A galaxy cluster, or 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 1014–1015 solar masses. They are the largest known gravitationally bound structures in the universe 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; the ICM consists of heated gas between the galaxies and has a peak temperature between 2–15 keV, dependent on the total mass of the cluster. Galaxy clusters should not be confused with star clusters, such as open clusters, which are structures of stars within galaxies, or with globular clusters, which orbit galaxies. Small aggregates of galaxies are referred to as galaxy groups rather than clusters of galaxies; the galaxy groups and clusters can themselves cluster together to form superclusters. Notable galaxy clusters in the nearby Universe include the Virgo Cluster, Fornax Cluster, Hercules Cluster, the Coma Cluster.
A large aggregation of galaxies known as the Great Attractor, dominated by the Norma Cluster, is massive enough to affect the local expansion of the Universe. Notable galaxy clusters in the distant, high-redshift Universe include SPT-CL J0546-5345 and SPT-CL J2106-5844, the most massive galaxy clusters found in the early Universe. In the last few decades, they are found to be relevant sites of particle acceleration, a feature, discovered by observing non-thermal diffuse radio emissions, such as radio halos and radio relics. Using the Chandra X-ray Observatory, structures such as cold fronts and shock waves have been found in many galaxy clusters. Galaxy clusters have the following properties: They contain 100 to 1,000 galaxies, hot X-ray emitting gas and large amounts of dark matter. Details are described in the "Composition" section; the distribution of the three components is the same in the cluster. They have total masses of 1014 to 1015 solar masses, they have a diameter from 2 to 10 Mpc. The spread of velocities for the individual galaxies is about 800–1000 km/s.
There are three main components of a galaxy cluster. They are tabulated below: Stars, Star clusters, Galaxy clusters, Super clusters Abell catalogue Intracluster medium List of Abell clusters
European Southern Observatory
The European Southern Observatory, formally the European Organisation for Astronomical Research in the Southern Hemisphere, is a 16-nation intergovernmental research organization for ground-based astronomy. Created in 1962, ESO has provided astronomers with state-of-the-art research facilities and access to the southern sky; the organisation employs about 730 staff members and receives annual member state contributions of €162 million. Its observatories are located in northern Chile. ESO has operated some of the largest and most technologically advanced telescopes; these include the 3.6 m New Technology Telescope, an early pioneer in the use of active optics, the Very Large Telescope, which consists of four individual 8.2 m telescopes and four smaller auxiliary telescopes which can all work together or separately. The Atacama Large Millimeter Array observes the universe in the millimetre and submillimetre wavelength ranges, is the world's largest ground-based astronomy project to date, it was completed in March 2013 in an international collaboration by Europe, North America, East Asia and Chile.
Under construction is the Extremely Large Telescope. It will use a 39.3-metre-diameter segmented mirror, become the world's largest optical reflecting telescope when operational in 2024. Its light-gathering power will allow detailed studies of planets around other stars, the first objects in the universe, supermassive black holes, the nature and distribution of the dark matter and dark energy which dominate the universe. ESO's observing facilities have made astronomical discoveries and produced several astronomical catalogues, its findings include the discovery of the most distant gamma-ray burst and evidence for a black hole at the centre of the Milky Way. In 2004, the VLT allowed astronomers to obtain the first picture of an extrasolar planet orbiting a brown dwarf 173 light-years away; the High Accuracy Radial Velocity Planet Searcher instrument installed on the older ESO 3.6 m telescope led to the discovery of extrasolar planets, including Gliese 581c—one of the smallest planets seen outside the solar system.
The idea that European astronomers should establish a common large observatory was broached by Walter Baade and Jan Oort at the Leiden Observatory in the Netherlands in spring 1953. It was pursued by Oort, who gathered a group of astronomers in Leiden to consider it on June 21 that year. Thereafter, the subject was further discussed at the Groningen conference in the Netherlands. On January 26, 1954, an ESO declaration was signed by astronomers from six European countries expressing the wish that a joint European observatory be established in the southern hemisphere. At the time, all reflector telescopes with an aperture of 2 metres or more were located in the northern hemisphere; the decision to build the observatory in the southern hemisphere resulted from the necessity of observing the southern sky. Although it was planned to set up telescopes in South Africa, tests from 1955 to 1963 demonstrated that a site in the Andes was preferable. On November 15, 1963 Chile was chosen as the site for ESO's observatory.
