There are billions upon billions of stars in the sky - but surprisingly few of them are a lot like our sun. Astronomers using the HARPS planet finder via the ESO’s 3.6-meter telescope at the La Silla Observatory in Chile have found three exoplanets in the star cluster Messier 67. One of these planets is incredibly unique, as it orbits the star eso1337, which is our true solar twin. This is the only known solar twin in a star cluster that has a planet. The research was led by Anna Brucalassi of the Max Planck Institute for Extraterrestrial Physics and will be published in an upcoming edition of the journal Astronomy & Astrophysics.
Messier 67 (M67) is an open cluster of stars in the constellation Cancer about 2,800 light years away. The stars are roughly the same age as our sun. It has been estimated that there are over 500 stars in the cluster, about 100 of which are very similar to our sun.
The planets were discovered during a six-year-long study of 88 stars in the cluster. The stars were chosen for their brightness and accessibility, as many of the stars are too faint to detect any orbiting planets. One of the stars with a planet that was discovered is a massive red giant, while the second is a main sequence star, like our sun. Eso1337, however, is nearly identical to our sun in relation to size, mass, and composition.
Unfortunately, none of these planets are in their respective star’s habitable zones, as they are far too proximal to the star to have liquid water. The planet orbiting the the red giant is more massive than Jupiter and takes 122 Earth days to complete a revolution. The other two planets have about 33% of Jupiter’s mass and have orbits that take about a week.
Astronomers will use these planets to learn how planets can form in these star clusters, where everything is relatively dense. It will also allow them to determine if planets are more or less likely to form around the more massive stars, or if less massive stars are more likely to be adorned with a planetary entourage.