A group of astronomers from Hungary and Maerics led by Prof Lajos Balazs, have found what may be the largest feature in the known universe: a giant ring of nine galaxies 7 billion light years away and 5 billion light years wide. For a comparison, that’s about 50,000 times bigger than the Milky Way, or more than one-ninth the size of the observable universe.
The ring was revealed by nine Gamma-Ray Bursts (GRB) originating from the nine galaxies. Gamma-ray bursts are the brightest objects in the universe, releasing as much energy in a few seconds as the sun does over its 10 billion year lifetime. They are supposed to be the outcome of massive stars collapsing into giant black holes. Their enormous glow helps astronomers to mark the position of distant galaxies, something the team exploited. The GRBs that make up the newly discovered ring were observed using a variety of space- and ground-based observatories.
A GRB is an intense flash of gamma rays caused by a supernova, the dramatic death of a fiery star, and thus their detection indicates the presence of a galaxy. Aside from their spectacular deaths, they also help astronomers to measure the distance of other galaxies. They appear to be at very similar distances from us – around 7 billion light years in a circle more than 70 times the diameter of the full Moon, researchers said.
They seem to be at much related distances from us – around 7 billion light years – in a ring 36° across on the sky, or more than at least 70 times the diameter of the Full Moon. This suggests that this circle is more than 5 billion light years across, and according to Prof Balazs there is merely a 1 in 20,000 chance of the GRBs being in this spreading by chance. In this case, the observed GRB’s indicate that the nine galaxies are positioned in a ring shaped like a shell.
While it is not one physical whole structure, the Hungarian-American team who made the discovery think the nine galaxies are gravitationally bound to each other – just as our Local Group contains the Milky Way and a few dozen other galaxies. All the GRBs studied by a variety of observatories are about 7 billion light-years away from Earth, suggesting that we are seeing the structure “face on.” Alternatively, we may be seeing a projection of a “sphere.” But there’s one problem, the structure, if confirmed, would break our current models of how large things can be; a previous theoretical limit stood at 1.2 billion light-years. On large scales, the cosmos should be uniform and not have structures like this.
A spheroidal ring projection would reflect the strings of clusters of galaxies observed to border voids in the cosmos; voids and string-like creations are seen and projected by several models of the cosmos. The recently discovered ring is nonetheless at least ten times bigger than known voids. Prof Balazs says “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 wants 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 research was published in the journal Monthly Notices of the Royal Astronomical Society.