The Great Wall of the Universe

The universe is tremendously large, spreading across billions and trillions of light-years in all directions, with only a part of it being explored. Somewhere in the deepness of the universe, you can find unimaginably large structures which will make you feel insignificant in this universe - as we’re merely a species on a blue-dotted planet!


Astronomers have been actively looking for celestial objects scince years. The more time they’ve spent studying the universe, the bigger celestial bodies they’ve found. In the solar system itself, we’ve been dwarfed by Jupiter and the Sun. Our sun too looks puny when compared with other large stars like Betelguese & UY Scuti.


Moving up the list of large cosmic objects we have galaxies and then blackholes, especially supermassive black holes which are present at the center of each galaxy. Then there are galaxies and nebulae. Galaxies are further bound by gravity and these structures are called galaxy clusters. Initially, astronomers thought that galaxy clusters were the largest structures in the universe. But then they found galaxy superclusters, which are galaxy clusters further bound by gravity.


The first map of galaxy supercluster Laniakea, the home of Milky Way galaxy and many others. Image Credit: Nature video

What is the largest structure in space?


In 2013, when scientists were looking for an extremely rare phenomenon called gamma-ray bursts, they came across the largest structure in the universe - The Hercules Corona Borealis Great Wall. It is a giant sheet-like structure formed by a huge cluster of galaxies, spreading across 10 billion light-years in length (which is 10% of the diameter of the observable universe!). The enormous size of this structure implies that it was formed only 4 billion years after the Big Bang!


Does the Great Wall of the Universe really exist?

Gamma-rays are the strongest type of radiation in the electromagnetic spectrum. They are produced only in the event of explosive death of a star, collision of neutron stars or matter spun around by a black hole.


Astronomers study these gamma-ray bursts because they help them locate giant structures in the universe. In 2013, scientists recorded an unusually high volume of gamma-ray bursts in the direction of Hercules and Corona Borealis constellations. When they found the structure to spread across 10 billion light-years they were themselves doubtful about this discovery.


“I would have thought this structure was too big to exist. Even as a co-author I still have my doubts”, said Jon Hakkila, the co-author of this study.


On doing the calculations, they found that the chances of seeing a random number of gamma-ray bursts in that location are very less - far less than 1 in 100. So the researchers believed that the structure exists.


Jon further added, “There are other structures that appear to violate universal homogeneity: the Sloan Great Wall and the Huge Large Quasar Group are two. Thus, there may very well be others, and some could indeed be bigger. Only time will tell”.


To learn more on this, watch this video by SEA on YouTube.




References:

https://www.space.com/33553-biggest-thing-universe.html

https://www.sciencefocus.com/space/what-is-the-largest-object-in-the-universe/

https://www.scienceabc.com/nature/universe/what-is-the-biggest-thing-in-the-universe.html#a-structure-so-big-that-it-shouldn-rsquo-t-exist



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