Astronomers discover gigantic superclusters

Wall-like matter accumulation belongs to the largest known structures of the cosmos

The elongated Saraswati supercluster (center) resembles a denser wall © Bagchi et al. / IUCAA
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Cosmic Giant: Astronomers have discovered one of the largest known structures in the cosmos - an elongated supercluster that spans at least 650 million light-years and includes billions of solar masses of galaxies and galaxy clusters. How did this Saraswati supercluster originate, the astronomers do not know. But they suspect that the mysterious Dark Energy played an important role.

The matter is not evenly distributed in the universe, but forms large-scale structures - galaxy clusters, filaments and so-called superclusters. The latter are huge structures in which tens of thousands of galaxies move together. Our Milky Way also belongs to such a supercluster, the approximately 520 million light-years Laniakea.

"Like a cosmic wall"

However, astronomers around Joydeep Bagchi from the Inter-University Center for Astronomy and Astrophysics in Pune, India have discovered an even larger supercluster. They came across this large structure as they evaluated data from the Sloan Digital Sky Survey. At about four billion light-years away they noticed an enormous collection of galaxies and galaxy clusters.

"We were very surprised to discover this gigantic supercluster resembling a huge wall, " says Bagchi. The supercluster stretches over at least 650 million light-years and includes tens of thousands of galaxies. In its densest region, they form 48 galaxy clusters, 23 of which are extremely massive. More clumps of co-moving clusters are loosely distributed and the central "wall" around, as the researchers report.

Unusually large and massive

As the astronomers discovered, the 43 largest galaxy clusters of the new supercluster already contain around 20 quadrillion solar masses. "This indicates an unusually large concentration of mass in the supercluster, " the researchers said. "He is one of the largest and heaviest known super clusters in the near universe." Display

Because of its river-like structure, the astronomers baptized the supercluster after the ancient Indian river god Sarawati. historical

Astronomers have christened the new superclass Saraswati - after the Indian goddess, who is considered to be the guardian of the celestial rivers, and the goddess of wisdom and nature. "The Sanskrit name also means 'ever-flowing stream with many pools', " explain Bagchi and his colleagues. "This describes quite well this large, filamentous structure in the constellation fish, which consists of many clusters and groups that move together and merge together."

How did he come into being?

Exceptional and exciting is the newly discovered Saraswati supercluster not only because of its sheer size, but also because of its age: in contrast to the two similar sized superclusters Shapley and Sloan Great Wall is not located in our cosmic neighborhood, but four billion light-years away. He is thus significantly older than her.

The exciting thing about it: "Large-scale structures of this size are developing very slowly, " explain the researchers. The existence of the Saraswati supercluster some four billion years ago indicates that these enormous collections of matter have very old roots. But so far astronomy can not explain how the initially more evenly distributed primal matter could produce such extreme mass accumulations.

Is dark energy involved?

So far, researchers have suggested in the more recent, more recent, superclusters that the increasingly dominant influence of the mysterious dark energy might play a role. The dark energy is considered to be the antagonist of gravity and the force that drives the expansion of the universe. "It could also influence the development of turbulence in matter density, " explains Bagchi.

The Saraswati supercluster is so exciting because it developed shortly after a decisive change in the balance of forces in the cosmos: About six billion years ago, the influence of dark energy gained the upper hand over the gravitation since accelerated Expansion of the universe. Possibly, this change also played a crucial role in the formation of the supercluster.

Interesting Voids

A first indication of Dark Energy involvement is seen by astronomers in a conspicuous heap of large voids around the Saraswati supercluster. Such empty regions in the cosmos are more strongly under the influence of the dark energy and therefore expand very fast. According to the researchers, they could push the galaxies and galaxy clusters together at their edges, thus favoring the formation of super clusters.

Astronomers have recently discovered a similarly repulsive region of space in our cosmic neighborhood: the so-called "dipole repeller" pushes the Milky Way and the Local Group away from each other, influencing their movements Surprisingly strong. (Astrophysical Journal, 2017; arXiv: 1707.03082)

(Inter-University Center for Astronomy and Astrophysics, 17.07.2017 - NPO)