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Our sun's distant twin has an orbiting planet

By Deborah Netburn

1:12 PM PST, January 15, 2014

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In an open cluster of stars about 2,500 light-years from Earth, scientists have discovered three new exoplanets, including one that orbits a star almost identical to our sun.

Although scientists have confirmed 1,000 exoplanets in the last several years, this is the first time they have ever seen one orbiting what's known as a "solar twin" in a cluster of stars.

Detecting planets in star clusters has not been easy, and most of the exoplanets discovered so far have been found orbiting lonely stars that live in relative isolation.

To find these three new planets, researchers at the Max Planck Institute for Extraterrestrial Physics in Germany spent six years monitoring 88 stars in a cluster called Messier 67. The cluster lies in the constellation Cancer, and consists of about 500 stars. (Click through the gallery above for a star map and a view of the full cluster).

Using the European Southern Observatory's HARPS telescope in Chile, as well as a few other telescopes around the world, the scientists looked for barely perceptible movements in the stars that would indicate they were being gently pulled or pushed by the presence of a nearby exoplanet.

Using this technique, they found three exoplanets orbiting three different stars in the cluster. A planet larger than Jupiter was found orbiting a red giant star that is both older and larger than our sun. The two other planets, which were about a third the mass of Jupiter, were found orbiting stars more similar to our sun, including one which is almost identical in age, mass and chemical makeup to our life-giving star.

If you are hoping the planet might be an Earth twin, you are out of luck. It is much larger than Earth, and it also lies so close to its sun that its year lasts just a week. It is way too close to its star to support water. 

But the astronomers are still excited about the discovery.

"These new results show that planets in open star clusters are about as common as they are around isolated stars -- but they are not easy to detect," the ESO's Luca Pasquini, a coauthor of a paper describing the team's findings that was published in the journal Astronomy and Astrophysics, said in a statement. "We are continuing to observe this cluster to how stars with and without planets differ in mass and chemical makeup."  

Below, you can take a video tour of the star cluster, thanks to the ESO.

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Earth-twin, where are you?? Follow me on Twitter and we'll keep an eye out together.

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