From IAC Institute of Astrophysics of the Canary Islands [Instituto de Astrofísica de Canarias] (ES) : “Astronomers discover a massive star cluster of intermediate age in the constellation Scutum”

Instituto de Astrofísica de Andalucía

From IAC Institute of Astrophysics of the Canary Islands [Instituto de Astrofísica de Canarias] (ES)


Ricardo Dorda

View of the cluster if the contamination of stars and dust that hides it could be removed. Credit: Gabriel Pérez Díaz, SMM (IAC).

An international team of astrophysicists led by the Stellar Astrophysics Group of the University of Alicante [Universitat d’Alacant[univeɾsiˈtad dalaˈkant] (ES), the Instituto de Astrofísica de Canarias (IAC), and the University of Valparaíso [Universidad de Valparaíso] (CL) has discovered a massive cluster of stars of intermediate age in the direction of the Scutum constellation. This object, which has been named Valparaíso 1, lies some seven thousand light years away from the Sun, and contains at least fifteen thousand stars. To detect it, observations have been combined from ESA’s Gaia satellite, and various ground-based telescopes, including the Isaac Newton Telescope at the Roque de los Muchachos Observatory (Garafía, La Palma, Canary Islands). The result has been published in MNRAS.

Open clusters are groups of stars which were born together, and move together, bound by gravity. This makes them natural laboratories for studying the physics and the lives of stars. The more stars there are in a cluster, the more useful it is, because the larger sample gives a better chance to find stars in less frequent evolutionary phases.

This is why astronomers are searching for the most massive clusters in our Galaxy, those with over ten thousand stars. Until twenty years ago it was thought that these are formed only in distant galaxies with exotic properties, but thanks to these searches now we know a dozen very young massive clusters (less than 25 million years old), and a few very old ones (thousands of millions of years old), which are descendants of former young clusters. But there are hardly any massive clusters known with intermediate ages, and it was not clear whether these do not exist, or whether they had not yet been found.

The newly discovered cluster, which they have called Valparaíso 1, is at some seven thousand light years from the sun, and contains at least fifteen thousand stars. Its unexpected discovery, in a well-explored part of the sky, suggests than many other massive clusters might be hidden in the very dense star fields, which observers find when looking towards the centre of our Galaxy.

“Valparaíso 1 contains dozens of stars sufficiently bright to be observable through an amateur telescope, but they are lost in the middle of a crowd of stars which don’t belong to the cluster, but which are in front of it or behind it, and which disguise the structure of the cluster”, explains Ignacio Negueruela, a researcher at the University of Alicante and the first author of the article.

“Previous searches tried to locate open clusters, but Valparaíso 1 does not look like a cluster similar to those which we usually find, and that is why it was not discovered before”, says Ricardo Dorda, an IAC researcher who is a co-author of the article.

The cluster was detectable thanks to the Gaia satellite of the European Space Agency (ESA), a space telescope which gives extremely accurate positions and distances of stars quite far away, and with this information we can measure the tiny motions across the sky shown by the stars over the years. Combining all of the information, we can detect clusters as groups of stars, which are at the same distance from us, and move together, groups of stars easier to detect using physics than just by looking at them on the sky. When the researchers had located this cluster, they used telescopes at the Carnegie Institution for Science (US) Las Campanas Observatory (CL) and the Isaac Newton Telescope (INT) at the Roque de los Muchachos Observatory (Garafía, La Palma, Canary Islands) to derive the physical properties of its stars.

See the full article here .


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IAC Institute of Astrophysics of the Canary Islands [Instituto de Astrofísica de Canarias] (ES) operates two astronomical observatories in the Canary Islands:

Roque de los Muchachos Observatory on La Palma
Teide Observatory on Tenerife.

The seeing statistics at ORM make it the second-best location for optical and infrared astronomy in the Northern Hemisphere, after Mauna Kea Observatory Hawaii (US).

The site also has some of the most extensive astronomical facilities in the Northern Hemisphere; its fleet of telescopes includes the 10.4 m Gran Telescopio Canarias, the world’s largest single-aperture optical telescope as of July 2009, the William Herschel Telescope (second largest in Europe), and the adaptive optics corrected Swedish 1-m Solar Telescope.

The observatory was established in 1985, after 15 years of international work and cooperation of several countries with the Spanish island hosting many telescopes from Britain, The Netherlands, Spain, and other countries. The island provided better seeing conditions for the telescopes that had been moved to Herstmonceux by the Royal Greenwich Observatory, including the 98 inch aperture Isaac Newton Telescope (the largest reflector in Europe at that time). When it was moved to the island it was upgraded to a 100-inch (2.54 meter), and many even larger telescopes from various nations would be hosted there.

Teide Observatory [Observatorio del Teide], IAU code 954, is an astronomical observatory on Mount Teide at 2,390 metres (7,840 ft), located on Tenerife, Spain. It has been operated by the Instituto de Astrofísica de Canarias since its inauguration in 1964. It became one of the first major international observatories, attracting telescopes from different countries around the world because of the good astronomical seeing conditions. Later the emphasis for optical telescopes shifted more towards Roque de los Muchachos Observatory on La Palma.