Exoplanet toll hits 100 as another Jupiter found

Artist's concept of an exoplanet

(CNN) -- Astronomers said this week they had identified at least eight more planets outside our solar system, bringing the number of known or suspected exoplanets to about 100.

The group, unveiled during an unprecedented string of planet discoveries, includes one much like Jupiter, the second such rare find announced within days.

European scientists, who reported the new objects at an exoplanet conference in Washington, D.C., said the planet closely resembles Jupiter in some crucial ways.

"It is about the mass of Jupiter," said Didier Queloz, a member of the European planet hunting team at the Geneva Observatory in Switzerland.

"The key element, however, is that is has a circular orbit, not an elliptical one. This reminds us strongly of our own solar system," he said.

In contrast, the other Jupiter-like planet, announced along with 14 other new planets by a U.S.-led team Thursday, is four times as massive as Jupiter and has a slightly elliptical orbit.

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But in some ways the latter seems more like Jupiter. It goes around its star a comparable distance and speed as Jupiter, which orbits the sun at 5.2 astronomical units, slightly more than five times the distance between the sun and Earth.

The former orbits at 3.7 AUs from Gliese 777A, a sun-like star about 52 light years away.

Why the big fuss over which planet is most like Jupiter? Similarities could indicate which planetary systems offer the most promise in the search for terrestrial-like planets.

Most identified exoplanets have lopsided orbits extremely close to their parent stars, in contrast to the circular, more distant orbit of Jupiter, the largest planet in our solar system.

With its large mass and stable orbit, Jupiter could have fostered a life-friendly environment in our space neighborhood, according to astronomers.

The gas giant is thought to have protected terrestrial life in its infancy, ingesting swarms of primordial comets before they collided with Earth.

Most exoplanets found so far are more massive than Jupiter. Although one announced last week has less than half the mass of Saturn, the second largest planet in our solar system.

With improvements in technology and search techniques, scientists using space- and ground-based telescopes expect to detect Earth-sized planets within a decade or so.