Shapley Supercluster
Encyclopedia
The Shapley Supercluster or Shapley Concentration (SCl 124) is the largest concentration of galaxies in our nearby universe that forms a gravitationally interacting unit
, thereby pulling itself together instead of expanding with the universe. It appears as a striking overdensity in the distribution of galaxies in the constellation of Centaurus. It is 650 million light years
away (z=0.046).
In recent times, the Shapley supercluster
was rediscovered by Somak Raychaudhury
, from a survey of galaxies from UK Schmidt Telescope
Sky survey plates, using the Automated Plate Measuring Facility (APM) at the University of Cambridge
in England. In this paper, the Supercluster was named after Harlow Shapley
, in recognition of his pioneering survey of galaxies in which this concentration of galaxies was first seen. Around the same time, Roberto Scaramella and co-workers had also noticed a remarkable concentration of clusters in the Abell catalogue
of clusters of galaxies: they had named it the Alpha concentration.
and his colleagues at the Harvard College Observatory
started a survey of galaxies in the southern sky, using photographic plates obtained at the 24-inch Bruce telescope at Bloemfontein, South Africa. By 1932, Shapley reported the discovery of 76,000 galaxies brighter than 18th apparent magnitude
in a third of the southern sky, based on galaxy counts from his plates. Some of this data was later published as part of the Harvard galaxy counts, intended to map Galactic obscuration and to find the space density of galaxies.
In this catalog, Shapley could see most of the 'Coma-Virgo cloud' (now known to be a superposition of the Coma Supercluster
and the Virgo Supercluster
), but found a 'cloud' in the constellation of Centaurus
to be the most striking concentration of galaxies. He found it particularly interesting because of its great linear dimension, the numerous population and distinctly elongated form. This can be identified with what we now know as the core of the Shapley Supercluster. Shapley estimated the distance to this cloud to be 14 times that to the Virgo cluster
, from the average diameters of the galaxies.
of galaxies (including our Galaxy) is moving with respect to the CMB frame
. This has led many to speculate that the Shapley Supercluster may indeed be one of the major causes of our peculiar motion (the Great Attractor
), and has led to a surge of interest in this supercluster.
Gravitation
Gravitation, or gravity, is a natural phenomenon by which physical bodies attract with a force proportional to their mass. Gravitation is most familiar as the agent that gives weight to objects with mass and causes them to fall to the ground when dropped...
, thereby pulling itself together instead of expanding with the universe. It appears as a striking overdensity in the distribution of galaxies in the constellation of Centaurus. It is 650 million light years
Light Years
Light Years is the seventh studio album by Australian recording artist Kylie Minogue. It was released on 25 September 2000 by Parlophone and Mushroom Records. The album's style was indicative of her return to "mainstream pop dance tunes"....
away (z=0.046).
In recent times, the Shapley supercluster
Supercluster
Superclusters are large groups of smaller galaxy groups and clusters and are among the largest known structures of the cosmos. They are so large that they are not gravitationally bound and, consequently, partake in the Hubble expansion.-Existence:...
was rediscovered by Somak Raychaudhury
Somak Raychaudhury
Dr Somak Raychaudhury isan astrophysicist at the University of Birmingham, England. Besides teaching various courses in Astronomy & Cosmology, and supervising postgraduate research students, Dr Raychaudhury has also been very actively involved in several public outreach activities throughout his...
, from a survey of galaxies from UK Schmidt Telescope
UK Schmidt Telescope
The 1.2 metre UK Schmidt Telescope is operated by the Australian Astronomical Observatory , and located adjacent to the 3.9 metre Anglo-Australian Telescope at Siding Spring Observatory, Australia...
Sky survey plates, using the Automated Plate Measuring Facility (APM) at the University of Cambridge
University of Cambridge
The University of Cambridge is a public research university located in Cambridge, United Kingdom. It is the second-oldest university in both the United Kingdom and the English-speaking world , and the seventh-oldest globally...
in England. In this paper, the Supercluster was named after Harlow Shapley
Harlow Shapley
Harlow Shapley was an American astronomer.-Career:He was born on a farm in Nashville, Missouri, and dropped out of school with only the equivalent of a fifth-grade education...
, in recognition of his pioneering survey of galaxies in which this concentration of galaxies was first seen. Around the same time, Roberto Scaramella and co-workers had also noticed a remarkable concentration of clusters in the Abell catalogue
Abell catalogue
The Abell catalog of rich clusters of galaxies is an all-sky catalog of 4,073 rich galaxy clusters of nominal redshift z 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...
of clusters of galaxies: they had named it the Alpha concentration.
