Shapley superclusters
The Shapley supercluster ( SCl 124 ) represents the largest known collection of star systems ( galaxies ) at a distance of up to 700 million light years . It is a center of mass, which ensures that the star systems belonging to it are held together by gravitational forces so that no increase in the distances between the galaxies due to the general expansion of the universe can be observed in its sphere of influence.
The Shapley supercluster appears as a distinct concentration of star systems in the constellation Centaur . Its distance from the Milky Way is about 650 million light years ( redshift : z = 0.046).
The structure of the Shapley supercluster was (re) discovered by Somak Raychaudhury during a survey of the starry sky. Raychaudhury examined photographic plates with images of the southern starry sky using an automated screening system ( APM ) at the University of Cambridge . In his treatise, he named the structure found after the astronomer Harlow Shapley , who first found this cluster of galaxies during an earlier survey of the starry sky. Around the same time, astronomers working with Roberto Scaramella identified this concentration of star systems as a remarkable structure in the cosmos and called it the alpha concentration .
Discovery story
In the late 1920s, Harlow Shapley and colleagues at the Harvard University Observatory began a search for galaxies in the southern skies, evaluating photographic plates taken with the 24-inch Bruce telescope in Bloemfontein , South Africa. In 1932, based on the evaluation, Shapley reported the identification of at least 76,000 galaxies brighter than +18 mag in a third of the southern sky. Some of this data was later published as part of the Harvard Galaxy Censuses, which were conducted to determine the density and distribution of star systems in space.
In the catalog, Shapley listed most of the systems of the "Coma Virgo Cloud" (which is now defined as the overlap zone of the Virgo supercluster and the Coma supercluster ), and he found another "cloud" in the constellation Centaur , which he called overwhelming Concentration of galaxies described. This concentration impressed him because of its enormous size, the number of star systems and the elongated shape. This characterization coincides with the region of the cosmos known today as the core area of the Shapley supercluster. Shapley estimated the distance to the structure to be 14 times the distance to the Virgo supercluster, based on the average apparent diameter of the observed star systems. Based on the current distance estimate for the Virgo supercluster, this results in a distance of 231 megaparsecs (753 million light years).
Current research
The Shapley supercluster extends in the direction of the putative motion vector on which the Local Group , to which our Milky Way belongs, moves through the cosmos. This suggests that the Shapley supercluster could be a major cause of the movement of the local group, whereas previously the structure of the large attractor as a possible center of mass was solely responsible for it. This new assessment has sparked intense scrutiny of the Shapley supercluster.
See also
Individual evidence
- ↑ 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)