The star is nearly identical to the Sun in all respects

Jan 15, 2014 13:49 GMT  ·  By
Artist's impression of an exoplanet orbiting a star in the cluster Messier 67
   Artist's impression of an exoplanet orbiting a star in the cluster Messier 67

Astronomers with the Max Planck Institute for Extraterrestrial Physics (MPI-EP), in Garching, Germany, announce the discovery of a new extrasolar planet in the star cluster Messier 67. The alien world orbits a rare solar twin, a star nearly identical to the Sun. 

Using telescopes such as NASA's Kepler, astronomers were until now able to discover more than 3,500 exoplanetary candidates, and confirm 1,000+ of them as actual planets. Despite these large numbers, very few exoplanets have thus far been found orbiting celestial orbs that are members of star clusters.

The object in Messier 67 is fortunately an exception. The MPI-EP team was able to discover a total of three new planets during its investigation, which relied on the use of the High Accuracy Radial velocity Planet Searcher (HARPS) high-precision spectrograph.

The instrument is installed on the European Southern Observatory's (ESO) 3.6-meter (11.8-foot) telescope at La Silla Observatory, in Chile. A number of other telescopes around the world were used to confirm the existence of these new alien worlds.

The fact that so few exoplanets were found inside star clusters continues to puzzle astronomers, since current theories indicate that the majority of stars are born inside such large-scale structures, and only then migrate outwards to form new stellar systems.

“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,” says MPI-EP astronomer Anna Brucalassi, the lead author of the new study.

Her team used HARPS and other telescopes to monitor a total of 88 stars in Messier 67, conducting regular observations over a period of 6 years. The cluster and the 500 stars it contains lies around 2,500 light-years away from Earth, in the constellation of Cancer (The Crab).

The group discovered two Sun-like stars and a red giant, which is a planet that has completed its main sequence, and is getting ready to transform into a helium-burning white dwarf. The first two planets are about a third the mass of Jupiter each, while the third is slightly larger than the gas giant.

“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,” explains ESO expert and study co-author, Luca Pasquini.

“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,” he concludes.