A large quasar group (LQG) is a collection of quasars (a form of supermassive black hole active galactic nuclei) that form what are thought to constitute the largest astronomical structures in the observable universe. 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 was announced by the University of Central Lancashire, as the largest known structure in the universe by that time. It is composed of 74 quasars and has a minimum diameter of 1.4 billion light-years, 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.
Other scientists have expressed doubt whether these structures really exist.
List of LQGs
Redshift, represented by "z," is a fundamental concept in astrophysics. It measures how much the light from celestial objects shift as they move away from Earth. A higher redshift value means the object is farther away in the universe. + Large Quasar Groups LQG Date Mean Distance Dimension # of quasars Notes Webster LQG (LQG 1) 1982 z=0.37 Mpc 5 First LQG discovered. At the time of its discovery, it was the largest structure known.R.G.Clowes; "Large Quasar Groups - A Short Review"; 'The New Era of Wide Field Astronomy', ASP Conference Series, Vol. 232.; 2001; Astronomical Society of the Pacific; ; Crampton–Cowley–Hartwick LQG (LQG 2, CCH LQG, Komberg-Kravtsov-Lukash LQG 10) 1987 z=1.11 Mpc 28 Second LQG discovered Clowes–Campusano LQG (U1.28, CCLQG, LQG 3) 1991 z=1.28 34 Third LQG discovered U1.90 1995 z=1.9 Mpc/h 10 Discovered by Graham, Clowes, Campusano. 7Sf Group (U0.19) 1995 z=0.19 Mpc/h 7 Discovered by Graham, Clowes, Campusano; this is a grouping of 7 Seyfert galaxies. Komberg–Kravtsov–Lukash LQG 1 1996 z=0.6 R=96 Mpc/h 12 Discovered by Komberg, Kravtsov, Lukash. Komberg–Kravtsov–Lukash LQG 2 1996 z=0.6 R=111 Mpc/h 12 Discovered by Komberg, Kravtsov, Lukash. Komberg–Kravtsov–Lukash LQG 3 1996 z=1.3 R=123 Mpc/h 14 Discovered by Komberg, Kravtsov, Lukash. Komberg–Kravtsov–Lukash LQG 4 1996 z=1.9 R=104 Mpc/h 14 Discovered by Komberg, Kravtsov, Lukash. Komberg–Kravtsov–Lukash LQG 5 1996 z=1.7 R=146 Mpc/h 13 Discovered by Komberg, Kravtsov, Lukash. Komberg–Kravtsov–Lukash LQG 6 1996 z=1.5 R=94 Mpc/h 10 Discovered by Komberg, Kravtsov, Lukash. Komberg–Kravtsov–Lukash LQG 7 1996 z=1.9 R=92 Mpc/h 10 Discovered by Komberg, Kravtsov, Lukash. Komberg–Kravtsov–Lukash LQG 8 1996 z=2.1 R=104 Mpc/h 12 Discovered by Komberg, Kravtsov, Lukash. Komberg–Kravtsov–Lukash LQG 9 1996 z=1.9 R=66 Mpc/h 18 Discovered by Komberg, Kravtsov, Lukash. Komberg–Kravtsov–Lukash LQG 11 1996 z=0.7 R=157 Mpc/h 11 Discovered by Komberg, Kravtsov, Lukash. Komberg–Kravtsov–Lukash LQG 12 1996 z=1.2 R=155 Mpc/h 14 Discovered by Komberg, Kravtsov, Lukash. Newman LQG (U1.54) 1998 z=1.54 Mpc/h 21 Discovered by P.R. Newman et al. This structure is parallel to the CCLQG, with its discovery, suggesting that the cellular structure of sheets and voids already existed in this era, as found in later void bubbles and walls of galaxies., Tesch–Engels LQG 2000 z=0.271 Mpc/h 7 The first X-ray selected LQG. U1.11 2011 z=1.11 38 Huge-LQG (U1.27) 2013 z=1.27 73 The largest structure known in the observable universeScienceDaily, "Biggest Structure in Universe: Large Quasar Group Is 4 Billion Light Years Across", Royal Astronomical Society, 11 January 2013 (accessed 13 January 2013) until it was eclipsed by the Hercules–Corona Borealis Great Wall found one year later.
See also List of largest cosmic structures Large-scale structure of the cosmos
References
Further reading R. G. Clowes; "Large Quasar Groups - A Short Review"; 'The New Era of Wide Field Astronomy', ASP Conference Series, Vol. 232.; 2001; Astronomical Society of the Pacific; ;