The decision was preceded by the ESO Convention, signed 5 October 1962 by Belgium, France, the Netherlands and Sweden. Otto Heckmann was nominated as the organisation's first director general on 1 November 1962. A preliminary proposal for a convention of astronomy organisations in these five countries was drafted in 1954. Although some amendments were made in the initial document, the convention proceeded until 1960 when it was discussed during that year's committee meeting; the new draft was examined in detail, a council member of CERN highlighted the need for a convention between governments. The convention and government involvement became pressing due to rising costs of site-testing expeditions; the final 1962 version was adopted from the CERN convention, due to similarities between the organisations and the dual membership of some members. In 1966, the first ESO telescope at the La Silla site in Chile began operating; because CERN had sophisticated instrumentation, the astronomy organisation turned to the nuclear-research body for advice and a collaborative agreement between ESO and CERN was signed in 1970.
Several months ESO's telescope division moved into a CERN building in Geneva and ESO's Sky Atlas Laboratory was established on CERN property. ESO's European departments moved into the new ESO headquarters in Garching, Germany in 1980. Although ESO is headquartered in Germany, its telescopes and observatories are in northern Chile, where the organisation operates advanced ground-based astronomical facilities: La Silla, which hosts the New Technology Telescope Paranal, where the Very Large Telescope is located Llano de Chajnantor, which hosts the APEX submillimetre telescope and where ALMA, the Atacama Large Millimeter/submillimeter Array, is locatedThese are among the best locations for astronomical observations in the southern hemisphere. An ESO project is the Extremely Large Telescope, a 40-metre-class telescope based on a five-mirror design and the planned Overwhelmingly Large Telescope; the ELT will be the near-infrared telescope in the world. ESO began its design in early 2006, aimed to begin construction in 2012.
Construction work at the ELT site started in June 2014. As decided by the ESO council on 26 April 2010, a fou
Atacama Large Millimeter Array
The Atacama Large Millimeter/submillimeter Array is an astronomical interferometer of 66 radio telescopes in the Atacama Desert of northern Chile, which observe electromagnetic radiation at millimeter and submillimeter wavelengths. The array has been constructed on the 5,000 m elevation Chajnantor plateau - near the Llano de Chajnantor Observatory and the Atacama Pathfinder Experiment; this location was chosen for its high elevation and low humidity, factors which are crucial to reduce noise and decrease signal attenuation due to Earth's atmosphere. ALMA is expected to provide insight on star birth during the early Stelliferous era and detailed imaging of local star and planet formation. ALMA is an international partnership among Europe, the United States, Japan, South Korea and Chile. Costing about US$1.4 billion, it is the most expensive ground-based telescope in operation. ALMA began scientific observations in the second half of 2011 and the first images were released to the press on 3 October 2011.
The array has been operational since March 2013. The initial ALMA array is composed of 66 high-precision antennas, operates at wavelengths of 9.6 to 0.3 millimeters. The array has much higher sensitivity and higher resolution than earlier submillimeter telescopes such as the single-dish James Clerk Maxwell Telescope or existing interferometer networks such as the Submillimeter Array or the Institut de Radio Astronomie Millimétrique Plateau de Bure facility; the antennas can be moved across the desert plateau over distances from 150 m to 16 km, which will give ALMA a powerful variable "zoom", similar in its concept to that employed at the centimetre-wavelength Very Large Array site in New Mexico, United States. The high sensitivity is achieved through the large numbers of antenna dishes that will make up the array; the telescopes were provided by the European, North American and East Asian partners of ALMA. The American and European partners each provided twenty-five 12-meter diameter antennas, that compose the main array.
The participating East Asian countries are contributing 16 antennas in the form of the Atacama Compact Array, part of the enhanced ALMA. By using smaller antennas than the main ALMA array, larger fields of view can be imaged at a given frequency using ACA. Placing the antennas closer together enables the imaging of sources of larger angular extent; the ACA works together with the main array in order to enhance the latter's wide-field imaging capability. ALMA has its conceptual roots in three astronomical projects — the Millimeter Array of the United States, the Large Southern Array of Europe, the Large Millimeter Array of Japan; the first step toward the creation of what would become ALMA came in 1997, when the National Radio Astronomy Observatory and the European Southern Observatory agreed to pursue a common project that merged the MMA and LSA. The merged array combined the sensitivity of the LSA with the frequency coverage and superior site of the MMA. ESO and NRAO worked together in technical and management groups to define and organize a joint project between the two observatories with participation by Canada and Spain.
