Earth"s second cousin

SCIENCE fiction teleserials like Star Trek may not be gifts of over-stretched imagination, after all. Two independent sightings of a planet around a sun-like star dispel the notion that our solar system is unique. This has freshly fuelled inquiries into the possibility of extraterrestrial life-forms.

The star, 51 -Pegasus, is eight billion years old and 40 light-years away and is visible to the naked eye from earth's northern hemisphere. The new-found planet revolves around it in four days, less than five million miles from it, skimming the star's outer surface where temperatures reach roughly 1800oF.

Reports of the first siting, by Michel Mayor and Didier Queloz of the Geneva Observatory in Switzerland, on October 6, met with much skepticism. But after a four-day study scientists at the Lick Observatory near San Jose, California, confirmed this.

After hearing about the Swiss study, Geoffrey Marcy, professor of Physics and Astronomy at the San Francisco University, and Paul Butler, post-doctoral researcher at the University of California, Berkeley, made independent measurements of the 5 1 -Pegasus system.

Because it is revolving very close to the star, the planet is lost in the glare of the star's dazzling light and therefore not normally visible. During the obserations by the American scientists, which took four days, that is, the time in which the planet completes one revolution, the doppler's shift in the star's light was measured. The normal light spectrum experienced a wobble in the star's motion caused by the planet's gravitational pull. Says Marcy, "It pushes the star around like nothing we've seen".

As of now, the scientists do not know what the planet is comprised of - solids or gases, whether it is accompanied by other planets or is a solitary wanderer. They are also not sure about the origin of the planet. One possibility being investigated is that of the planet being thrown towards the mother star in a collision or a near-collision with another planet. The American scientists are carrying out further observations over a period of 10 days to find answers to some of these questions.

Until now, the only accepted planets were those belonging to a dead sun or pulsar, which is a dense, rapidly spinning remnant of an exploded star. Two or possibly three such planets were discovered three years ago by Alexander Wolszczan at the Pennsylvania State University.

With the weekly magazine Science News reporting the detection of a large planet around another star - the GL229 - about 30 light-years from the earth, scientists are waiting with great anticipation. Says astronomer Douglas Duncan, of the Adder Planetarium and the University of Chicago, "Planets are not easy to find... This is the decade in which we will find out just how com- mon planets are."

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