July 14 (UPI) -- Indian astronomers have surveyed a giant galactic supercluster located 4 million light-years from Earth. The cluster of galaxies, found in the direction of the Pisces constellation, is one of the most massive large-scale structures in the universe.
The cosmic web describes the organization of all matter in the universe, including galaxies, gas, and dark matter. The structure is organized into clusters, which can be grouped into large clusters, each connected by filaments of dark matter. In-between the superstructures lie vast voids.
Superclusters are comprised of galaxies and galaxy clusters bound by gravity. They are the largest coherent structures in the cosmic web.
The Saraswati supercluster, described this week in the Astrophysical Journal, stretches 600 million light-years across. It comprises a total mass of more than 20 million billion suns. Being so far away, the Saraswati supercluster offers astronomers a window into the early universe, revealing the cosmos as it was when the universe was 10 billion years old.
Most models of cosmic evolution, including "cold dark matter" models, fail to to predict the formation of superstructures like Saraswati. Cold dark matter models posit that single galaxies become bound together by gravity over time.
Observations of superclusters like Saraswati suggest dark energy may play a role equal to gravity in inspiring the evolution of the cosmic web's largest structures.
Astronomers hope that by studying the influence of superstructures on individual galaxies, they can come to better understand the formation of the cosmic web and the evolution of the universe.
''We were very surprised to spot this giant wall-like supercluster of galaxies, visible in a large spectroscopic survey of distant galaxies, known as the Sloan Digital Sky Survey," astronomer Somak Raychaudhury, director of the Inter University Centre for Astronomy & Astrophysics in Pune, India, said in a news release. "This supercluster is clearly embedded in a large network of cosmic filaments traced by clusters and large voids."
Most other superclusters, such as the Shapley Concentration and the Sloan Great Wall, are located in the nearby universe.
"The Saraswati supercluster is [the] far more distant one," Raychaudhury said. "Our work will help to shed light on the perplexing question: how such extreme large scale, prominent matter-density enhancements had formed billions of years in the past when the mysterious dark energy had just started to dominate structure formation.''