A series of resolutions and agreements led to the choice of "Atacama Large Millimeter Array", or ALMA, as the name of the new array in March 1999 and the signing of the ALMA Agreement on 25 February 2003, between the North American and European parties. Following mutual discussions over several years, the ALMA Project received a proposal from the National Astronomical Observatory of Japan whereby Japan would provide the ACA and three additional receiver bands for the large array, to form Enhanced ALMA. Further discussions between ALMA and NAOJ led to the signing of a high-level agreement on 14 September 2004 that makes Japan an official participant in Enhanced ALMA, to be known as the Atacama Large Millimeter/submillimeter Array. A groundbreaking ceremony was held on November 6, 2003 and the ALMA logo was unveiled. During an early stage of the planning of ALMA, it was decided to employ ALMA antennas designed and constructed by known companies in North America and Japan, rather than using one single design.
This was for political reasons. Although different approaches have been chosen by the providers, each of the antenna designs appears to be able to meet ALMA's stringent requirements; the components designed and manufactured across Europe were transported by specialist aerospace and astrospace logistics company Route To Space Alliance, 26 in total which were delivered to Antwerp for onward shipment to Chile. ALMA was a 50-50 collaboration between the National Radio Astronomy Observatory and European Southern Observatory and extended with the help of the other Japanese and Chilean partners. ALMA is the largest and most expensive ground-based astronomical project, costing between US$1.4 and 1.5 billion.. PartnersEuropean Southern Observatory and the European Regional Support Centre National Science Foundation via the National Radio Astronomy Observatory and the North American ALMA Science Center National Research Council of Canada National Astronomical Observatory of Japan under the National Institutes of Natural Sciences ALMA-Taiwan at the Academia Sinica Institute of Astronomy & Astrophysics Republic of Chile The complex was built by European, U.
S. Japanese, Canadian co
The parsec is a unit of length used to measure large distances to astronomical objects outside the Solar System. A parsec is defined as the distance at which one astronomical unit subtends an angle of one arcsecond, which corresponds to 648000/π astronomical units. One parsec is equal to 31 trillion kilometres or 19 trillion miles; the nearest star, Proxima Centauri, is about 1.3 parsecs from the Sun. Most of the stars visible to the unaided eye in the night sky are within 500 parsecs of the Sun; the parsec unit was first suggested in 1913 by the British astronomer Herbert Hall Turner. Named as a portmanteau of the parallax of one arcsecond, it was defined to make calculations of astronomical distances from only their raw observational data quick and easy for astronomers. For this reason, it is the unit preferred in astronomy and astrophysics, though the light-year remains prominent in popular science texts and common usage. Although parsecs are used for the shorter distances within the Milky Way, multiples of parsecs are required for the larger scales in the universe, including kiloparsecs for the more distant objects within and around the Milky Way, megaparsecs for mid-distance galaxies, gigaparsecs for many quasars and the most distant galaxies.
In August 2015, the IAU passed Resolution B2, which, as part of the definition of a standardized absolute and apparent bolometric magnitude scale, mentioned an existing explicit definition of the parsec as 648000/π astronomical units, or 3.08567758149137×1016 metres. This corresponds to the small-angle definition of the parsec found in many contemporary astronomical references; the parsec is defined as being equal to the length of the longer leg of an elongated imaginary right triangle in space. The two dimensions on which this triangle is based are its shorter leg, of length one astronomical unit, the subtended angle of the vertex opposite that leg, measuring one arc second. Applying the rules of trigonometry to these two values, the unit length of the other leg of the triangle can be derived. One of the oldest methods used by astronomers to calculate the distance to a star is to record the difference in angle between two measurements of the position of the star in the sky; the first measurement is taken from the Earth on one side of the Sun, the second is taken half a year when the Earth is on the opposite side of the Sun.
