Indian scientists discover ‘Saraswati’, a supercluster of galaxies

Indian scientists have discovered Saraswati, a large supercluster of galaxies located in the direction of the constellation Pisces, and at a distance of 4,000 million (400 crore) light years away from Earth.

A team of astronomers from the Inter-University Centre for Astronomy and Astrophysics (IUCAA) and Indian Institute of Science Education and Research (IISER), Pune, and members of two other Indian universities, have discovered this supercluster of galaxies. 

Supercluster is a chain of galaxies and galaxy clusters, bound by gravity, often stretching to several hundred times the size of clusters of galaxies, consisting of tens of thousands of galaxies. This newly-discovered Saraswati supercluster, extends over a scale of 600 million light years and may contain the mass  equivalent of over 20 million billion suns.

The discovery will be published in the latest issue of The Astrophysical Journal, the premier research journal of the American Astronomical Society. 

Joydeep Bagchi from IUCAA, the main author of the paper and co-author Shishir Sankhyayan (PhD scholar at IISER, Pune) said, ‘’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. This supercluster is clearly embedded in a large network of cosmic filaments traced by clusters and large voids. “ 

They stated that previously only a few comparatively large superclusters have been reported, for example the Shapley Concentration or the Sloan Great Wall in the nearby universe, while the Saraswati supercluster is far more distant one. 

“Our work will help to shed light on the perplexing question of 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,’’ they added. 

Officials also stated that to understand galaxy formation and evolution, one needs to identify these superclusters and closely study the effect of their environment on the galaxies. This is a new research area and the discovery will enhance this field of research. 

They added that when astronomers look far away, they see the universe from long ago, since light takes a while to reach us. The Saraswati supercluster is observed as it was when the Universe was 10 billion years old. 

 Officials from IUCAA said the paper was special because it is a direct product of IUCAA’s associateship programme. While two of the authors are faculty members of IUCAA namely Prof. Joydeep Bagchi and Prof. Somak Raychaudhury, Director IUCAA), the other authors are Shishir Sankhyayan - PhD student at Indian Institute of Science Education and Research (IISER) Pune and regular visiting student at IUCAA, Pratik Dabhade - Research Fellow at IUCAA, Joe Jacob - Department of Physics, Newman College, Thodupuzha, Kerala (IUCAA Associate) and Prakash Sarkar - Dept. of Physics, National Institute of Technology, Jamshedpur (ex- IUCAA Postdoctoral Fellow).