Astronomers this week have announced the discovery of three planets found within the Messier 67 star cluster. The finding is significant because planets have rarely found orbiting stars that are part of star clusters. The new research shows that planets may actually be just as common within star clusters as they are throughout the rest of the galaxy.
“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,” said Luca Pasquini, co-author of a paper on the findings published in the journal Astronomy & Astrophysics and an astronomer with the European Southern Observatory. “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 Messier 67 star cluster is located around 2,500 light-years from our solar system and is made up of around 500 stars. Astronomers observed around 80 stars in the cluster for over six years while searching for exoplanets.
Two of the newly-found planets are Jupiter-sized, though they orbit much closer to their stars than Jupiter does. The third planet was found orbiting a star named HIP 102152, which has previously been identified as being nearly identical to our sun. All three of the planets orbit more closely than the habitable zones of their stars, meaning that liquid water cannot exist on their surfaces.
“In the Messier 67 star cluster the stars are all about the same age and composition as the Sun," said Anna Brucalassi, lead author of the paper and a researcher at the Max Planck Institute for Extraterrestrial Physics. "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.”
Image via ESO/L. Calçada