Ring of GRBs hint at existence of largest ever feature in the observable universe

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Largest ever feature in the observable universe found
An image of the distribution of GRBs on the sky at a distance of 7 billion light years, centred on the newly discovered ring. The positions of the GRBs are marked by blue dots and the Milky Way is indicated for reference, running from left to right across the image. Credit: L. Balazs.

A team of international researchers have stumbled upon what they believe is the largest known feature in the observable universe – a ring of galaxies 5 billion light years across.

Led by Prof Lajos Balazs of Konkoly Observatory in Budapest, a team of Hungarian-US astronomers mapped the location of 9 gamma ray bursts using their huge luminosity and in the process mapped out the location of distant galaxies.

Researchers observed the GRBs using a variety of space- and ground-based observatories. Researchers say that from their analysis, they all appear to be at very similar distances from us – around 7 billion light years – in a circle 36° across on the sky, or more than 70 times the diameter of the Full Moon.

This, researchers say, implies that the ring is more than 5 billion light years across, and according to Prof Balazs there is only a 1 in 20,000 probability of the GRBs being in this distribution by chance.

According to most of the current models that are used to determine the structure of universe, cosmos is uniform on the largest scales. Previous studies have backed up this ‘Cosmological Principle’ by observations of the early universe and its microwave background signature, seen by the WMAP and Planck satellites.

But there have been a few recent studies, along with this one led by Prof Balazs that challenge the principle, which sets a theoretical limit of 1.2 billion light years for the largest structures. Based on the observations made by Prof Balazs’ team, the newly discovered ring is almost five times as large.

“If the ring represents a real spatial structure, then it has to be seen nearly face-on because of the small variations of GRB distances around the object’s centre. The ring could though instead be a projection of a sphere, where the GRBs all occurred within a 250 million year period, a short timescale compared with the age of the universe”, Prof Balazs says.

A spheroidal ring projection would mirror the strings of clusters of galaxies seen to surround voids in the universe; voids and string-like formations are seen and predicted by many models of the cosmos. The newly discovered ring is however at least ten times larger than known voids.

Prof Balazs comments: “If we are right, this structure contradicts the current models of the universe. It was a huge surprise to find something this big – and we still don’t quite understand how it came to exist at all.”

The team now want to find out more about the ring, and establish whether the known processes for galaxy formation and large scale structure could have led to its creation, or if astronomers need to radically revise their theories of the evolution of the cosmos.

The study is published in Monthly Notices of the Royal Astronomical Society.