History
In the late 1920s, Harlow ShapleyHarlow Shapley
Harlow Shapley was an American astronomer.-Career:He was born on a farm in Nashville, Missouri, and dropped out of school with only the equivalent of a fifth-grade education...
and his colleagues at the Harvard College Observatory
Harvard College Observatory
The Harvard College Observatory is an institution managing a complex of buildings and multiple instruments used for astronomical research by the Harvard University Department of Astronomy. It is located in Cambridge, Massachusetts, USA, and was founded in 1839...
started a survey of galaxies in the southern sky, using photographic plates obtained at the 24-inch Bruce telescope at Bloemfontein, South Africa. By 1932, Shapley reported the discovery of 76,000 galaxies brighter than 18th apparent magnitude
Apparent magnitude
The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...
in a third of the southern sky, based on galaxy counts from his plates. Some of this data was later published as part of the Harvard galaxy counts, intended to map Galactic obscuration and to find the space density of galaxies.
In this catalog, Shapley could see most of the 'Coma-Virgo cloud' (now known to be a superposition of the Coma Supercluster
Coma Supercluster
The Coma Supercluster is a nearby supercluster of galaxies comprising the Coma Cluster and the Leo Cluster . Located 300 million light-years from Earth, it is in the center of the Great Wall. The Coma Supercluster is the nearest massive cluster of galaxies to our own Virgo Supercluster...
and the Virgo Supercluster
Virgo Supercluster
The Virgo Supercluster or Local Supercluster is the irregular supercluster that contains the Virgo Cluster in addition to the 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...
), but found a 'cloud' in the constellation of Centaurus
Centaurus
Centaurus is a bright constellation in the southern sky. One of the largest constellations, Centaurus was included among the 48 constellations listed by the 2nd century astronomer Ptolemy, and it remains one of the 88 modern constellations.-Stars:...
to be the most striking concentration of galaxies. He found it particularly interesting because of its great linear dimension, the numerous population and distinctly elongated form. This can be identified with what we now know as the core of the Shapley Supercluster. Shapley estimated the distance to this cloud to be 14 times that to the Virgo cluster
Virgo Cluster
The Virgo Cluster is a cluster of galaxies whose center is 53.8 ± 0.3 Mly away in the constellation Virgo. Comprising approximately 1300 member galaxies, the cluster forms the heart of the larger Local Supercluster, of which the Local Group is an outlying member...
, from the average diameters of the galaxies.
Current interest
The Shapley Supercluster lies very close to the direction in which the Local GroupLocal Group
The Local Group is the group of galaxies that includes Earth's galaxy, the Milky Way. The group comprises more than 30 galaxies , with its gravitational center located somewhere between the Milky Way and the Andromeda Galaxy...
of galaxies (including our Galaxy) is moving with respect to the CMB frame
Cosmic microwave background radiation
In cosmology, cosmic microwave background radiation is thermal radiation filling the observable universe almost uniformly....
. This has led many to speculate that the Shapley Supercluster may indeed be one of the major causes of our peculiar motion (the Great Attractor
Great Attractor
The Great Attractor is a gravity anomaly in intergalactic space within the range of the Centaurus Supercluster that reveals the existence of a localised concentration of mass equivalent to tens of thousands of Milky Ways, observable by its effect on the motion of galaxies and their associated...
), and has led to a surge of interest in this supercluster.
See also
- Dark flowDark flowDark flow is an astrophysical term describing a peculiar velocity of galaxy clusters. The actual measured velocity is the sum of the velocity predicted by Hubble's Law plus a small and unexplained velocity flowing in a common direction....
- Great AttractorGreat AttractorThe Great Attractor is a gravity anomaly in intergalactic space within the range of the Centaurus Supercluster that reveals the existence of a localised concentration of mass equivalent to tens of thousands of Milky Ways, observable by its effect on the motion of galaxies and their associated...
- Hydra-Centaurus SuperclusterHydra-Centaurus SuperclusterThe Hydra-Centaurus Supercluster , or the Hydra and Centaurus superclusters, is a supercluster in two parts and the closest neighbour of Milky Way's Virgo Supercluster....
- Norma ClusterNorma clusterThe Norma Cluster is a rich cluster of galaxies located near the center of the Great Attractor. 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...