Astronomers have discovered a huge galactic supercluster located about 4 billion light-years from Earth. And this supercluster is not only one of the largest cosmic structures ever discovered, it is also the most distant supercluster ever found and investigated.
On the scale of the universe, everything is relative. It may seem to you that the world in which we live is simply incredibly huge, but it is only a small part of an even larger structure - the solar system - which, in turn, looks like only an insignificant grain of sand against the backdrop of our Milky Way galaxy. But this is far from the limit. Galaxies have the property of being attracted to each other, forming the so-called galactic groups, or clusters. And then there are superclusters that unite several more compact clusters of galaxies under them.
And just one of these galactic superclusters was discovered by a team of astronomers from India, having determined the presence of a previously unknown very dense cluster of galaxies, which was named after the Indian river Saraswati.
The Saraswati supercluster, discovered by researchers at the Inter University Center for Astronomy & Astrophysics (IUCAA), is truly enormous. It stretches for about 600 million light years, and its mass, according to preliminary calculations, may be more than 20 million billion Suns.
Even if we discard the gigantic size and mass, what makes this discovery interesting is that in fact astronomers have not yet discovered so many of these superclusters, which allows Saraswati to essentially join a kind of elite club.
“Previously, not so many superclusters of comparable size were discovered. These include, for example, the Shapley supercluster or the Sloan Great Wall,”astronomers Joydip Bagchi and Shishir Sankhyan commented.
But what distinguishes Saraswati's super fulfillment from them is that, unlike the latter, located in relative proximity to us, Saraswati is located about 4 billion light years from Earth.
“This is the first time that we have been able to detect an overshoot so far away from us. Even Shapley is about 8-10 times closer to us,”says Somak Raishaudhuri, one of the Indian team members who also previously contributed to the discovery of the Shapley supercluster.
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The two most massive clusters of the Saraswati supercluster
Astronomers have discovered the Saraswati supercluster by analyzing data collected by the Sloan Digital Sky Survey project. According to scientists, this supercluster consists of at least 43 galactic groups and clusters, for a total of about 400 different galaxies. Since Saraswati is so far from Earth, this means that his light, before scientists noticed him, had to overcome an enormous distance, having spent several billion years on it. Calculations say that the appearance of the supercluster, which appears to us now, was in fact exactly the same when the age of the universe was 10 billion years.
This glimpse into the past can help us understand how such massive cosmic superstructures are formed, as well as learn more about the conditions in the early Universe they had to do it.
"Since the formation of such an immense cosmic structure occurs very slowly, several billion years, it carries a kind of record of the entire history of its formation," says Bagchi.
It can also be noted that the presence of the Saraswati supercluster, 4 billion light years away, was a real surprise for scientists. Because if we take into account our current understanding of galactic evolution, such gigantic cosmic structures simply did not have enough time to form into something like this when the universe was only 10 billion years old. This means that our new theoretical concepts of dark energy and dark matter, the opinion of which among scientists is still not unambiguous, in fact could play an important role here.
“Theory has always been hit by the reality of nature. The balance of dark matter and dark energy is indeed capable of producing giant structures, but clusters of this size are still a mystery to us,”says Raishaudhuri.
In general, despite the discovery of such a giant supercluster, somewhere there may be even larger cosmic structures awaiting their discovery.
Nikolay Khizhnyak
