Astronomers find planet with Jupiter-like orbit

Sunday, June 16, 2002

WASHINGTON -- Astron-omers say they have discovered a planet circling a distant star in an orbit that resembles the orbit of Jupiter.

Geoffrey Marcy of the University of California, Berkeley, and Paul Butler of the Carnegie Institution of Washington said the planet, about five times the size of Jupiter, is traveling around a sun-like star at an orbital distance like the orbital path that Jupiter follows around our sun.

The newly discovered planet is one of three planets circling a star, called 55 Cancri, that is about 41 light-years away from Earth. A light-year is about 5.8 trillion miles.

"This is the first time that we've found a family of planets that has some similarities to our own solar system," Marcy said.

The new planet circles 55 Cancri at a distance of 5.5 astronomical units, close to the 5.2 AU orbit of Jupiter. An AU is the distance between the Earth and the sun, about 93 million miles.

The two other planets around 55 Cancri are also Jupiter- or Saturn-sized bodies, but they orbit much closer to the parent star. One is in an orbit of about 9 million miles and the other is about 23 million miles.

Marcy and Butler also announced they had found 13 other planets orbiting distant stars, bringing to 91 the total number of known extrasolar planets.

The team uses a technique that measures the very slight wobble of a central star and then uses the magnitude of this motion to determine the presence of orbiting planets, the size and shape of their orbits and their mass. The technique works only for larger planets.

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