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 known universe. LQGs are thought to be precursors to the sheets, walls and filaments of galaxies found in the relatively nearby universe.
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 comprises 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.
|LQG||Date||Mean Distance||Dimension||# of quasars||Notes|
|1982||z=0.37||100 Mpc||5||First LQG discovered. At the time of its discovery, it was the largest structure known.|
(LQG 2, CCH LQG, Komberg-Kravtsov-Lukash LQG 10)
|1987||z=1.11||60 Mpc||28||Second LQG discovered |
(U1.28, CCLQG, LQG 3)
||34||Third LQG discovered |
|1995||z=1.9||120 Mpc/h||10||Discovered by Graham, Clowes, Campusano.|
|1995||z=0.19||60 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.|
|1998||z=1.54||150 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=0.27||140 Mpc/h||7||The first X-ray selected LQG.|
||73||The largest structure known in the observable universe until it was eclipsed by the Hercules–Corona Borealis Great Wall found one year later.|
The Big Crunch is one of the theoretical scenarios for the ultimate fate of the universe, in which the metric expansion of space eventually reverses and the universe recollapses, ultimately causing the cosmic scale factor to reach zero or causing a reformation of the universe starting with another Big Bang.
Some experimental evidence casts doubt on this theory and suggests that the expansion of the universe is accelerating, rather than being slowed down by gravity. However, more recent research has called this conclusion into question.Black Hole Initiative
The Black Hole Initiative (BHI) is an interdisciplinary program at Harvard University that includes the fields of Astronomy, Physics and Philosophy, and is claimed to be the first center in the world to focus on the study of black holes. Notable principal participants include: Sheperd Doeleman, Peter Galison, Avi Loeb, Ramesh Narayan, Andrew Strominger and Shing-Tung Yau. The BHI Inauguration was held on 18 April 2016 and was attended by Stephen Hawking; related workshop events were held on 19 April 2016. Robert Dijkgraaf created the mural for the BHI Inauguration.
If determinism — the predictability of the universe — breaks down in black holes, it could break down in other situations. Even worse, if determinism breaks down, we can’t be sure of our past history either. The history books and our memories could just be illusions. It is the past that tells us who we are. Without it, we lose our identity.Clowes–Campusano LQG
The Clowes–Campusano LQG (CCLQG; also called LQG 3 and U1.28) is a large quasar group, consisting of 34 quasars and measures 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.Cosmic background radiation
Cosmic background radiation is electromagnetic radiation from the Big Bang. The origin of this radiation depends on the region of the spectrum that is observed. One component is the cosmic microwave background. This component is redshifted photons that have freely streamed from an epoch when the Universe became transparent for the first time to radiation. Its discovery and detailed observations of its properties are considered one of the major confirmations of the Big Bang. The discovery (by chance in 1965) of the cosmic background radiation suggests that the early universe was dominated by a radiation field, a field of extremely high temperature and pressure.The Sunyaev–Zel'dovich effect shows the phenomena of radiant cosmic background radiation interacting with "electron" clouds distorting the spectrum of the radiation.
There is also background radiation in the infrared, x-rays, etc., with different causes, and they can sometimes be resolved into an individual source. See cosmic infrared background and X-ray background. See also cosmic neutrino background and extragalactic background light.Cosmological principle
In modern physical cosmology, the cosmological principle is the notion that the spatial distribution of matter in the universe is homogeneous and isotropic when viewed on a large enough scale, since the forces are expected to act uniformly throughout the universe, and should, therefore, produce no observable irregularities in the large-scale structuring over the course of evolution of the matter field that was initially laid down by the Big Bang.Galaxy filament
In physical cosmology, galaxy filaments (subtypes: supercluster complexes, galaxy walls, and galaxy sheets) are the largest known structures in the universe. They are massive, thread-like formations, with a typical length of 50 to 80 megaparsecs h−1 (163 to 261 million light-years) that form the boundaries between large voids in the universe. Filaments consist of gravitationally bound galaxies. Parts wherein many galaxies are very close to one another (in cosmic terms) are called superclusters.Grand unification epoch
In physical cosmology, assuming that nature is described by a Grand Unified Theory, the grand unification epoch was the period in the evolution of the early universe following the Planck epoch, starting at about 10−43 seconds after the Big Bang, in which the temperature of the universe was comparable to the characteristic temperatures of grand unified theories. If the grand unification energy is taken to be 1015 GeV, this corresponds to temperatures higher than 1027 K. During this period, three of the four fundamental interactions—electromagnetism, the strong interaction, and the weak interaction—were unified as the electronuclear force. Gravity had separated from the electronuclear force at the end of the Planck era. During the grand unification epoch, physical characteristics such as mass, charge, flavour and colour charge were meaningless.
