A Hungarian-US team of astronomers have found what appears to be the largest feature in the observable universe: a ring of nine gamma ray bursts – and hence galaxies - 5 billion light years across. The scientists, led by Prof Lajos Balazs of Konkoly Observatory in Budapest, report their work in a paper in Monthly Notices of the Royal Astronomical Society.
Gamma-ray bursts (GRBs) are the most luminous events in the universe, releasing as much energy in a few seconds as the Sun does over its 10 billion year lifetime. They are thought to be the result of massive stars collapsing into black holes. Their huge luminosity helps astronomers to map out the location 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 (the sample is listed in the Gamma Ray Burst Online Index). They 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 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.
Most current models indicate that the structure of the cosmos is uniform on the largest scales. This 'Cosmological Principle' is backed up by observations of the early universe and its microwave background signature, seen by the WMAP and Planck satellites. Other recent results and this new discovery challenge the principle, which sets a theoretical limit of 1.2 billion light years for the largest structures. The newly discovered ring is almost five times as large.
