Open clusters are groups of stars that formed together from the same molecular cloud, and have remained gravitationally bound since then. Stars in an open cluster share the same chemical composition and astronomers use them as laboratories for testing several effects. The more stars in a cluster, the more useful it is for statistics and for finding stars in rare evolutionary stages.
For this reason, astronomers keep searching for massive clusters in our own Galaxy. At present, a dozen very young massive open clusters, less than 25 million years old, and a few very old ones, with ages of billions of years, descendants of similar objects in our Galaxy, have been found. However, there is a dearth of massive clusters with intermediate ages. Is this lack a consequence of some physical process in place or does it simply reflect our limitation to detect them?
The discovery of the Valparaíso 1 cluster at a relatively small distance from the Sun, suggests that many other similar clusters may lie hidden among lots of unrelated stars in the crowded regions of the inner Milky Way.
I. Negueruela, A-N. Chené, H. M. Tabernero, R. Dorda, J. Borissova, A. Marco, R. Kurtev, "A massive open cluster hiding in full sight", MNRAS, DOI: https://doi.org/10.1093/mnras/stab1117.
"Astronomers discover a massive star cluster, of intermediate age, in the constellation Scutum", Instituto de Astrofisica de Canarias press release, 2 June 2021.
Ignacio Negueruela (Universidad de Alicante, Spain)
Javier Méndez (ING PR Officer)
About the Isaac Newton Telescope
Based on observations made with the Isaac Newton Telescope (INT) operated on the island of La Palma by the Isaac Newton Group of Telescopes (ING) in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias (IAC). The ING is funded by the Science and Technology Facilities Council (STFC-UKRI) of the United Kingdom, the Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO) of the Netherlands, and the IAC in Spain. IAC's contribution to ING is funded by the Spanish Ministry of Science, Innovation and Universities.