What are galaxy clusters?
- Galaxies are like the building blocks of the universe and they contain a huge number of stars (like 100 billion at a count).
- Galaxy groups can have three to 20 galaxies whereas the galaxy clusters can have several hundred galaxies.
- Superclusters are clusters of clusters and the number can vary from two clusters to many clusters.
- The recently discovered supercluster Saraswati has 42 clusters.
What are superclusters?
- These are the largest coherent structures seen in the universe.
- Firstly there are clusters of galaxies together with associated gas and dark matter.
- Large groups of such clusters, linked by filaments, separated by voids together form the superclusters.
- The first such large supercluster to be discovered was the Shapley supercluster.
- The Milky Way is part of a supercluster called the Laniakea Supercluster. It was announced in 2014.
How does the Saraswati supercluster compare with the Milky Way?
- The newly discovered Saraswati supercluster is 600 million light years across.
- The Milky Way is 150,000 light years across.
Where does the supercluster Saraswati lie in the sky?
- The supercluster Saraswati lies in the Stripe 82 of the Sloan Digital Sky Survey.
- It is about 4000 million light years away from us.
- It is in the constellation of Pisces.
What is “Stripe 82 region of SDSS”?
- SDSS stands for the Sloan Digital Sky Survey, which is an ambitious plan to make a digital 3D map of the universe.
- It was started in 2000 and over eight years it has mapped more than a quarter of the sky.
- In its third phase, SDSS-III, it produced a map of the North galactic cap which stretched to 7500 square degrees and of three stripes in the South Galactic Cap which added to 740 square degrees. The central stripe is known as Stripe 82.
(There’s no need to mug up mapping details, it is only for your understanding.)
Is Saraswati the first supercluster that Indians have discovered?
- Professor Somak Raychaudhury had discovered a supercluster and it was named “Shapley Supercluster,” after the American astronomer Shapley who first coined the term cluster.