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.
In the standard model of the evolution of the universe, galactic filaments form along and follow web-like strings of dark matter. It is thought that this dark matter dictates the structure of the Universe on the grandest of scales. Dark matter gravitationally attracts baryonic matter, and it is this "normal" matter that astronomers see forming long, thin walls of super-galactic clusters.
Discovery of structures larger than superclusters began in the late-1980s. In 1987, astronomer R. Brent Tully of the University of Hawaii's Institute of Astronomy identified what he called the Pisces–Cetus Supercluster Complex. In 1989, the CfA2 Great Wall was discovered, followed by the Sloan Great Wall in 2003. On January 11, 2013, researchers led by Roger Clowes of the University of Central Lancashire announced the discovery of a large quasar group, the Huge-LQG, which dwarfs previously discovered galaxy filaments in size. In November 2013, using gamma-ray bursts as reference points, astronomers discovered the Hercules–Corona Borealis Great Wall, an extremely huge filament measuring more than 10 billion light-years across.
Filament subtype of filaments have roughly similar major and minor axes in cross-section, along the lengthwise axis.
|Coma Filament||The Coma Supercluster lies within the Coma Filament. It forms part of the CfA2 Great Wall.|
|Perseus–Pegasus Filament||1985||Connected to the Pisces–Cetus Supercluster, with the Perseus–Pisces Supercluster being a member of the filament.|
|Ursa Major Filament||Connected to the CfA Homunculus, a portion of the filament forms a portion of the "leg" of the Homunculus.|
|Lynx–Ursa Major Filament (LUM Filament)||1999||from 2000 km/s to 8000 km/s in redshift space||Connected to and separate from the Lynx–Ursa Major Supercluster.|
|z=2.38 filament around protocluster ClG J2143-4423||2004||z=2.38||110Mpc||A filament the length of the Great Wall was discovered in 2004. As of 2008, it was still the largest structure beyond redshift 2.|
The galaxy wall subtype of filaments have a significantly greater major axis than minor axis in cross-section, along the lengthwise axis.
|CfA2 Great Wall (Coma Wall, Great Wall, Northern Great Wall, Great Northern Wall, CfA Great Wall)||1989||z=0.03058||251Mpc long
||This was the first super-large large-scale structure or pseudo-structure in the universe to be discovered. The CfA Homunculus lies at the heart of the Great Wall, and the Coma Supercluster forms most of the homunculus structure. The Coma Cluster lies at the core.|
|Sloan Great Wall (SDSS Great Wall)||2003||z=0.07804||433Mpc long||This was the largest known galaxy filament to be discovered, until it was eclipsed by the Hercules–Corona Borealis Great Wall found ten years later.|
|Sculptor Wall (Southern Great Wall, Great Southern Wall, Southern Wall)||8000 km/s long
5000 km/s wide
1000 km/s deep
(in redshift space dimensions)
|The Sculptor Wall is "parallel" to the Fornax Wall and "perpendicular" to the Grus Wall.|
|Grus Wall||The Grus Wall is "perpendicular" to the Fornax and Sculptor Walls.|
|Fornax Wall||The Fornax Cluster is part of this wall. The wall is "parallel" to the Sculptor Wall and "perpendicular" to the Grus Wall.|
|Hercules–Corona Borealis Great Wall||2013||z≈2||3 Gpc long,
150 000 km/s deep
(in redshift space)
|The largest known structure in the universe. This is also the first time since 1991 that a galaxy filament/great wall held the record as the largest known structure in the universe.|
||It was the largest known structure in the universe from 1991 to 2011, until U1.11's discovery.|
||Was the largest known structure in the universe for a few months, until Huge-LQG's discovery.|
||It was the largest structure known in the universe, until the discovery of the Hercules–Corona Borealis Great Wall found one year later.|
|Pisces–Cetus Supercluster Complex||1987||1 billion ly wide,
150 million ly deep
|Contains Virgo Supercluster and Local Group|
The Great Wall (also called Coma Wall), sometimes specifically referred to as the CfA2 Great Wall, is an immense galaxy filament. It is one of the largest known superstructures in the observable universe.
This structure was discovered c. 1989 by a team of American astronomers led by Margaret J. Geller and John Huchra while analyzing data gathered by the second CfA Redshift Survey of the Harvard-Smithsonian Center for Astrophysics (CfA).Coma Filament
Coma Filament is a galaxy filament. The filament contains the Coma Supercluster of galaxies and forms a part of the CfA2 Great Wall.Cygnus (constellation)
Cygnus is a northern constellation lying on the plane of the Milky Way, deriving its name from the Latinized Greek word for swan. Cygnus is one of the most recognizable constellations of the northern summer and autumn, and it features a prominent asterism known as the Northern Cross (in contrast to the Southern Cross). Cygnus was among the 48 constellations listed by the 2nd century astronomer Ptolemy, and it remains one of the 88 modern constellations.