The distance between the two positions of the Earth when the two measurements were taken is twice the distance between the Earth and the Sun. The difference in angle between the two measurements is twice the parallax angle, formed by lines from the Sun and Earth to the star at the distant vertex; the distance to the star could be calculated using trigonometry. The first successful published direct measurements of an object at interstellar distances were undertaken by German astronomer Friedrich Wilhelm Bessel in 1838, who used this approach to calculate the 3.5-parsec distance of 61 Cygni. The parallax of a star is defined as half of the angular distance that a star appears to move relative to the celestial sphere as Earth orbits the Sun. Equivalently, it is the subtended angle, from that star's perspective, of the semimajor axis of the Earth's orbit; the star, the Sun and the Earth form the corners of an imaginary right triangle in space: the right angle is the corner at the Sun, the corner at the star is the parallax angle.
The length of the opposite side to the parallax angle is the distance from the Earth to the Sun (defined as one astronomical unit, the length of the adjacent side gives the distance from the sun to the star. Therefore, given a measurement of the parallax angle, along with the rules of trigonometry, the distance from the Sun to the star can be found. A parsec is defined as the length of the side adjacent to the vertex occupied by a star whose parallax angle is one arcsecond; the use of the parsec as a unit of distance follows from Bessel's method, because the distance in parsecs can be computed as the reciprocal of the parallax angle in arcseconds. No trigonometric functions are required in this relationship because the small angles involved mean that the approximate solution of the skinny triangle can be applied. Though it may have been used before, the term parsec was first mentioned in an astronomical publication in 1913. Astronomer Royal Frank Watson Dyson expressed his concern for the need of a name for that unit of distance.
He proposed the name astron, but mentioned that Carl Charlier had suggested siriometer and Herbert Hall Turner had proposed parsec. It was Turner's proposal. In the diagram above, S represents the Sun, E the Earth at one point in its orbit, thus the distance ES is one astronomical unit. The angle SDE is one arcsecond so by definition D is a point in space at a distance of one parsec from the Sun. Through trigonometry, the distance SD is calculated as follows: S D = E S tan 1 ″ S D ≈ E S 1 ″ = 1 au 1 60 × 60 × π
National Radio Astronomy Observatory
The National Radio Astronomy Observatory is a Federally Funded Research and Development Center of the United States National Science Foundation operated under cooperative agreement by Associated Universities, Inc for the purpose of radio astronomy. NRAO designs and operates its own high sensitivity radio telescopes for use by scientists around the world; the NRAO headquarters is located on the campus of the University of Virginia in Charlottesville, Virginia. The North American ALMA Science Center and the NRAO Technology Center and Central Development Laboratory are located in Charlottesville, Virginia. NRAO was, until October 2016, the operator of the world's largest steerable radio telescope, the Robert C. Byrd Green Bank Telescope, which stands near Green Bank, West Virginia; the observatory contains several other telescopes, among them the 140-foot telescope that utilizes an equatorial mount uncommon for radio telescopes, three 85-foot telescopes forming the Green Bank Interferometer, a 40-foot telescope used by school groups and organizations for small scale research, a fixed radio'horn' built to observe the radio source Cassiopeia A, as well as a reproduction of the original antenna built by Karl Jansky while he worked for Bell Labs to detect the interference, discovered to be unknown natural radio waves emitted by the universe.
Green Bank is in the United States National Radio Quiet Zone, coordinated by NRAO for protection of the Green Bank site as well as the Sugar Grove, West Virginia monitoring site operated by the NSA. The zone consists of a 13,000-square-mile piece of land where fixed transmitters must coordinate their emissions before a license is granted; the land was set aside by the Federal Communications Commission in 1958. No fixed radio transmitters are allowed within the area closest to the telescope. All other fixed radio transmitters including TV and radio towers inside the zone are required to transmit such that interference at the antennas is minimized by methods including limited power and using directional antennas. With the advent of wireless technology and microprocessors in everything from cameras to cars, it is difficult to keep the sites free of radio interference. To aid in limiting outside interference, the area surrounding the Green Bank observatory was at one time planted with pines characterized by needles of a certain length to block electromagnetic interference at the wavelengths used by the observatory.
At one point, the observatory faced the problem of North American flying squirrels tagged with US Fish & Wildlife Service telemetry transmitters. Electric fences, electric blankets, faulty automobile electronics, other radio wave emitters have caused great trouble for the astronomers in Green Bank. All vehicles on the premises are powered by diesel motors to minimize interference by ignition systems; the NRAO's facility in Socorro is the Pete V. Domenici Array Operations Center. Located on the New Mexico Tech university campus, the AOC serves as the headquarters for the Very Large Array, the setting for the 1997 movie Contact, is the control center for the Very Long Baseline Array; the ten VLBA telescopes are located in Hawaii, the U. S. Virgin Islands, eight other sites across the continental United States. Offices are located on the University of Arizona campus. NRAO operated the 12 Meter Telescope on Kitt Peak. NRAO suspended operations at this telescope and funding was rerouted to the Atacama Large Millimeter Array instead.
