Jupiter-like planet found by McDonald Observatory team

EL PASO, Texas - A Jupiter-sized planet orbiting a young star in Earth's ''backyard'' could help reveal whether Earth, with its variety of life forms, is a unique jewel in the universe.

William Cochran, with the University of Texas' McDonald Observatory, said in a news release that finding a planet orbiting Epsilon Eridani, ''a star very similar to our own sun ... is like finding a planet in our own backyard - relatively speaking.''

Cochran is scheduled to present the findings Monday at the 24th General Assembly of the International Astronomical Union in Manchester, England.

''It's a very exciting discovery because ... the star itself is the closest star for which a planet has ever been discovered,'' Geoff Marcy, a University of California-Berkeley professor and co-author on the project, said Friday. ''It's only 10 light years away.''

''In the next 100 or 200 years, it will be one of the first stars humans visit,'' he said. A light year is the distance light will travel in a year in a vacuum, about 6 trillion miles.

Scientists discovered the planet by observing Epsilon Eridani as it wobbled on its axis. That wobble is caused by the planet's gravitational influence as it orbits the star. By measuring the size and frequency of the wobble, researchers can calculate the size of the guest planet and its distance from the host star.

Scientists hope the nearness to Earth of the host star will allow them to collect high-quality data. Pictures of the new planet may be possible in a few years as scientists fine-tune new instruments, including one that will help telescopes see clearly through the Earth's turbulent atmosphere.

Those observations could reveal whether the planet is a gas giant, like Jupiter, what it's made of, what chemicals are in its atmosphere, its temperature, whether it has moons or rings, and other vital statistics.

The new planet has about the same mass as Jupiter, said Artie Hatzes, a McDonald Observatory team member. The planet takes longer to orbit its star than any of the other planets identified outside our solar system. Jupiter takes about 11 years to orbit the sun, while the new planet takes about seven years to orbit its star.

Hatzes said the similarities of the Epsilon Eridani system to our solar system mean it could harbor a terrestrial planet like Earth that could sustain life.

Marcy said a ring of dust surrounds Epsilon Eridani. The dust can collide and stick together to form planets while the ice can provide water to sustain life.

''It probably would have a chance of having life-bearing worlds,'' Hatzes said, adding that an Earth-like planet probably would be inside the orbit of the newly discovered planet where it would receive more warmth from the star.

But Marcy points to what appears to be a unique feature of our solar system. Most of the planets move in nearly circular orbits. The new planet has an oblong orbit as do most of the other newly discovered planets.

Earth's circular orbit provides a relatively stable environment, evening out the extremes of cooling and heating that would be experienced on the surface of a planet with an oblong orbit.

What has been observed so far ''suggests the architecture of our solar system may be abnormal,'' Marcy said. ''We have a burning question as to whether our solar system is a rarity in the planetary zoo. It may be that life here is possible because of the circular orbit.''

Steve Maran, a NASA astronomer and a spokesman for the American Astronomical Society, said the discovery hints that there will be more to come.

''The fact that the McDonald team has found a planet so close to the Earth continues a trend of discovery of other solar systems that are all around us, which we didn't know until only a few years ago,'' Maran said. ''I think the more we keep looking, the more we find ... it's a really exciting development.''