Saraswati - A Supercluster Galaxy

Why in news?

Indian astronomers discovered Supermega River of galaxies.

What is it?

• A team of Indian astronomers has identified a cosmic behemoth – a supercluster of galaxies – about 4 billion light- years away from us
• The new discovery has been named saraswati.
• The supercluster spans over 650 million light years in its expanse, containing over 10,000 galaxies in 42 clusters.

Why is it important?

• The discovery is forcing astronomers to rethink about early stages of the evolution of the universe.
• It also provides vital clues about the mysterious dark matter and dark energy.
• The saraswati supercluster clearly stands out in the sky as an especially rare, and possibly among the mega superclusters exceeding 500 million light years in size.
• A large scale structure this massive evolves very slowly.
• Therefore it may reflect the whole history of galaxy formation and the primordial initial conditions that have seeded it.

How it challenges current model?

• The long-popular “cold dark matter” model of evolution of universe predicts that small structures like galaxies form first, which congregate into larger structures.
• The existence of large structures such as the “Saraswati Supercluster” that evolved as early as 10 billion years since the big bang is a challenge to this model.
• Thus forces astronomers into re-thinking popular theories of how the universe got its current form.
• 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 dominated structure formation.

What are super clusters?

• It is a large group of smaller galaxy clusters or galaxy groups
• It is among the largest-known structures of the cosmos.
• The Milky Way is part of the Local Group galaxy cluster (that contains more than 54 galaxies), which in turn is part of the Laniakea Supercluster.
• This supercluster spans over 500 million light-years, while the Local Group spans over 10 million light-years.
• The number of superclusters in the observable universe is estimated to be 10 million.

What is Sloan Digital Sky Survey?

• The Sloan Digital Sky Survey or SDSS is a major multi-spectral imaging and spectroscopic redshift survey by USA

• It is an ambitious plan to make a digital 3D map of the universe.
• It started in the year 2000, and over eight years it mapped more than a quarter of the sky.
• It has mapped nearly 930,000 galaxies. The SDSS has found nearly 50 million galaxies so far.
• In its third phase, SDSS-III, which started in 2008 and ended in 2014, gave out sets of data that were released in 2011, 2012 and 2013.
• It produced a map of the North galactic cap and of three stripes in the South Galactic Cap and the central stripe is known as Stripe 82.