A team of Indian astronomers has identified one of the largest known structures in the nearby Universe, a colossal supercluster of galaxieslocated 4 billion light-years away in the constellation Pisces. They have named it Saraswati , name of the Indian goddess of knowledge, music, art, wisdom and nature, muse of all creativity, and occupy an extent as huge as 600 million light years.
Large-scale structures of the Universe are hierarchically assembled, with galaxies, along with associated gas and dark matter, grouped in clusters, which are organized with other clusters, smaller clusters, filaments, leaves and large empty regions ) In a pattern called “cosmic tissue” encompassing the observable Universe.
Superclusters are the largest coherent structures in the cosmic network. A supercluster is a chain of galaxies and galaxy clusters, joined by gravity, which often extends to several hundred times the size of galaxy clusters, consisting of tens of thousands of galaxies. The newly discovered Saraswati, for example, spreads on a scale of 600 million light-years and can contain a mass equivalent to more than 20,000 million suns. The density of its galaxies is very high and the typical size of one of them is of about 250,000 light-years.
When astronomers look away, they see the Universe a long time ago, since the light takes time to reach us. For this reason, Saraswati is observed as it was when the Universe was 10.00 billion years old.
Rethinking the Big Bang
The popular Cold Dark Matter (CDM) model of Universe evolution says that small structures like galaxies were first formed and then congregated into larger structures. Most forms of this model do not predict the existence of large structures such as the Saraswati supercluster within the current age of the Universe. The discovery of these extremely large structures forces astronomers to rethink popular theories of how the Cosmos acquired its present form, starting from a more or less even distribution of energy after the Big Bang.
In recent years, the discovery that dark energy, believed to behave very differently from gravitation, dominates the present universe, could play a role in the formation of these structures.
It is believed that galaxies are formed primarily in the filaments and leaves that are part of the cosmic tissue, and many of the galaxies travel along these filaments, ending in the abundant clusters, where the tight environment disconnects their star formation and Aid in the transformation of the blue spiral galaxies into red ellipticals. Since there is an extensive variation of environments within a supercluster, galaxies travel through these varied environments during their “life”. To understand their formation and evolution, it is necessary to identify these superclusters and study closely the effect of their environment on galaxies.