A team of international astronomers have found that giant planets are more common around the stars inside Messier 67 than outside the cluster.
Astronomers have found an exceedingly large number of hot Jupiter planets inside a nearby star cluster called Messier 67. The results are quite surprising since only few exoplanets have been found within star clusters to date.
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Messier 67 is one of the oldest known open star clusters. It is roughly 2500 light years away from the Earth and contains more than 500 stars. Scientists have been studying a carefully chosen sample of 88 stars in the cluster for a long period of time mainly to get insight into stellar evolution.
Using HARPS and other powerful instruments, scientists have looked at the signatures of giant planets or hot Jupiters orbiting close to the star in the cluster and have found telltale evidence of the presence of such planets around three stars, indicating that giant planets far more commonly form and persist in a densely packed cluster environment than thought. The stars in the cluster are roughly the same age as the Sun and have similar geological properties.
“We want to use an open star cluster as laboratory to explore the properties of exoplanets and theories of planet formation” explains principle investigator Roberto Saglia. “Here we have not only many stars possibly hosting planets, but also a dense environment, in which they must have formed.
Hot Jupiters are giant exoplanets that are comparable in size to Jupiter, the largest planet of our solar system. But much hotter since they are orbiting very close to their host stars, having an orbital period of less than 10 days.
“The new results mean that there are hot Jupiters around some 5% of the Messier 67 stars studied — far more than in comparable studies of stars not in clusters, where the rate is more like 1%.” Co researcher Anna Brucalassi said.
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Researchers have ruled out the possibility that these exotic giants were actually born within the cluster since the conditions are not suitable for formation of such planets. They were likely born somewhere outside and then moved closer to their host star. Their inward migration could be a result of close encounter with neighboring stars or even with planets in neighboring solar systems.