“The Hindu religion is the only one of the world”s great faiths dedicated to the idea that the Cosmos itself undergoes an immense, indeed an infinite, number of deaths and rebirths. It is the only religion in which time scales correspond to those of modern scientific cosmology,” hailed renowned American astronomer and Pulitzer Prize-winning author Carl Sagan in his best seller ‘Cosmos’. The historical timeline of the major achievements in science bears testimony to the glorious past Indian astronomy. After a certain interval of time, the latest developments in the realm of Indian astronomical research signify that India is on right direction in pursuit of regaining the lost glory. A team of astronomers from the Inter University Centre for Astronomy and Astrophysics (IUCAA), and Indian Institute of Science Education and Research (IISER), both in Pune, and members of two other Indian universities, have discovered an ‘extremely large supercluster of galaxies’, one of the largest known structures in the nearby Universe, and named it after ‘Saraswati’. The discovery has not only brought glory to the nation but also scripted a new chapter in the history of astronomical research in India. This project was supported by the University Grants Commission of India, through its funding of IUCAA, and the Indo-French Centre for the Promotion of Advanced Research (CEFIPRA) programme.
Shishir Sankhyayan, a PhD student at IISER, Pune, is a co-author of the research paper on “Saraswati Supercluster Discovery” which has been published in the latest issue of The Astrophysical Journal, the premier research journal of the American Astronomical Society. He spoke to Ganesh Krishnan R, Sub-Editor of Organiser, about the discovery of ‘Saraswati’ and its significance. Excerpts:
Congratulations for the great achievement. I think it is for the first time Indian astronomers made such a remarkable achievement of discovering a supercluster of galaxies. How do you see it?
Thank you. In fact, Somak Raychaudhury, who was then a PhD student at the University of Cambridge, had discovered a supercluster in 1989. Interestingly, now he is the Director of IUCAA, Pune. He discovered the first massive Supercluster of galaxies. So you can say this is the first such discovery from India.
What is the significance of this discovery?
In the evolution of our universe, the dark matter and dark energy govern how the universe evolves, how galaxies are formed and evolved. Everything is governed majorly by these two forces. In the models of the universe and structure, the general model or the current model says that you cannot have these kinds of massive and large superclusters in our universe. But we have found them. Right now, we have very less number of them, three or four. But we are finding them years after years. So we need to rethink or need empirical simulations that can validate the existing models. Our work will help to shed light on the perplexing questions like how such extreme large scale, prominent matter-density enhancements had been formed billions of years ago when the mysterious Dark Energy had just started to dominate structure formation.’ So to understand dark energy, it is important to understand dark matter.
| The large-scale structure of the Universe is made up of voids and filaments that can be broken down into superclusters, clusters, galaxy groups, and subsequently into galaxies. Supercluster: 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. Dark Energy: an unknown form of energy which is hypothesised to permeate all of space, tending to accelerate the expansion of the universe. Dark Matter: A hypothetical type of matter distinct from baryonic matter (ordinary matter such as protons and neutrons), neutrinos and dark energy. Dark matter has never been directly observed; however its existence would explain a number of otherwise puzzling astronomical observations. Light Year: A unit of astronomical distance equivalent to the distance that light travels in one year, which is nearly 6 million million miles. |
Why the name ‘Saraswati’?
Because the supercluster has been discovered on the Indian soil, we wanted to give an Indian name. Also, because it is like a river of galaxies and super clusters in the universe. Just like Akash Ganga, the milky way, as it had been named after the river Ganga, we wanted to name it after the river Saraswati. Saraswati is also worshipped as the goddess of knowledge, wisdom and all creativity.
Could you please give details about the ‘Saraswati’ like how old it is and how far it is away from us?
It is not a single galaxy. It is a cluster of galaxies. There are tens of thousands of galaxies in this supercluster. And this supercluster is 4 billion light years away from the earth, from the milky way, you can say. It is located in the direction of constellation Pisces. 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.
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Inter University Centre for Inter University Centre for Astronomy and Astrophysics (IUCAA) was set up in 1989 by the University Grants Commission (UGC) to promote the nucleation and growth of active groups in astronomy and astrophysics at Indian universities. IUCAA aims to be a centre of excellence within the university sector for teaching, research and development in astronomy and astrophysics. One important component of IUCAA”s academic activities is the Associateship Programme, under which a faculty member of an Indian university or a post-graduate department in a college can visit IUCAA for periods of short and long durations over a span of three years to develop his or her interest and expertise in astronomy and astrophysics. They can and often do bring their UG or PG students with them to take part in the research. |
A few words about the team behind this research.
The lead author or the team leader of the project is Joydeep Bagchi from IUCAA, then myself, Prakash Sarkar from NIT Jamshedpur, Somak Raychaudhury the Director of IUCAA, Joe Jacob from Newman College, Kerala and Pratik Dabhade from IUCAA. We were six team members to discover this supercluster.
As far as astronomical research is concerned, India has a very rich past. Being a part of this great discovery which brought a glory to India, how do you look upon it?
India has a very rich heritage in astronomical research. In ancient India, there were many astronomers like Aryabhata and many scientists or thinkers who contributed a lot to Mathematics and Astronomy. After that, there were many scientists and astronomers who contributed to astrophysics. So I think now it is proved that we are achieving something on the global level; that is good.
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