Three Exoplanets Spotted Around Solar Twin in Star Cluster Messier 67

A team of international astronomers using ESO's HARPS and other telescopes, has discovered three new exoplanets orbiting around a solar twin in a star cluster Messier 67, reveals a European Southern Observatory finding.

Over one thousand planets have been spotted outside the Solar System but very few have been noticed in star clusters. The three planets orbiting stars in the cluster Messier 67, the oldest and best studied cluster close to the Earth, were discovered using the ESO's HARPS at the La Suilla Observatory, Chile, along with other powerful telescopes around the world. 

"In the Messier 67 star cluster the stars are all about the same age and composition as the Sun. This makes it a perfect laboratory to study how many planets form in such a crowded environment, and whether they form mostly around more massive or less massive stars," Anna Brucalassi (Max Planck Institute for Extraterrestrial Physics, Garching, Germany), lead author of the new study, said in a statement.

For over six years the astronomers carefully observed 88 selected star candidates in Messier 67, which lies 2500 light years away in the constellation of Cancer, and has nearly 500 stars. They monitored the intricate wobbles of the stars towards and away from Earth that indicate the presence of orbiting planets.

After a constant watch, the astronomers finally detected three exoplanets in which two were seen orbiting stars similar to the Sun and one was seen orbiting a more gigantic red massive star. The  first two planets have a mass one third of Jupiter and they were seen orbiting around their host star in seven and five days. On the other hand, the third gigantic planet (more massive than planet Jupiter) was observed taking nearly 122 days to orbit around its host star.

This is the first solar twin to be discovered in a cluster that has a planet. Also the two exoplanets are 'hot Jupiters', they are similar to Jupiter in size but closer to their parent star, due to which they are hotter. The three planets are closer to their host stars making it difficult for water to exist there.

"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," says Luca Pasquini (ESO, Garching, Germany), co-author of the new paper. "The new results are in contrast to earlier work that failed to find cluster planets, but agrees with some other more recent observations. We are continuing to observe this cluster to find how stars with and without planets differ in mass and chemical makeup."

The findings were reported in Astronomy & Astrophysics. 

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