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In less than a year, astronomers have advanced from not knowing if there are any planets around other ordinary stars beyond the solar system to finding striking evidence of planets orbiting at least five other stars. The latest discovery, announced Tuesday, seemed to bring the phenomenon of other planetary systems intriguingly close to home.

An astronomer from the University of Pittsburgh reported detecting the long-term gravitational effects of what appeared to be two large objects accompanying the star Lalande 21185, the fourth-nearest star to the sun.It is only 8.1 light-years away, while the other four stars that were recently found to have planets ranged from 35 to 50 light-years from the sun. A light-year, the distance light travels in a year, is nearly six trillion miles.

If the discovery is confirmed, experts said, Lalande's proximity will hold out the prospect of revealing studies of what an extrasolar planetary system is like.

Early indications, they said, were tantalizing because this system, unlike the others, appears to bear more of a resemblance to Earth's solar system, though the two observed planets - if that is what they are - are very likely to be inhospitable to life.

Finding yet another star with planets also encouraged some astronomers in their growing belief that planetary systems may be fairly common. But they cautioned that the search must be widened and intensified before that can be determined.

The discovery was described by George Gatewood of Pittsburgh's Allegheny Observatory at the American Astronomical Society meeting at the University of Wisconsin in Madison.

His research is based on 66 years of observations of Lalande, drawing on photographs of the star's motions during that time and eight years of more recent observations by new electronic light detectors. An analysis of the data indicated that the star's velocity had speeded up and slowed down as if a low-mass, slowly orbiting companion was pulling it along and then slowing it down because of gravitational effects.

"If these are not planets, what could be causing these accelerations?" Gatewood asked. "I can't think of any other explanation."

He said he had spent the last three months examining the results to rule out errors. He concluded that it was unlikely that the two types of observations and different analyses would have produced the same errors.

"I know there's something orbiting this star," Gatewood said, when asked how far he wished to go in interpreting the research. "I know it with a great deal of certainty. The details I don't know as well. Two planets are possible answers."

Other astronomers were cautious. "It's not very definitive," said Dr. Anita L. Cochran of the University of Texas at Austin. "But Gatewood's as good as anybody in this field. I would just like to see more data."

By studying the data, Gatewood determined that one of the objects appeared to be more massive than Jupiter and traveling a 30-year orbit of Lalande at a distance equivalent to Saturn's distance from the sun. The other object, probably less massive than Jupiter, has a 5.8-year orbit with a distance from the star comparable to the asteroid belt between Mars and Jupiter.

Lalande itself is a rather dim star, a red dwarf about one-third the mass of the sun that is visible through binoculars in the constellation Ursa Major.

David C. Black, director of the Lunar and Planetary Institute in Houston, said, "On the face of it, this looks more like what a planetary system should be, if that's what it is."

He had in mind the spacing of these putative planets, which appears to be more like the spacing in the solar system. In the previous discoveries, some of the planets were surprisingly close to their stars or extremely far away. And most of them were much larger than Jupiter.

"It's too soon to tell how common planetary systems are," Black said. "We need to survey at least 1,000 stars, which will be done in the next decade. Then we would get a statistical basis for estimating the occurrences of planetary systems."