The Biggest Structure in the Universe
The universe contains structures on every level, from the organisation of a cell to the orbits of our solar system to the collection of stars that make up our galaxy. Even galaxies are arranged into clusters, bound by gravity. We belong to a group of around 50 galaxies called the Local Group—but our local neighbourhood is just a speck in the structure of the universe.
Galaxies are organised into structures called filaments, connected like a web of bright neurons and synapses. The largest filament we know of is called the ‘Hercules-Corona Borealis Great Wall’, a truly vast collection of galaxies about 10 billion light years away, in the direction of the constellations Hercules and Corona Borealis.
This Great Wall was discovered in November 2013 by mapping the locations of gamma ray bursts, which are brief but awesomely energetic bursts from the collapse of massive stars in distant galaxies. Larger stars tend to form in regions that contain a large amount of material, so when researchers realised that this particular region had a disproportionate number of gamma ray bursts all clustered together, they realised that it must indicate a supermassive structure.
Using the locations of the gamma ray bursts, researchers estimate the region spans 10 billion light years across. This means light would take about two thirds of the age of the universe to travel from one end to the other.
The Hercules-Corona Borealis Great Wall is over double the size of the next contender (a group of quasars spanning 4 billion light years). It’s actually so big it’s inconvenient—current cosmological theory tells us that matter in the universe should be fairly evenly distributed on a large scale, so the mere existence of the Great Wall is a challenge.
So far, researchers have no idea how a structure of this size evolved, but maybe the answer to that will help solve the puzzle it poses to cosmology.
(Note: The first image above is a Hubble mosaic of a huge galaxy cluster called MACS J0717.5+3745, which the Hercules–Corona Borealis Great Wall may be similar to.)