Cygnus contains Deneb (ذنب, translit. ḏanab, tail) -which is one of the brightest stars in the night sky and is the most distant first-magnitude star- as its "tail star" and one corner of the Summer Triangle. It also has some notable X-ray sources and the giant stellar association of Cygnus OB2. Cygnus is also known as the Northern Cross. One of the stars of this association, NML Cygni, is one of the largest stars currently known. The constellation is also home to Cygnus X-1, a distant X-ray binary containing a supergiant and unseen massive companion that was the first object widely held to be a black hole. Many star systems in Cygnus have known planets as a result of the Kepler Mission observing one patch of the sky, an area around Cygnus. In addition, most of the eastern part of Cygnus is dominated by the Hercules–Corona Borealis Great Wall, a giant galaxy filament that is the largest known structure in the observable universe, covering most of the northern sky.Fornax Wall
The Fornax Wall is a superstructure known as a galaxy filament or galaxy wall. It is a long filament of galaxies with a major axis longer than its minor one. The filament contains not only Dorado Group but also the Fornax cluster of galaxies, which lies at the same distance. It is "parallel" to the Sculptor Wall and "perpendicular" to the Grus Wall.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.Lynx–Ursa Major Filament
Lynx–Ursa Major Filament (LUM Filament) is a galaxy filament.The filament is connected to and separate from the Lynx–Ursa Major Supercluster.NGC 5965
NGC 5965 is a spiral galaxy located in the constellation Draco. It is located at a distance of circa 150 million light years from Earth, which, given its apparent dimensions, means that NGC 5965 is about 260,000 light years across. It was discovered by William Herschel οn May 5, 1788. Two supernovae have been observed in NGC 5965, SN 2001 cm (type II, mag 17.5) and SN 2018cyg (type II, mag 17.0).NGC 5965 is seen nearly edge-on, with an inclination of 80 degrees. Dust is seen across the galactic disk, while there is also a red dust lane at the nucleus. The bulge is X-shaped, that suggests that the galaxy is actually barred. NGC 5965 along with another edge-on galaxy, NGC 5746, were the galaxies used to confirm that peanut shaped bulge are associated with the presence of a bar, by spectographically observing the disturbance caused at the velocity distributions of the galaxies.
The galaxy features some level of disk disturbance, like a warp, as the outer part of the disk along with a ring-like dust lane appear to be on a different plane from the bulge, but it could also be a projection effect. When observed in K band, the galaxy features a stellar ring.NGC 5965 lies in a galaxy filament which also includes NGC 5987 and its loose group, which includes NGC 5981, NGC 5982, NGC 5985, three galaxies known as the Sampler.Perseus–Pegasus Filament
Perseus–Pegasus Filament is a galaxy filament containing the Perseus-Pisces Supercluster and stretching for roughly a billion light years (or over 300/h Mpc). Currently, it is considered to be one of the largest known structures in the universe. This filament is adjacent to the Pisces–Cetus Supercluster Complex.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.Pisces–Cetus Supercluster Complex
The Pisces–Cetus Supercluster Complex is a galaxy filament. It includes the Virgo Supercluster which in turn contains the Local Group, the galaxy cluster that includes the Milky Way.
This filament is adjacent to the Perseus–Pegasus Filament.
However, a 2014 study indicates that the Virgo Supercluster is only a lobe of a greater supercluster, Laniakea.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.Saraswati Supercluster
The Saraswati Supercluster is a massive galaxy supercluster about 1.2 gigaparsecs (4,000 million light years) away within the Stripe 82 region of SDSS, in the direction of the constellation Pisces. It is one of the largest structures found in the universe, with a major axis in diameter of about 200 Mpc (652 million light years). It consists of at least 43 galaxy clusters, and has the mass of 2 × 1016 M☉, forming a galaxy filament.Sloan Great Wall
The Sloan Great Wall (SGW) is a cosmic structure formed by a giant wall of galaxies (a galaxy filament). 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.Somnath Bharadwaj
Somnath Bharadwaj (born 28 October 1964) is an Indian theoretical physicist who works on Theoretical Astrophysics and Cosmology.
Bharadwaj was born in India, studied at the Indian Institute of Technology in Kharagpur, and later received his Ph.D. from the Indian Institute of Science. After having worked at the Harish-Chandra Research Institute, he is now a professor at IIT Kharagpur. He has made significant contributions to the dynamics of large-scale structure formation.
In 2003, he was selected to be one of the professors from IIT whose class room lectures would be broadcast in the Eklavya Technology Channel.Bharadwaj was an invited speakers on Galaxy Formation at the prestigious Indo-US Frontier of Science symposium which was organized by the U.S. National Academy of Sciences in 2005.He is currently in the Editorial Board of the Journal of Astrophysics & Astronomy published by the Indian Academy of Sciences.Supercluster
A supercluster is a large group of smaller galaxy clusters or galaxy groups; it is among the largest-known structures of the cosmos. The Milky Way is part of the Local Group galaxy group (which contains more than 54 galaxies), which in turn is part of the Laniakea Supercluster. This supercluster spans over 500 million light-years, while the Local Group spans over 10 million light-years. The number of superclusters in the observable universe is estimated to be 10 million.Ursa Major Filament
Ursa Major Filament is a galaxy filament. The filament is connected to the CfA Homunculus, a portion of the filament forms a portion of the "leg" of the Homunculus.Virgo Supercluster
The Virgo Supercluster (Virgo SC) or the Local Supercluster (LSC or LS) is a mass concentration of galaxies containing the Virgo Cluster and Local Group, which in turn contains the Milky Way and Andromeda galaxies. At least 100 galaxy groups and clusters are located within its diameter of 33 megaparsecs (110 million light-years). The Virgo SC is one of about 10 million superclusters in the observable universe and is in the Pisces–Cetus Supercluster Complex, a galaxy filament.
A 2014 study indicates that the Virgo Supercluster is only a lobe of an even greater supercluster, Laniakea, a larger, competing referent of Local Supercluster centered on the Great Attractor.