The Arizona Radio Observatory now operates the 12 Meter Telescope. The Atacama Large Millimeter Array site in Chile is at ~5000 m altitude near Cerro Chajnantor in northern Chile; this is about 40 km east of the historic village of San Pedro de Atacama, 130 km southeast of the mining town of Calama, about 275 km east-northeast of the coastal port of Antofagasta. The Karl G. Jansky Lectureship is a prestigious Lecture awarded by the Board of Trustees of the NRAO; the Lectureship is awarded "to recognize outstanding contributions to the advancement of radio astronomy." Recipients have included Fred Hoyle, Charles Townes, Edward M. Purcell, Subrahmanyan Chandrasekhar, Philip Morrison, Vera Rubin, Jocelyn Bell Burnell, Frank J. Low and Mark Reid; the lecture is delivered in Socorro. Official website
A galaxy group or group of galaxies is an aggregation of galaxies comprising about 50 or fewer gravitationally bound members, each at least as luminous as the Milky Way. The groups and clusters of galaxies can themselves be clustered, into superclusters of galaxies; the Milky Way galaxy is part of a group of galaxies called the Local Group. Groups of galaxies are the smallest aggregates of galaxies, they contain no more than 50 galaxies in a diameter of 1 to 2 megaparsecs. Their mass is 1013 solar masses; the spread of velocities for the individual galaxies is about 150 km/s. However, this definition should be used as a guide only, as larger and more massive galaxy systems are sometimes classified as galaxy groups. Groups are the most common structures of galaxies in the universe, comprising at least 50% of the galaxies in the local universe. Groups have a mass range between those of the large elliptical galaxies and clusters of galaxies. In the local universe, about half of the groups exhibit diffuse X-ray emissions from their intracluster media.
Those that emit X-rays appear to have early-type galaxies as members. The diffuse X-ray emissions come from zones within the inner 10-50% of the groups' virial radius 50-500 kpc. There are several subtypes of groups. A compact group consists of a small number of galaxies around five, in close proximity and isolated from other galaxies and formations; the first compact group to be discovered was Stephan's Quintet, found in 1877. Stephan's Quintet is named for a compact group of four galaxies plus an unassociated foreground galaxy. Astronomer Paul Hickson created a catalogue of such groups in the Hickson Compact Groups. Compact groups of galaxies show the effect of dark matter, as the visible mass is less than that needed to gravitationally hold the galaxies together in a bound group. Compact galaxy groups are not dynamically stable over Hubble time, thus showing that galaxies evolve by merger, over the timescale of the age of the universe. Fossil galaxy groups, fossil groups, or fossil clusters are believed to be the end-result of galaxy merging within a normal galaxy group, leaving behind the X-ray halo of the progenitor group.
Galaxies within a group merge. The physical process behind this galaxy-galaxy merger is dynamical friction; the time-scales for dynamical friction on luminous galaxies suggest that fossil groups are old, undisturbed systems that have seen little infall of L* galaxies since their initial collapse. Fossil groups are thus an important laboratory for studying the formation and evolution of galaxies and the intragroup medium in an isolated system. Fossil groups may still contain unmerged dwarf galaxies, but the more massive members of the group have condensed into the central galaxy; the closest fossil group to the Milky Way is NGC 6482, an elliptical galaxy at a distance of 180 million light-years located in the constellation of Hercules. Proto-groups are groups, they are the smaller form of protoclusters. These contain galaxies and protogalaxies embedded in dark matter haloes that are in the process of fusing into group-formations of singular dark matter halos. Illustris project
The Abell catalog of rich clusters of galaxies is an all-sky catalog of 4,073 rich galaxy clusters of nominal redshift z ≤ 0.2. This catalog supplements a revision of George O. Abell's original "Northern Survey" of 1958, which had only 2,712 clusters, with a further 1,361 clusters – the "Southern Survey" of 1989, published after Abell's death by co-authors Harold G. Corwin and Ronald P. Olowin from those parts of the south celestial hemisphere, omitted from the earlier survey; the Abell catalog, its clusters, are of interest to amateur astronomers as challenge objects to be viewed in dark locations on large aperture amateur telescopes. The original catalog of 2,712 rich clusters of galaxies was published in 1958 by George O. Abell, studying at the California Institute of Technology; the catalog, which formed part of Abell's PhD thesis, was prepared by means of a visual inspection of the red 103a-E plates of the Palomar Observatory Sky Survey, for which Abell was one of the principal observers.
