A large quasar group (LQG) is a collection of

quasar A quasar is an extremely Luminosity, luminous active galactic nucleus (AGN). It is pronounced , and sometimes known as a quasi-stellar object, abbreviated QSO. This emission from a galaxy nucleus is powered by a supermassive black hole with a m ...

s (a form of

supermassive black hole A supermassive black hole (SMBH or sometimes SBH) is the largest type of black hole, with its mass being on the order of hundreds of thousands, or millions to billions of times the mass of the Sun (). Black holes are a class of astronomical obj ...

active galactic nuclei An active galactic nucleus (AGN) is a compact region at the center of a galaxy that has a much-higher-than-normal luminosity over at least some portion of the electromagnetic spectrum with characteristics indicating that the luminosity is not prod ...

) that form what are thought to constitute the largest astronomical structures in the

observable universe The observable universe is a ball-shaped region of the universe comprising all matter that can be observed from Earth or its space-based telescopes and exploratory probes at the present time, because the electromagnetic radiation from these obj ...

. LQGs are thought to be precursors to the sheets, walls and filaments of galaxies found in the relatively nearby universe.

Prominent LQGs

On January 11, 2013, the discovery of the

Huge-LQG The Huge Large Quasar Group, (Huge-LQG, also called U1.27) is a possible structure or pseudo-structure of 73 quasars, referred to as a large quasar group, that measures about 4 billion light-years across. At its discovery, it was identified as ...

was announced by the

University of Central Lancashire , mottoeng = "From the Earth to the Sun" , established = as Institution for the Diffusion of Useful Knowledgere-established 1992 (University status granted) , type = Public , chancellor ...

, as the largest known structure in the universe by that time. It is composed of 74

s and has a minimum diameter of 1.4 billion

light-year A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...

s, but over 4 billion light-years at its widest point. According to researcher and author, Roger Clowes, the existence of structures with the size of LQGs was believed theoretically impossible. Cosmological structures had been believed to have a size limit of approximately 1.2 billion light-years.

List of LQGs

Prominent LQGs

List of LQGs

See also

References

Further reading