The Shapley Supercluster 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. A galaxy is a massive gravitationally bound system consisting of Stars an Interstellar medium of gas and dust, and Dark matter It appears as a striking overdensity in the distribution of galaxies in the constellation of Centaurus, approximately 650 million light years from the Milky way.
In recent times, the Shapley supercluster was re-discovered 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. Dr Somak Raychaudhury (born 1962 in Kolkata India is an Astrophysicist. The 12 Metre UK Schmidt Telescope (UKST is operated by the Anglo-Australian Observatory, and located adjacent to the 3 The University of Cambridge (often Cambridge University) located in Cambridge, England, is the second-oldest university in the 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. Harlow Shapley ( November 2 1885 &ndash October 20 1972) was an American Astronomer. 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. The Abell catalog of rich clusters of galaxies is an all-sky catalog of 4073 rich Galaxy clusters of nominal Redshift z = 0 Galaxy groups and clusters are the largest Gravitationally bound objects to have arisen thus far in the process of cosmic structure formation
History: Shapley's galaxy survey
In the late 1920s, Harlow Shapley 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. Harlow Shapley ( November 2 1885 &ndash October 20 1972) was an American Astronomer. 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. The apparent magnitude ( m) of a celestial body is a measure of its Brightness as seen by an observer on Earth, normalized to the value 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. The Coma Supercluster is a nearby Supercluster of Galaxies comprising the Coma Cluster (Abell 1656 and the Leo Cluster (Abell 1367 The Virgo Supercluster or Local Supercluster is the galactic Supercluster that contains the Local Group, the latter containing in its turn Centaurus ( Centaur) is a bright constellation of the southern hemisphere. 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. The Virgo Cluster is a cluster of galaxies at a distance of approximately 59 ± 4 Mly (18
Current interest
The Shapley Supercluster lies very close to the direction in which the Local Group of galaxies (including our Galaxy) is moving with respect to the rest frame of the Universe defined by the Cosmic microwave background radiation. The Local Group is the group of galaxies that includes our galaxy the Milky Way. 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. The Great Attractor is a Gravity anomaly in Intergalactic space within the range of the Centaurus Supercluster that reveals the existence of a localised
External links
- Article on the Shapley Supercluster in the Encyclopedia of Astronomy and Astrophysics
- The distribution of galaxies in the direction of the 'Great Attractor' Somak Raychaudhury Nature 342, 251-255 (1989)
- A marked concentration of galaxy clusters: is this the origin of large-scale motions? R. Scaramella et al. Nature 338, 562 (1989)
- An atlas of the Universe
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