A European space telescope has discovered 10 previously unknown alien planets, including two Neptune-like objects that circle the same star, researchers announced Tuesday.

France's CoRoT satellite detected the 10 alien planets, all of which are gaseous like Saturn or Jupiter. However, they exhibit a range of masses, densities, orbital characteristics and other properties, researchers said. The new discoveries highlight the diversity of worlds beyond our solar system and boost the confirmed count of extrasolar planets up to 565, they added.

"Ever since the early days of exoplanet astronomy, we’ve been amazed by the variety of planets that have been discovered: gaseous giants larger than Jupiter and smaller, rocky bodies, down to masses comparable to the Earth’s," said Malcolm Fridlund, the European Space Agency's project scientist for CoRoT, in a statement. [Photos: The Strangest Alien Planets]

Researchers announced the findings Tuesday, at the Second CoRoT Symposium in Marseille, France.

Alien planet haul

Like NASA's Kepler Space Telescope, CoRoT searches for alien planets by what is known as the transit method. This technique looks for tiny dips in a star's brightness that could potentially be caused by a planet passing in front of it from our perspective.

The 10 newly discovered alien worlds have all been confirmed by follow-up observations using ground-based telescopes. Seven of the discoveries are so-called "hot Jupiters," gas giants that orbit extremely close to their parent stars. Another one is smaller than Saturn, and the other two are Neptune-like siblings circling the same star.

While all the newfound alien planets are gaseous, they make up a diverse group. Their densities, for example, span a wide range, from values similar to that of Saturn (the least dense planet in our solar system) to densities comparable to that of rocky Mars, researchers said.

One planet orbits a 10-billion-year-old star, which is twice as old as the sun. Another circles a star just 600 million years old. Two of the exoplanets also lie on highly elongated orbits — a surprise to scientists, considering how unstable such paths are thought to be.

A planetary zoo

Since the first planet beyond our solar system was discovered back in the 1990s, astronomers have discovered an astonishing diversity of alien worlds.

"The new set of 10 planets that we announce today are no exception, exhibiting as they do a rich list of very interesting properties," Fridlund said.

To date, astronomers have confirmed at least 565 alien planets, and the Kepler project has already identified 1,235 more "candidate" planets that await in-depth follow-up study. Researchers have predicted that at least 80 percent of Kepler's planetary candidates will eventually be confirmed.

Since its launch in 2006, CoRoT has detected several hundred candidate planet-hosting stars. The 10 new finds bring the satellite's total number of confirmed planet discoveries to 26.

Many more finds will likely follow — from Kepler, CoRoT and other instruments — helping astronomers better understand alien planets on a broader scale, researchers said.

"Although the study of exoplanets is relatively young, we have already reached a stage where we can characterize the details of worlds orbiting other stars, and CoRoT is making a crucial contribution to this field," Fridlund said. "With hundreds of systems observed to date, we no longer have to worry about 'taming the beasts' and we can dedicate our efforts to the 'zoology' of exoplanets, which is enormously enhancing our knowledge about planetary systems."

This article was reprinted with permission from SPACE.com.

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