A. G. Wilson, another of the principal observers, assisted Abell in the initial stages of the survey by inspecting the plates as they were produced. After the completion of the survey, Abell went over the plates again and carried out a more detailed inspection. In both cases inspection was made with a 3.5× magnifying lens. To qualify for inclusion in the catalog, a cluster had to satisfy four criteria: Richness: A cluster must have a minimum population of 50 members within a magnitude range of m3 to m3+2. To ensure a healthy margin of error, this criterion was not applied rigorously, the final catalog included many clusters with fewer than fifty members. Abell divided the clusters into six "richness groups", depending on the number of galaxies in a given cluster that lie within the magnitude range m3 to m3+2: Group 0: 30–49 galaxies Group 1: 50–79 galaxies Group 2: 80–129 galaxies Group 3: 130–199 galaxies Group 4: 200–299 galaxies Group 5: more than 299 galaxies Compactness: A cluster must be sufficiently compact that its fifty or more members lie within one "counting radius" of the cluster's centre.
This radius, now known as the "Abell radius", may be defined as 1.72/z arcminutes, where z is the cluster's redshift, or as 1.5h−1 Mpc, where the Hubble constant is assumed to beH0 = 100 km s−1 Mpc−1, h is a dimensionless scale parameter which takes value between 0.5 and 1. H = H0/100; the precise value of the Abell radius depends on the value taken for that parameter h. For h = 0.75, the Abell radius is 2 megaparsecs. This is more than twice the estimate Abell gave in 1958, when H0 was thought to be as high as 180 km s−1 Mpc−1. Distance: A cluster should have a nominal redshift of between 0.02 and 0.2. Assuming H0 = 180 km s−1 Mpc−1, these values correspond to distances of about 33 and 330 Mpc respectively, it has since been shown than many of the clusters in the catalog are more remote than this, some being as far away as z = 0.4. Abell divided the clusters into seven "distance groups" according to the magnitudes of their tenth-brightest members: Group 1: mag 13.3–14.0 Group 2: mag 14.1–14.8 Group 3: mag 14.9–15.6 Group 4: mag 15.7–16.4 Group 5: mag 16.5–17.2 Group 6: mag 17.3–18.0 Group 7: mag > 18.0 Galactic latitude: Areas of the sky in the neighbourhood of the Milky Way were excluded from the study because the density of stars in those fields – not to mention interstellar obscuration – made it difficult to positively identify galaxy clusters.
Like the richness criterion, this one was not applied rigorously, several clusters in or close to the Galactic Plane being included in the catalog where Abell was satisfied that they were genuine clusters that met the other criteria. In the catalog as published the clusters were listed in increasing order of right ascension. Equatorial coordinates were given for the equinox of 1855 and galactic coordinates for 1900. Listed for each cluster were the following: the cluster's precession rate the magnitude of the cluster's tenth-brightest member the distance group of the cluster the richness group of the cluster The sky-coverage of the 1958 catalog was limited to declinations north of –27°, the original southern limit of POSS. To rectify this and other shortcomings, the original catalog was revised and supplemented with an additional catalog – the "Southern Survey" – of rich galaxy clusters from those parts of the south celestial hemisphere, omitted from the original catalog; the Southern Survey added a further 1,361 rich clusters to Abell's original Northern Survey.
The deep IIIa-J plates of the Southern Sky Survey were used in the survey. These photographic plates were taken with the United Kingdom's 1.2-metre Schmidt Telescope at Siding Spring Observatory, Australia, in the 1970s. Abell began the survey during a sabbatical year in Edinburgh in 1976. There he enlisted the assistance of Harold G Corwin of the University of Edinburgh, who continued to work on the catalog until 1981, at which time he joined the Department of Astronomy at the University of Texas. By about half the survey had been completed. An interim paper on the Southern Survey was read at a symposium in 1983, about one month before Abell's death.