The ''Shapley-Ames Catalog of Bright Galaxies'' is a catalog 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. ...

published in 1932 that includes observations of 1249 objects brighter than 13.2 magnitude. It was compiled by

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

Adelaide Ames Adelaide Ames (June 3, 1900 – June 26, 1932) was an American astronomer and research assistant at Harvard University. She contributed to the study of galaxies with her co-authorship of ''A Survey of the External Galaxies Brighter Than the Thirt ...

. They identified 1189 objects based on the

New General Catalogue The ''New General Catalogue of Nebulae and Clusters of Stars'' (abbreviated NGC) is an astronomical catalogue of deep-sky objects compiled by John Louis Emil Dreyer in 1888. The NGC contains 7,840 objects, including galaxies, star clusters and ...

and 48 based on the

Index Catalogue The ''New General Catalogue of Nebulae and Clusters of Stars'' (abbreviated NGC) is an astronomical catalogue of deep-sky objects compiled by John Louis Emil Dreyer in 1888. The NGC contains 7,840 objects, including galaxies, star clusters and em ...

. With the help of new photographic recordings, which also contained comparison stars of known brightness, the brightness of many galaxies were measured and recorded only up to a magnitude of 13.2. It was the first compilation of bright galaxies in the northern and southern sky. The catalog contains position, brightness, size, and Hubble classification of the galaxies. For the next 60 years, astronomers referred to this catalog as a primary source for information about

redshift In physics, a redshift is an increase in the wavelength, and corresponding decrease in the frequency and photon energy, of electromagnetic radiation (such as light). The opposite change, a decrease in wavelength and simultaneous increase in f ...

s and galaxy types.

History

Shapley and Ames began their study of all nearby galaxies in 1926. An important finding from this research was that the galaxies were not evenly distributed (they violated the

isotropy Isotropy is uniformity in all orientations; it is derived . Precise definitions depend on the subject area. Exceptions, or inequalities, are frequently indicated by the prefix ' or ', hence ''anisotropy''. ''Anisotropy'' is also used to describe ...

assumption) in that the northern hemisphere contained more galaxies than the southern hemisphere. It also found that the Virgo cloud extended further than previously believed. From this data, Shapley and Ames therefore created a new hierarchy of clusters called a

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 ...

, which is a cluster of galaxy clusters, and called this Virgo cloud in the northern hemisphere a "Local Supercluster".

Revised Shapley-Ames Catalog

In 1981,

Allan Sandage Allan Rex Sandage (June 18, 1926 – November 13, 2010) was an American astronomer. He was Staff Member Emeritus with the Carnegie Observatories in Pasadena, California. He determined the first reasonably accurate values for the Hubble consta ...

and

Gustav Tammann Gustav Andreas Tammann (24 July 1932 – 6 January 2019) was a German astronomer and academic. He served as director of the Astronomical Institute of the University of Basel; as a member of the European Space Agency Space Telescope Advisory Tea ...

published an updated version known as the ''Revised Shapley-Ames Catalog'' (RSA). The original list of galaxies was maintained, with the exception of three objects which were no longer considered galaxies. The information on the 1246 individual galaxies have been updated and substantially extended.

References

Astronomical catalogues Astronomical catalogues of galaxies Astronomical catalogues of galaxy clusters {{astronomical-catalogue-stub