What is a galaxy clusters ?
A galaxy cluster, or cluster of galaxies, is a structure that consists of anywhere from hundreds to thousands of galaxies that are bound together by gravity.
What are superclusters ?
A supercluster is a large group of smaller galaxy clusters or galaxy groups, which is among the largest-known structures. They are the largest known gravitationally bound structures in the universe.
A group of Indian astronomers have discovered a massive supercluster of galaxies, and have named it Saraswati. The supercluster is about 4 billion light years away and spreads about 600 million light years across. This makes it one of the largest superclusters to be discovered and also the furthest. The first supercluster of galaxies, the Shapley Supercluster, was discovered in 1989, and the second, the Sloan Great Wall in 2003. The Milky Way galaxy is part of the Laniakea Supercluster, which was discovered in 2014.
Significance of the discovery
There are thin “filaments” that connect galaxies, forming a cosmic web, and there are large voids in between. The current belief is that infant galaxies form in these filaments and then drift to the intersections of the filaments where they grow. The Saraswati supercluster could challenge this premise, because it had formed so early and building such a big structure far back might have been difficult.
- When sighting a supercluster of galaxies 4 billion light years away, the observer is looking back about 4 billion years.
- A light year is the distance travelled by light in one year.
- Given the belief that the universe is 13.8 billion years old, the discovery implies that such a huge structure existed even when the universe was just about ten billion years old.
- This raises questions about the formation of large structures and the nature of the universe.
Source : The Hindu
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