The grand unification epoch ended at approximately 10−36 seconds after the Big Bang. At this point several key events took place. The strong force separated from the other fundamental forces.
It is possible that some part of this decay process violated the conservation of baryon number and gave rise to a small excess of matter over antimatter (see baryogenesis). This phase transition is also thought to have triggered the process of cosmic inflation that dominated the development of the universe during the following inflationary epoch.Graphical timeline of the Big Bang
This timeline of the Big Bang shows a sequence of events as currently theorized by scientists.
It is a logarithmic scale that shows second instead of second. For example, one microsecond is . To convert −30 read on the scale to second calculate second = one millisecond. On a logarithmic time scale a step lasts ten times longer than the previous step.Hadron epoch
In physical cosmology, the hadron epoch was the period in the evolution of the early universe during which the mass of the universe was dominated by hadrons. It started approximately 10−6 seconds after the Big Bang, when the temperature of the universe had fallen sufficiently to allow the quarks from the preceding quark epoch to bind together into hadrons. Initially the temperature was high enough to allow the formation of hadron/anti-hadron pairs, which kept matter and anti-matter in thermal equilibrium. However, as the temperature of the universe continued to fall, hadron/anti-hadron pairs were no longer produced. Most of the hadrons and anti-hadrons were then eliminated in annihilation reactions, leaving a small residue of hadrons. The elimination of anti-hadrons was completed by one second after the Big Bang, when the following lepton epoch began.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 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 (see Dispute section below).LQG
LQG as an acronym may refer to:
Loop quantum gravity, a proposed quantum theory of spacetime
Liouville quantum gravity, a theory of gravity on two-dimensional surfaces
Linear-quadratic-Gaussian control, most fundamental optimal control problem
Large quasar group, a massive collection of black holes and the largest known object in the universeLepton epoch
In physical cosmology, the lepton epoch was the period in the evolution of the early universe in which the leptons dominated the mass of the universe. It started roughly 1 second after the Big Bang, after the majority of hadrons and anti-hadrons annihilated each other at the end of the hadron epoch. During the lepton epoch the temperature of the universe was still high enough to create lepton/anti-lepton pairs, so leptons and anti-leptons were in thermal equilibrium. Approximately 10 seconds after the Big Bang the temperature of the universe had fallen to the point where lepton/anti-lepton pairs were no longer created. Most leptons and anti-leptons were then eliminated in annihilation reactions, leaving a small residue of leptons. The mass of the universe was then dominated by photons as it entered the following photon epoch.Marc Aaronson
Marc Aaronson (24 August 1950 – 30 April 1987) was an American astronomer.Matter power spectrum
The matter power spectrum describes the density contrast of the universe (the difference between the local density and the mean density) as a function of scale. It is the Fourier transform of the matter correlation function. On large scales, gravity competes with cosmic expansion, and structures grow according to linear theory. In this regime, the density contrast field is Gaussian, Fourier modes evolve independently, and the power spectrum is sufficient to completely describe the density field. On small scales, gravitational collapse is non-linear, and can only be computed accurately using N-body simulations. Higher-order statistics are necessary to describe the full field at small scales.Observable universe
The observable universe is a spherical 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 electromagnetic radiation from these objects has had time to reach the Solar System and Earth since the beginning of the cosmological expansion. There are at least 2 trillion galaxies in the observable universe. 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 has a spherical volume (a ball) 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.
