|
C.L.G. Ard An Rátha
A galaxy cluster, or a cluster of galaxies, is a structure that consists of anywhere from hundreds to thousands of galaxies that are bound together by gravity, with typical masses ranging from 1014 to 1015 solar masses. They are the second-largest known gravitationally bound structures in the universe after galaxy filaments and were believed to be the largest known structures in the universe until the 1980s, when superclusters were discovered. One of the key features of clusters is the intracluster medium (ICM). The ICM consists of heated gas between the galaxies and has a peak temperature between 2–15 keV that is dependent on the total mass of the cluster. Galaxy clusters should not be confused with ''galactic clusters'' (also known as open clusters), which are star clusters ''within'' galaxies, or with globular clusters, which typically orbit galaxies. Small aggregates of galaxies are referred to as galaxy groups rather than clusters of galaxies. The galaxy groups ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fornax Cluster
The Fornax Cluster is a cluster of galaxies lying at a distance of 19 megaparsecs (62 million light-years). It has an estimated mass of solar masses, making it the second richest galaxy cluster within 100 million light-years, after the considerably larger Virgo Cluster. It may be associated with the nearby Eridanus Group. It lies primarily in the constellation Fornax, with its southern boundaries partially crossing into the constellation of Eridanus, and covers an area of sky about 6° across or about 28 sq degrees. The Fornax Cluster is a particularly valuable source of information about the evolution of such clusters due to its relatively close proximity to the Sun. It also shows the gravitational effects of a merger of a galaxy subgroup with the main galaxy group, which in turn lends clues about the associated galactic superstructure. At the centre of the cluster lies NGC 1399. Other cluster members include NGC 1316 (the group's brightest galaxy), NGC 1365, NGC 1427A, N ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
X-ray
An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz ( to ) and energies in the range 145 eV to 124 keV. X-ray wavelengths are shorter than those of UV rays and typically longer than those of gamma rays. In many languages, X-radiation is referred to as Röntgen radiation, after the German scientist Wilhelm Conrad Röntgen, who discovered it on November 8, 1895. He named it ''X-radiation'' to signify an unknown type of radiation.Novelline, Robert (1997). ''Squire's Fundamentals of Radiology''. Harvard University Press. 5th edition. . Spellings of ''X-ray(s)'' in English include the variants ''x-ray(s)'', ''xray(s)'', and ''X ray(s)''. The most familiar use of X-rays is checking for fractures (broken bones), but X-rays are also used in other ways. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Galaxy Cluster IDCS J1426
A galaxy is a system of stars, stellar remnants, interstellar gas, dust, dark matter, bound together by gravity. The word is derived from the Greek ' (), literally 'milky', a reference to the Milky Way galaxy that contains the Solar System. Galaxies, averaging an estimated 100 million stars, range in size from dwarfs with less than a hundred million stars, to the largest galaxies known – supergiants with one hundred trillion stars, each orbiting its galaxy's center of mass. Most of the mass in a typical galaxy is in the form of dark matter, with only a few percent of that mass visible in the form of stars and nebulae. Supermassive black holes are a common feature at the centres of galaxies. Galaxies are categorized according to their visual morphology as elliptical, spiral, or irregular. Many are thought to have supermassive black holes at their centers. The Milky Way's central black hole, known as Sagittarius A*, has a mass four million times greater than the Sun. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shock Waves In Astrophysics
Shock waves are common in astrophysical environments. Because of the low ambient density, most astronomical shocks are collisionless. This means that the shocks are not formed by two-body Coulomb collisions, since the mean free path for these collisions is too large, often exceeding the size of the system. Such shocks were first theorised by De Hoffmann and Teller, who studied shock waves in magnetized fluids with infinite conductivity. The precise mechanism for energy dissipation and entropy generation at such shocks is still under investigation, but it is widely accepted that the general mechanism driving these shocks consists of wave particle interaction and plasma instabilities, that operate on the scale of plasma skin depth, which is typically much shorter than the mean free path. It is known that collisionless shocks are associated with extremely high energy particles, although it has not been definitively established if the high energy photons observed are emitted by p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chandra X-ray Observatory
The Chandra X-ray Observatory (CXO), previously known as the Advanced X-ray Astrophysics Facility (AXAF), is a Flagship-class space telescope launched aboard the during STS-93 by NASA on July 23, 1999. Chandra is sensitive to X-ray sources 100 times fainter than any previous X-ray telescope, enabled by the high angular resolution of its mirrors. Since the Earth's atmosphere absorbs the vast majority of X-rays, they are not detectable from Earth-based telescopes; therefore space-based telescopes are required to make these observations. Chandra is an Earth satellite in a 64-hour orbit, and its mission is ongoing . Chandra is one of the Great Observatories, along with the Hubble Space Telescope, Compton Gamma Ray Observatory (1991–2000), and the Spitzer Space Telescope (2003–2020). The telescope is named after the Nobel Prize-winning Indian-American astrophysicist Subrahmanyan Chandrasekhar. Its mission is similar to that of ESA's XMM-Newton spacecraft, also launched in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radio Relics
