Astronomers spot ‘supercluster’ of galaxies nearly as old as the Big Bang

A new discovery supercluster of galaxies is so distant that astronomers say its light has been traveling for more than 12 billion years to reach telescopes on Earth. But this cluster, named SPT2349-56, is gigantic and so old that it’s actually classified as a galaxy protocluster, meaning it could be one of the first large galaxy clusters in our universe. It is also one of the most active known protoclusters in star formation.

The SPT2349-56 supercluster was discovered in the submillimeter band by the South Pole Telescope. Astronomer Matthew Ashby of the Harvard Smithsonian Center for Astrophysics (CfA) was one of the team members who made follow-up observations with the Gemini Observatory, the Hubble Space Telescope and the Spitzer Space Telescope to conduct deep observations at optical and infrared wavelengths.

SPT2349-56 hosts hundreds of galaxies, including more than thirty sub-millimeter luminous galaxies and dozens of other spectroscopically confirmed luminous and/or star-forming galaxies. Although it is a cluster of galaxies from the early Universe, galaxy mergers and active star formation are occurring at an incredible rate, producing more than ten thousand stars per year. Astronomers have said that one of its brightest sources appears to be the merger of more than twenty galaxies.

One of the purposes of the observations was to try to obtain the stellar mass of the system; however, the team was unsuccessful. They said that not knowing the system’s stellar mass made it impossible, for example, to know whether the huge starburst they were observing was the result of extraordinary efficiency or simply because the system was extremely large.

A typical supercluster contains all groups of galaxies and clusters of galaxies that appear to be associated with each other by mutual gravitational attraction and contains approximately one quadrillion solar masses. Astronomers have estimated that there are 130 superclusters located within 1.3 billion light-years of the Milky Way. Another supercluster in the early Universe that was detected by the South Pole Telescope in 2010 weighs around 800 trillion suns and contains hundreds of galaxies.

The astronomers have found that the rate of star formation in this primordial cluster compares similarly to the rate of star formation measured in nearby regular galaxies, and they therefore conclude that star formation processes at the work in this early universe are similar to those that came later in the local universe. They found that this cluster does, however, have a molecular gas deficit, suggesting that activity is nearing the end of this tumultuous phase as the stars’ raw material dissipates.

The astronomers said they predicted the central galaxies of this supercluster would quickly merge into one of the brightest clusters of galaxies and that their observations would provide a direct view of the early mechanisms of formation of this class of objects.

A false-color image of the far-infrared emission from a massive protocluster of galaxies (in the circle) dating to the time around 1.4 billion years after the big bang. The astronomers made deep optical and infrared observations of the complex and concluded that the star-forming processes at work, while unusually active, appear to generally follow the same processes seen in our galaxy.NASA/ESA/Herschel; Miller et al.

This article was originally published on Universe today by Nancy Atkinson. Read the original article here.

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