The word observable in this sense does not refer to the capability of modern technology to detect light or other information from an object, or whether there is anything to be detected. It refers to the physical limit created by the speed of light itself. Because no signals can travel faster than light, any object farther away from us than light could travel in the age of the Universe (estimated as of 2015 around 13.799±0.021 billion years) simply cannot be detected, as the signals could not have reached us yet. Sometimes astrophysicists distinguish between the visible universe, which includes only signals emitted since recombination—and the observable universe, which includes signals since the beginning of the cosmological expansion (the Big Bang in traditional physical cosmology, the end of the inflationary epoch in modern cosmology).
According to calculations, the current comoving distance—proper distance, which takes into account that the universe has expanded since the light was emitted—to particles from which the cosmic microwave background radiation (CMBR) was emitted, which represent the radius of the visible universe, is about 14.0 billion parsecs (about 45.7 billion light-years), while the comoving distance to the edge of the observable universe is about 14.3 billion parsecs (about 46.6 billion light-years), about 2% larger. The radius of the observable universe is therefore estimated to be about 46.5 billion light-years and its diameter about 28.5 gigaparsecs (93 billion light-years, 8.8×1023 kilometres or 5.5×1023 miles). The total mass of ordinary matter in the universe can be calculated using the critical density and the diameter of the observable universe to be about 1.5 × 1053 kg. In November 2018, astronomers reported that the extragalactic background light (EBL) amounted to 4 × 1084 photons.Since the expansion of the universe is known to accelerate and will become exponential in the future, the light emitted from all distant objects, past some time dependent on their current redshift, will never reach the Earth. In the future all currently observable objects will slowly freeze in time while emitting progressively redder and fainter light. For instance, objects with the current redshift z from 5 to 10 will remain observable for no more than 4–6 billion years. In addition, light emitted by objects currently situated beyond a certain comoving distance (currently about 19 billion parsecs) will never reach Earth.Photon epoch
In physical cosmology, the photon epoch was the period in the evolution of the early universe in which photons dominated the energy of the universe. The photon epoch started after most leptons and anti-leptons were annihilated at the end of the lepton epoch, about 10 seconds after the Big Bang. Atomic nuclei were created in the process of nucleosynthesis which occurred during the first few minutes of the photon epoch. For the remainder of the photon epoch, the universe contained a hot dense plasma of nuclei, electrons and photons. 370,000 years after the Big Bang the temperature of the universe fell to the point where nuclei could combine with electrons to create neutral atoms. As a result, photons no longer interacted frequently with matter, the universe became transparent and the cosmic microwave background radiation was created and then structure formation took place.Quark epoch
In physical cosmology the Quark epoch was the period in the evolution of the early universe when the fundamental interactions of gravitation, electromagnetism, the strong interaction and the weak interaction had taken their present forms, but the temperature of the universe was still too high to allow quarks to bind together to form hadrons. The quark epoch began approximately 10−12 seconds after the Big Bang, when the preceding electroweak epoch ended as the electroweak interaction separated into the weak interaction and electromagnetism. During the quark epoch the universe was filled with a dense, hot quark–gluon plasma, containing quarks, leptons and their antiparticles. Collisions between particles were too energetic to allow quarks to combine into mesons or baryons. The quark epoch ended when the universe was about 10−6 seconds old, when the average energy of particle interactions had fallen below the binding energy of hadrons. The following period, when quarks became confined within hadrons, is known as the hadron epoch.Religious interpretations of the Big Bang theory
Since the emergence of the Big Bang theory as the dominant physical cosmological paradigm, there have been a variety of reactions by religious groups regarding its implications for religious cosmologies. Some accept the scientific evidence at face value, some seek to harmonize the Big Bang with their religious tenets, and some reject or ignore the evidence for the Big Bang theory.U1.11
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 (2.2 billion light-years) 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.