| Part of a series on |
| Physical cosmology |
|---|
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. [1]
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. [2] 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. [3] [4]
 | This section may be too technical for most readers to understand.(July 2023) |
Redshift, denoted as "z," is a fundamental concept in astrophysics used to measure the spectral line shift in light emitted by celestial objects like quasars due to their motion away from Earth. In the table below, higher redshift values directly correspond to greater cosmic distances.
| LQG | Date | Mean Distance | Dimension | # of quasars | Notes |
|---|---|---|---|---|---|
| Webster LQG (LQG 1) | 1982 | z=0.37 | 100 Mpc | 5 | First LQG discovered. At the time of its discovery, it was the largest structure known. [1] [4] [5] |
| Crampton–Cowley–Hartwick LQG (LQG 2, CCH LQG, Komberg-Kravtsov-Lukash LQG 10) | 1987 | z=1.11 | 60 Mpc | 28 | Second LQG discovered [1] [4] [6] |
| Clowes–Campusano LQG (U1.28, CCLQG, LQG 3) | 1991 | z=1.28 |
| 34 | Third LQG discovered [4] [7] |
| U1.90 | 1995 | z=1.9 | 120 Mpc/h | 10 | Discovered by Graham, Clowes, Campusano. [1] [6] [8] |
| 7Sf Group (U0.19) | 1995 | z=0.19 | 60 Mpc/h | 7 | Discovered by Graham, Clowes, Campusano; this is a grouping of 7 Seyfert galaxies. [1] [6] [8] |
| Komberg–Kravtsov–Lukash LQG 1 | 1996 | z=0.6 | R=96 Mpc/h | 12 | Discovered by Komberg, Kravtsov, Lukash. [1] [6] |
| Komberg–Kravtsov–Lukash LQG 2 | 1996 | z=0.6 | R=111 Mpc/h | 12 | Discovered by Komberg, Kravtsov, Lukash. [1] [6] |
| Komberg–Kravtsov–Lukash LQG 3 | 1996 | z=1.3 | R=123 Mpc/h | 14 | Discovered by Komberg, Kravtsov, Lukash. [1] [6] |
| Komberg–Kravtsov–Lukash LQG 4 | 1996 | z=1.9 | R=104 Mpc/h | 14 | Discovered by Komberg, Kravtsov, Lukash. [1] [6] |
| Komberg–Kravtsov–Lukash LQG 5 | 1996 | z=1.7 | R=146 Mpc/h | 13 | Discovered by Komberg, Kravtsov, Lukash. [1] [6] |
| Komberg–Kravtsov–Lukash LQG 6 | 1996 | z=1.5 | R=94 Mpc/h | 10 | Discovered by Komberg, Kravtsov, Lukash. [1] [6] |
| Komberg–Kravtsov–Lukash LQG 7 | 1996 | z=1.9 | R=92 Mpc/h | 10 | Discovered by Komberg, Kravtsov, Lukash. [1] [6] |
| Komberg–Kravtsov–Lukash LQG 8 | 1996 | z=2.1 | R=104 Mpc/h | 12 | Discovered by Komberg, Kravtsov, Lukash. [1] [6] |
| Komberg–Kravtsov–Lukash LQG 9 | 1996 | z=1.9 | R=66 Mpc/h | 18 | Discovered by Komberg, Kravtsov, Lukash. [1] [6] |
| Komberg–Kravtsov–Lukash LQG 11 | 1996 | z=0.7 | R=157 Mpc/h | 11 | Discovered by Komberg, Kravtsov, Lukash. [1] [6] |
| Komberg–Kravtsov–Lukash LQG 12 | 1996 | z=1.2 | R=155 Mpc/h | 14 | Discovered by Komberg, Kravtsov, Lukash. [1] [6] |
| Newman LQG (U1.54) | 1998 | z=1.54 | 150 Mpc/h | 21 | Discovered by P.R. Newman [9] 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., [1] [7] |
| Tesch–Engels LQG | 2000 | z=0.27 | 140 Mpc/h | 7 | The first X-ray selected LQG. [1] |
| U1.11 | 2011 | z=1.11 |
| 38 | [4] [7] |
| Huge-LQG (U1.27) | 2013 | z=1.27 |
| 73 | The largest structure known in the observable universe [4] [10] until it was eclipsed by the Hercules–Corona Borealis Great Wall found one year later. [11] [12] [13] |
In physical cosmology, the Copernican principle states that humans, on the Earth or in the Solar System, are not privileged observers of the universe, that observations from the Earth are representative of observations from the average position in the universe. Named for Copernican heliocentrism, it is a working assumption that arises from a modified cosmological extension of Copernicus' argument of a moving Earth.
A quasar is an extremely luminous active galactic nucleus (AGN). It is sometimes known as a quasi-stellar object, abbreviated QSO. The emission from an AGN is powered by a supermassive black hole with a mass ranging from millions to tens of billions of solar masses, surrounded by a gaseous accretion disc. Gas in the disc falling towards the black hole heats up and releases energy in the form of electromagnetic radiation. The radiant energy of quasars is enormous; the most powerful quasars have luminosities thousands of times greater than that of a galaxy such as the Milky Way. Quasars are usually categorized as a subclass of the more general category of AGN. The redshifts of quasars are of cosmological origin.
