Globular clusters are spherical-shaped or globular stellar groupings — hence the name — which can contain millions of stars. There are about 200 of them in the Milky Way, but few are as intriguing to astronomers as the E 3 cluster.
It is situated around 30,000 light-years away in the southern constellation Chameleon. A team of Spanish and Italian astronomers has named it “a ghost from the Milky Way’s past” in an article published recently.
“This globular cluster and a few similar ones, such as Palomar 5 or Palomar 14, are ‘ghosts’ because they appear to be in the last stages of their existence, and we say ‘from the past’ because they are very old. They were formed when our galaxy was virtually new-born, 13,000 million years ago,” said Carlos de la Fuente Marcos, an independent astronomer who collaborates with colleagues from the Northern Catholic University and ESO in Chile, and the University of Padua in Italy.
E 3 is hidden behind younger and brighter objects located between the cluster and Earth, but it has been possible to analyze it thanks to the Very Large Telescope (VLT) in the European Southern Observatory (ESO) in Cerro Paranal, Chile. The data obtained revealed some surprises.
“Unlike typical globular clusters, which contain hundreds of thousands and in some cases millions of stars, the object studied only has a few tens of thousands of them,” said De la Fuente Marcos. “Additionally, it doesn’t have the typical circular symmetry, but a much distorted, almost ghostly rhomboidal shape contorted by the galactic gravitational waves.”
According to another study on E 3 by Michigan State University (USA) researchers, this cluster is chemically homogeneous — it doesn’t have several star populations in its interior.
“This is characteristic of an object that was created in block in one single episode, like what is supposed to have happened when our galaxy was born — very large star clusters containing millions of stars were formed — but what remains of them today are objects like E 3, ghosts from a distant past,” said De la Fuente Marcos. He explained that the study of these objects “enables us to gain insight into the infancy of the Milky Way.”