Two planet-tracking scientists at Stony Brook University have helped pinpoint a jumbo "exoplanet" dubbed a young Jupiter orbiting a sunlike star in a constellation about 100 light years away.

A light year is equivalent to about 6 trillion miles and the term exoplanet defines any planetary body outside our solar system that is orbiting a star.

The new exoplanet is a key discovery, scientists said yesterday, because it is uncannily similar to the gas giant Jupiter, the big daddy planet in our solar system characterized by a whirling Great Red Spot and a multitude of moons.

"This is a big deal," said Rahul Patel, a doctoral student in Stony Brook's department of physics and astronomy and a member of the international team that found the new planet.

"It's a step toward finding something that looks like our solar system and that's crazy amazing because it's really important in understanding how our solar system may have formed."

The new planet, which has been named 51 Eridani b is the first to be detected by the supersensitive Gemini Planet Imager, which allows scientists to seek new worlds in regions of the cosmos where they were unable to obtain clear images in the past.

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Stanimir Metchev, a physics and astronomy professor at Western University in Canada and an adjunct professor at Stony Brook, was a co-investigator in the discovery project, reported in Friday's edition of the journal Science.

"It also harbors dust and ice," Metchev said, noting the debris is comparable to dust and ice grains produced by collisions among asteroids and comets in our solar system.

Last month, NASA scientists found a "close cousin to Earth" that may harbor life 1,400 light years away in the constellation Cygnus. The team that discovered the Jupiter look-alike says both finds are significant.

Investigators at the SETI Institute, a space science nonprofit in California that also participated in the search for 51 Eridani b, describe the Gemini imager as an extraordinarily complex device that measures about the size of a small car.

It was attached to one of Earth's most massive telescopes, the 8-meter Gemini South instrument in Chile. With the Gemini onboard, the telescope began its sweeping scan of the outer reaches of the local heavens last year, SETI scientists said.

Imaging has revealed a large planetary body still in early formation revolving around the bright star. "It's only about one-and-a-half times more massive than our sun and the exoplanet is about two times more massive than Jupiter. So it's not far out crazy heavy," Patel said.

"Other exoplanets have been eight times larger than Jupiter," Patel, said referring to the growing zoo of gargantuan orbs that scientists increasingly say populate the universe.

Patel said the newly discovered gaseous body is situated in the constellation Eridanus -- the so-called river -- in the Milky Way, the same galaxy as our solar system, making it a galactic neighbor.

Other scientists see the new exoplanet as planetary kin.

"It is a cousin of Jupiter," said Franck Marchis, planetary astronomer at the SETI Institute, which has aims of both exploring deep space and searching for extraterrestrial life on distant spheres.

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Marchis said scientists can detect the exoplanet's temperature and have made note of its brightness.

"It's hot because it's a young planet," Marchis said. "The star is only 20 million years old. That's a baby star still in its formation. And the fact that there is already a large planet is very interesting because we really don't know when our Jupiter was formed," as our own solar system took shape, Marchis said.

But scientists can look at young planets, Marchis said, and begin to grasp how planetary systems evolve.