in the pulsar, the scientists said the presence of a planet is the most likely explanation.

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