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The Shapley Supercluster or Shapley Concentration (SCl 124) is the largest concentration of
galaxies 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. ...
in our nearby
universe The universe is all of space and time and their contents, including planets, stars, galaxies, and all other forms of matter and energy. The Big Bang theory is the prevailing cosmological description of the development of the universe. Acc ...
that forms a
gravitation In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the stron ...
ally 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 A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the e ...
of
Centaurus Centaurus is a bright constellation in the southern sky. One of the 88 modern constellations by area, largest constellations, Centaurus was included among the 48 constellations listed by the 2nd-century astronomer Ptolemy, and it remains one o ...
. It is 650 million
light-year A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...
s away ( z=0.046).


History

In 1930,
Harlow Shapley Harlow Shapley (November 2, 1885 – October 20, 1972) was an American scientist, head of the Harvard College Observatory (1921–1952), and political activist during the latter New Deal and Fair Deal. Shapley used Cepheid variable stars to estim ...
and his colleagues at the
Harvard College Observatory The Harvard College Observatory (HCO) 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, United St ...
started a survey of galaxies in the southern sky, using photographic plates obtained at the 24-inch Bruce telescope at
Bloemfontein Bloemfontein, ( ; , "fountain of flowers") also known as Bloem, is one of South Africa's three capital cities and the capital of the Free State (province), Free State province. It serves as the country's judicial capital, along with legisla ...
, South Africa. By 1932, Shapley reported the discovery of 76,000 galaxies brighter than 18th
apparent magnitude Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's li ...
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 The Coma Supercluster (SCl 117) is a nearby supercluster of galaxies comprising the Coma Cluster (Abell 1656) and the Leo Cluster (Abell 1367). Located 300 million light-years from Earth, it is in the center of the Great Wall and a part of the C ...
and the
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 itself contains the Milky Way and Andromeda galaxies, as well as others. At least ...
), but found a 'cloud' in the constellation of
Centaurus Centaurus is a bright constellation in the southern sky. One of the 88 modern constellations by area, largest constellations, Centaurus was included among the 48 constellations listed by the 2nd-century astronomer Ptolemy, and it remains one o ...
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 A supercluster is a large group of smaller galaxy clusters or galaxy groups; they are among the largest known structures in the universe. The Milky Way is part of the Local Group galaxy group (which contains more than 54 galaxies), which in turn ...
. Shapley estimated the distance to this cloud to be 14 times that to the
Virgo Cluster The Virgo Cluster is a large cluster of galaxies whose center is 53.8 ± 0.3 Mly (16.5 ± 0.1 Mpc) away in the constellation Virgo. Comprising approximately 1,300 (and possibly up to 2,000) member galaxies, the cluster forms the heart of the lar ...
, from the average diameters of the galaxies. This would place the Shapley Supercluster at a distance of 231 Mpc, based on the current estimate of the distance to Virgo. In recent times, the Shapley Supercluster was named by
Somak Raychaudhury Somak Raychaudhury ( bn, সোমক রায়চৌধুরী) is an Indian astrophysicist. He is the Director of the Inter-University Centre for Astronomy and Astrophysics (IUCAA), Pune. He is on leave from Presidency University, Kol ...
, from a survey of galaxies from
UK Schmidt Telescope The UK Schmidt Telescope (UKST) is a 1.24 metre Schmidt telescope operated by the Australian Astronomical Observatory (formerly the Anglo-Australian Observatory); it is located adjacent to the 3.9 metre Anglo-Australian Telescope at S ...
Sky survey plates, using the Automated Plate Measuring Facility (APM) at the
University of Cambridge , mottoeng = Literal: From here, light and sacred draughts. Non literal: From this place, we gain enlightenment and precious knowledge. , established = , other_name = The Chancellor, Masters and Schola ...
in England. In this paper, the supercluster was named after
Harlow Shapley Harlow Shapley (November 2, 1885 – October 20, 1972) was an American scientist, head of the Harvard College Observatory (1921–1952), and political activist during the latter New Deal and Fair Deal. Shapley used Cepheid variable stars to estim ...
, 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 the Shapley Supercluster in the
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'' ≤ 0.2. This catalog supplements a revision of George O. Abell's original "Northern Survey" of 1958, wh ...
of
clusters of galaxies The observable universe is a ball-shaped 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 the electromagnetic radiation from these obj ...
: they had named it the ''Alpha concentration''.


Current interest

The Shapley Supercluster lies very close to the direction in which the
Local Group The Local Group is the galaxy group that includes the Milky Way. It has a total diameter of roughly , and a total mass of the order of . It consists of two collections of galaxies in a "dumbbell" shape: the Milky Way and its satellites form ...
of galaxies (including our galaxy) is moving with respect to the
cosmic microwave background In Big Bang cosmology the cosmic microwave background (CMB, CMBR) is electromagnetic radiation that is a remnant from an early stage of the universe, also known as "relic radiation". The CMB is faint cosmic background radiation filling all spac ...
(CMB) frame of reference. This has led many to speculate that the Shapley Supercluster may indeed be one of the major causes of our galaxy's
peculiar motion Peculiar motion or peculiar velocity refers to the velocity of an object relative to a ''rest frame'' — usually a frame in which the average velocity of some objects is zero. Galactic astronomy In galactic astronomy, peculiar motion refers to ...
—the
Great Attractor The Great Attractor is a gravitational anomaly in intergalactic space and the apparent central gravitational point of the Laniakea Supercluster. The observed anomalies suggest a localized concentration of mass millions of times more massive than ...
may be another—and has led to a surge of interest in this supercluster. It has been found that the Great Attractor and all the galaxies in our region of the universe (including our galaxy, the
Milky Way The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye ...
) are moving toward the Shapley Supercluster. In 2017 it was proposed that the movement towards attractors like the
Shapley Attractor The Shapley attractor is an attractor located about the Shapley Supercluster. It is opposed to the Dipole Repeller, in the CMB dipole of local galactic flow. It is thought to be the composite contributions of the Shapley Concentration and the ...
in the supercluster creates a relative movement away from underdense areas, that may be visualized as a virtual ''repeller''. This approach enables new ways of understanding and modelling variations in galactic movements. The nearest large underdense area has been labelled the
dipole repeller The dipole repeller is a center of effective repulsion in the large-scale flow of galaxies in the neighborhood of the Milky Way, first detected in 2017. It is thought to represent a large supervoid, the ''Dipole Repeller Void''. The dipole ...
.


See also

* * * * * *


References


External links


Shapley Supercluster
at Atlas of the Universe *
Harvard College Observatory (HCO)
* * * {{DEFAULTSORT:Shapley Supercluster Great Attractor Centaurus (constellation) Galaxy superclusters