Astronomers using ESO telescopes and others around the world have found three new planets orbiting stars in a cluster called Messier 67.
Only a handful of such planets in clusters were known up to now.
And, surprisingly, one of the newly found planetary host stars seems to be an almost perfect solar twin
— a star that is essentially identical to our own Sun.
It’s the first exoplanet orbiting a solar twin in a star cluster to be discovered.
This is the ESOcast! Cutting-edge science and life behind the scenes of ESO, the European Southern Observatory.
Exploring the ultimate frontier with our host Dr J, a.k.a. Dr Joe Liske.
Good news everyone! 3 brand new exoplanets have been discovered.
Considering that we already know about a thousand exoplanets, that might not sound like much
but this finding is in fact, a little unusual because these 3 planets orbit stars inside a cluster of stars known as Messier 67.
These recent discoveries confirm that planets in clusters are quite common — although very hard to spot.
They will also allow scientists to examine how planets form in the crowded environment of a star cluster.
To find the new exoplanets, astronomers used the HARPS instrument on the 3.6-metre telescope at ESO’s La Silla Observatory.
They carefully monitored 88 selected stars in Messier 67 for a number of years.
That allowed them to look for the tiny tell-tale motions of the stars that reveal the presence of orbiting planets.
Three planets were discovered in the cluster.
Two of these planets orbit stars similar to the Sun,
and one orbits a more massive and evolved red giant star.
The first two planets both have about one third the mass of Jupiter and orbit their host stars in seven and five days respectively.
The third planet takes 122 days to orbit its host and is more massive than Jupiter.
The host star of one of the planets turned out to be a remarkable object
— it’s one of the best solar twins ever identified.
The star is almost identical to the Sun in terms of its mass, age, chemical composition and other characteristics.
Also, it’s the first solar twin in a cluster that has been found to host a planet.
Solar twins, solar analogues and solar-type stars are categories of stars based on how similar they are to our own Sun.
Solar twins — stars almost identical to the Sun — are very rare,
but the other classes, where the similarity is a lot less precise, are much more common.
Astronomers had not found many planets around cluster stars in the past, but now they are finally showing up.
The new results from the HARPS instrument show that planets in open star clusters
are probably about as common as they are around isolated stars
...so that’s a lot of planets!
This is Dr. J signing off for the ESOcast.
Join me again next time for another cosmic adventure.
Transcription by ESO; translation by -