Radio Relics are diffuse synchrotron radio sources found in the peripheral regions of galaxy clusters. As in the case of radio halos, they do not have any obvious galaxy counterpart, but their shapes are much more elongated and irregular compared to those of radio halos. Their energy distribution is steep (much more energy at low radio frequency than at high radio frequency), with hints of a distribution of different ages for the emitting electrons across the whole dimension of the emitting region. Radio relics can be divided into two main groups: Cluster radio shocks or radio gischt are large elongated, often Mpc-sized, radio sources located in the periphery of merging clusters. They probably trace shock fronts in which particles are accelerated via the diffusive shock acceleration mechanism. Among them are double-relics with the two relics located on both sides of a cluster center. Their integrated radio spectrum usually follows a single power-law. Radio phoenices are relate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radio Halo
Radio halos are large-scale sources of diffuse radio emission found in the center of some, but not all, galaxy clusters.Feretti, L., and G. Swarup. "The Universe at Low Radio Frequencies." Proceedings of IAU Symposium. Vol. 199. 2002. There are two classes of radio halos: mini-halos and giant radio halos. The linear size of giant radio halos is about 700kpc-1Mpc, whereas mini-halos are typically less than 500kpc. Giant radio halos are more often observed in highly X-ray luminous cluster samples than less luminous X-ray clusters (\mathrm_X \leq 10^ \mathrm^) in complete samples. They have a very low surface brightness and do not have obvious galaxy counterparts (in contrast to radio galaxies which have AGN counterparts). However, their morphologies typically follow the distribution of gas in the intra-cluster medium. Mini-halos however, while similar to giant halos, are found at the center of cooling core clusters but around a radio galaxy. The cause of radio haloes is still deba ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SPT-CL J2106-5844
SPT-CLJ2106-5844 is a galaxy cluster located 7.5 billion light years from Earth. It was discovered by scientists from the South Pole Telescope Collaboration, using the South Pole Telescope The South Pole Telescope (SPT) is a diameter telescope located at the Amundsen–Scott South Pole Station, Antarctica. The telescope is designed for observations in the microwave, millimeter-wave, and submillimeter-wave regions of the electrom .... With a weight of about 1.27 × 1015 solar masses, it is the most massive distant object known, as of 2011. It is about 60% heavier than previously known object detected in 2008, SPT-CL J0546-5345. This galaxy cluster was found in the South Pole Telescope Sunyaev-Zel'dovich (SPT-SZ) survey. This survey was done using the Advanced Camera for Surveys and Wide Field Camera 3 on the Hubble Space Telescope. There have been many observations completed in x-ray and infrared imaging to discover new observations about this massive cluster. Like how the cen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SPT-CL J0546-5345
SPT-CL J0546-5345 is one of the most massive galaxy clusters ever found in the early universe. It is thought to be 7 billion light years away. It was discovered at the South Pole Telescope in 2008 by the Sunyaev-Zel'dovich-Effect. The cluster has a redshift of z=1.067. Follow-up studies using the Spitzer, Chandra Chandra ( sa, चन्द्र, Candra, shining' or 'moon), also known as Soma ( sa, सोम), is the Hindu god of the Moon, and is associated with the night, plants and vegetation. He is one of the Navagraha (nine planets of Hinduism) an ..., and optical telescopes allowed to identify cluster members and to measure the redshift. Using the velocity dispersion, the cluster mass has been estimated to 1015 solar masses. See also * SPT-CL J2106-5844 References Galaxy clusters Pictor (constellation) {{galaxy-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hubble's Law
Hubble's law, also known as the Hubble–Lemaître law, is the observation in physical cosmology that galaxies are moving away from Earth at speeds proportional to their distance. In other words, the farther they are, the faster they are moving away from Earth. The velocity of the galaxies has been determined by their redshift, a shift of the light they emit toward the red end of the visible spectrum. Hubble's law is considered the first observational basis for the expansion of the universe, and today it serves as one of the pieces of evidence most often cited in support of the Big Bang model. The motion of astronomical objects due solely to this expansion is known as the Hubble flow. It is described by the equation , with ''H''0 the constant of proportionality—the Hubble constant—between the "proper distance" ''D'' to a galaxy, which can change over time, unlike the comoving distance, and its speed of separation ''v'', i.e. the derivative of proper distance with respect ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Norma Cluster
The Norma Cluster (ACO 3627 or Abell 3627) is a rich cluster of galaxies located near the center of the Great Attractor; it is about distant. Although it is both nearby and bright, it is difficult to observe because it is located in the Zone of Avoidance, a region near the plane of the Milky Way. Consequently, the cluster is severely obscured by interstellar dust at optical wavelengths. Its mass is estimated to be on the order of 1015 solar masses. ESO 137-001, an example of a jellyfish galaxy, is located in Abell 3627. See also * List of galaxy groups and clusters * Coma Cluster * Eridanus Cluster * Fornax Cluster * Virgo Cluster * X-ray astronomy References External links ESO Press Photos 46a-j/99* NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeeding t ... Image of the Day, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
