January 15, 2014
ESO Researchers Discover Three New Planets In Messier 67
[ Watch the Video: Messier 67 A Perfect Lab For Studying Planet Formation ]
Gerard LeBlond for www.redorbit.com - Your Universe Online
There are two main types of star clusters: open clusters and globular clusters. The open cluster is a group of stars recently formed in a single cloud comprised of gas and dust. The globular clusters are larger and older with the stars orbiting around the center of the galaxy. Only six planets have been discovered in open clusters and none have been found in globular clusters.
Messier 67 is a star cluster located about 2,500 light-years from the constellation of Cancer. It contains around 500 stars and HARPS was pushed to its limits in the search for possible planets.
Study lead author Anna Brucalassi, from Max Planck Institute for Extraterrestrial Physics in Garching, Germany, said, “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.”
The HARPS instrument was attached to ESO’s 3.6-meter telescope located at La Silla Observatory in Chile. Along with several other observatories, the team monitored 88 stars in Messier 67 for a six-year period looking for any sign of orbiting planets within the cluster.
[ Watch the Video: Three Planets Found In Star Cluster ]
Two planets were found orbiting stars similar to our sun and are about one third the size of Jupiter. They orbit their star in seven and five days respectively. The third planet is larger than Jupiter and orbits a massive red giant star in 122 days.
The planet that has the seven-day orbit is unique because it is circling a star that is considered to be a twin to our own sun. It is the first solar twin discovered to have an orbiting planet.
Two of the planets are called “hot Jupiters” because they are about the same size as our Solar System's largest planet but closer to their host star. All three stars are closer than the habitable zone where water could exist.
“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 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.” adds study coauthor Luca Pasquini, of the ESO.