Mind Boggling Scales
Challenging our understanding of the scale of the universe, astronomers led by Dr Roger Clowes from University of Central Lancashire have identified the largest known structure in the universe. It’s a group of 73 quasars, so large that it would take a vehicle travelling at the speed of light some four billion years to cross it. This is mind boggling if you compare it to our galaxy’s Milky Way – a mere 100,000 light years across.

Quasars are the brilliant cores of galaxies, their intense light is fuelled by radiation blasts from materials as they are sucked into the massive black holes of the stars being formed. Since 1982 astronomers have found that quasars tend to group together in clumps or 'structures', forming large quasar groups (LQGs).

Challenging Einstein
The huge scale of this new LQG challenges a fundamental theory of cosmology, based on the work of Albert Einstein, that the universe looks the same to all observers when viewed on a large enough scale. Called Cosmological Principle, it has never been demonstrated through observation 'beyond a reasonable doubt'.

This is the second time that Dr Clowes has discovered the largest known structure in the universe. The first one was in 1991, a tough task given the technology at the time, but eventually he and his Chilean collaborator identified what has become known as the Clowes-Campusano Large Quasar Group. Then with the creation of the Sloan Digital Sky Survey (SDSS), which uses a telescope at Apache Point in New Mexico, whose data is freely available to the world, they were able to extend their research.

Analysing Deep Galactic Data
Clowes explains, ‘we take the data from the SDSS and use computer algorithms to look for quasars that connect on a specified distance to the nearest neighbour. We used the data to rediscover the Clowes-Campusano LQG and another one nearby (in cosmological terms), both of which came close to the homogeneity scale but didn't exceed it. We published these in 2012. Then this year we published the new discovery of the Huge-LQG. It does exceed the predicted homogeneity scale and thus challenges the assumption of the cosmological principle.’

They are very excited by the wide interest their work has generated and still have more examples to analyse. He says, ‘they won't be so extreme as the Huge-LQG but I think they'll constitute further challenges to the Cosmological Principle.’