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Planets discovered in star cluster – one orbiting a Sun ‘double’
Astronomers have discovered a planet that is circling a star almost identical to the Sun in all respects in one of the oldest known open star clusters. The planet is one of three that have been found orbiting stars in Messier 67, a cluster around 2500 light-years away in the constellation of Cancer (The Crab). Planets orbiting stars outside the Solar system are now known to be quite common but only a handful, have been found in star clusters. The results are published in Astronomy and Astrophysics.
More than one thousand planets are confirmed orbiting stars outside the Solar System that are of widely varied ages and chemical compositions and are scattered across the sky. Very few have been found inside star clusters, something that is particularly odd as it is known that most stars are born in such clusters.
“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 (ESO, Garching, Germany), co-author of the new paper.
This is the first planet to be found not only in a star cluster but also orbiting a solar twin.
Professor Don Pollacco from the University of Warwick said: "Most stars like the sun form in groups so it’s important to know if their accompanying planets can withstand having massive stars as companions. To know that these companions do not impede planetary evolution, at least in this case, is reassuring!”
Professor Andrew Cameron from the University of St Andrews added: "It is very interesting to find that, even in a cluster environment as dense as M67 must have been when it formed, planetary systems survive in about the same numbers as we see among stars travelling solo through the Sun's neighbourhood."
Astronomers used the European Southern Observatory (ESO)’s HARPS planet hunter in Chile along with other telescopes in the world to carry out the research. They carefully monitored 88 selected stars in Messier 67 over a six year period looking for tiny tell-tale motions of the stars towards and away from Earth that reveal the presence of orbiting planets. Many of the cluster stars are fainter than those normally targeted for exoplanet searches and trying to detect the weak signal from possible planets pushed HARPS to the limit. These results were supplemented with observations from several other observatories around the world. The UK community expects to build upon these exciting results using a range of facilities supported by STFC. STFC subscribes to ESO giving UK astronomers access to ESO telescopes.
STFC’s ‘Seeing the Universe in all its light’ roadshow demonstrates why it is important to study objects at different wavelengths using different telescopes. It showcases some of the best telescopes in the world.
