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5th Planet Orbiting Nearby Star Found

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The Washington Post

Published: November 7, 2007

Updated: 11/07/2007 12:55 am

WASHINGTON - Astronomers have discovered a star orbited by at least five planets, marking the first time that a solar system with that many circling bodies has been found.

The central star, named 55 Cancri, has planets circling on paths similar to those in our solar system. Astronomers said that although the planets are unlike those in our solar system in terms of their size and distance from the sun, the fact that they are all in stable orbits is highly significant.

"Now we know our sun and its family is not unusual," said Geoff Marcy, an astronomer at University of California, Berkeley. "Our Milky Way has 200 billion stars and billions of solar systems. We suspect that many harbor Earth-like planets."

Although scores of extrasolar, or "exo-planets," have been located so far, they said, millions remain to be found.

One of the five planets has just been found. The new planet, which eluded detection for years because it was tucked in between two other orbiting planets that had been detected previously, appears to be a gas giant like Jupiter or Saturn and so is unlikely to sustain life.

However, it orbits in what is termed the "habitable zone" of its solar system - a band around the star where the temperature would permit liquid water to pool on solid surfaces - meaning that a rocky moon orbiting the planet, if there is one, could theoretically support life.

The star 55 Cancri is in the constellation Cancer, nearly 41 light years away. It has about the same mass as our sun and is easily visible with binoculars. The planets orbiting it, however, are too small to be seen with the most powerful telescopes and were located and identified by measuring the wobble their gravity creates in the motion of their sun.

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