In modern physical cosmology, the cosmological principle is the notion that the spatial distribution of matter in the universe is uniformly isotropic and homogeneous when viewed on a large enough scale, since the forces are expected to act equally throughout the universe on a large scale, and should, therefore, produce no observable inequalities in the large-scale structuring over the course of evolution of the matter field that was initially laid down by the Big Bang.
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; the electromagnetic radiation from these objects has had time to reach the Solar System and Earth since the beginning of the cosmological expansion. Initially, it was estimated that there may be 2 trillion galaxies in the observable universe. That number was reduced in 2021 to only several hundred billion based on data from New Horizons. Assuming the universe is isotropic, the distance to the edge of the observable universe is roughly the same in every direction. That is, the observable universe is a spherical region centered on the observer. Every location in the universe has its own observable universe, which may or may not overlap with the one centered on Earth.
In the fields of Big Bang theory and cosmology, reionization is the process that caused electrically neutral atoms in the universe to reionize after the lapse of the "dark ages".
The Lambda-CDM, Lambda cold dark matter, or ΛCDM model is a mathematical model of the Big Bang theory with three major components:
Redshift quantization, also referred to as redshift periodicity, redshift discretization, preferred redshifts and redshift-magnitude bands, is the hypothesis that the redshifts of cosmologically distant objects tend to cluster around multiples of some particular value.
The Sloan Great Wall (SGW) is a cosmic structure formed by a giant wall of galaxies. Its discovery was announced from Princeton University on October 20, 2003, by J. Richard Gott III, Mario Jurić, and their colleagues, based on data from the Sloan Digital Sky Survey.
Galaxy mergers can occur when two galaxies collide. They are the most violent type of galaxy interaction. The gravitational interactions between galaxies and the friction between the gas and dust have major effects on the galaxies involved. The exact effects of such mergers depend on a wide variety of parameters such as collision angles, speeds, and relative size/composition, and are currently an extremely active area of research. Galaxy mergers are important because the merger rate is a fundamental measurement of galaxy evolution. The merger rate also provides astronomers with clues about how galaxies bulked up over time.
In cosmology, galaxy filaments are the largest known structures in the universe, consisting of walls of galactic superclusters. These massive, thread-like formations can commonly reach 50/h to 80/h Megaparsecs — with the largest found to date being the Hercules-Corona Borealis Great Wall at around 3 gigaparsecs (9.8 Gly) in length — and form the boundaries between voids. Due to the accelerating expansion of the universe, the individual clusters of gravitationally bound galaxies that make up galaxy filaments are moving away from each other at an accelerated rate; in the far future they will dissolve.
In cosmology, the steady-state model or steady state theory is an alternative to the Big Bang theory. In the steady-state model, the density of matter in the expanding universe remains unchanged due to a continuous creation of matter, thus adhering to the perfect cosmological principle, a principle that says that the observable universe is always the same at any time and any place.
The Huge Large Quasar Group, 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 the largest and the most massive known structure in the observable universe, though it has been superseded by the Hercules–Corona Borealis Great Wall at 10 billion light-years. There are also issues about its structure.
The Hercules–Corona Borealis Great Wall (HCB) or simply the Great Wall is a galaxy filament that is the largest known structure in the observable universe, measuring approximately 10 billion light-years in length. This massive superstructure is a region of the sky seen in the data set mapping of gamma-ray bursts (GRBs) that has been found to have a concentration of similarly distanced GRBs that is unusually higher than the expected average distribution. It was discovered in early November 2013 by a team of American and Hungarian astronomers led by István Horváth, Jon Hakkila and Zsolt Bagoly while analyzing data from the Swift Gamma-Ray Burst Mission, together with other data from ground-based telescopes. It is the largest known formation in the universe, exceeding the size of the prior Huge-LQG by about a factor of two.
The Clowes–Campusano LQG is a large quasar group, consisting of 34 quasars and measuring about 2 billion light-years across. It is one of the largest known superstructures in the observable universe. It is located near the larger Huge-LQG. It was discovered by the astronomers Roger Clowes and Luis Campusano in 1991.
U1.11 is a large quasar group located in the constellations of Leo and Virgo. It is one of the largest LQG's known, with the estimated maximum diameter of 780 Mpc and contains 38 quasars. It was discovered in 2011 during the course of the Sloan Digital Sky Survey. Until the discovery of the Huge-LQG in November 2012, it was the largest known structure in the universe, beating Clowes–Campusano LQG's 20-year record as largest known structure at the time of its discovery.
Direct collapse black holes (DCBHs) are high-mass black hole seeds, putatively formed within the redshift range z=15–30, when the Universe was about 100–250 million years old. Unlike seeds formed from the first population of stars (also known as Population III stars), direct collapse black hole seeds are formed by a direct, general relativistic instability. They are very massive, with a typical mass at formation of ~105 M☉. This category of black hole seeds was originally proposed theoretically to alleviate the challenge in building supermassive black holes already at redshift z~7, as numerous observations to date have confirmed.
