Shapley-Ames Catalog

The Shapley-Ames Catalog of Bright Galaxies is a catalog of galaxies published in 1932 that includes observations of 1249 objects brighter than 13.2th magnitude.[1] It was compiled by Harlow Shapley and Adelaide Ames. They identified 1189 objects based on the New General Catalogue and 48 based on the Index Catalog.[2] 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 redshifts and galaxy types.[3]

History

Shapley and Ames began the study all nearby galaxies in 1926.[3]

An important finding from this research was that the galaxies were not evenly distributed (they violated the isotropy assumption) in that the northern hemisphere contained more galaxies than the southern hemisphere.[4] It also found that the Virgo cloud extended further than previously believed.[5] From this data, Shapley and Ames therefore created a new hierarchy of clusters called a supercluster, which is a cluster of a cluster (e.g., a cluster of galaxies), and called this Virgo cloud in the northern hemisphere a "Local Supercluster".[6]

Revised Shapley-Ames Catalog

In 1981, Allan Sandage and Gustav Tammann published an updated version known as the Revised Shapley-Ames Catalog (RSA).[4] 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

  1. ↑ Albrecht Unsöld; Bodo Baschek (1 January 2001). The New Cosmos: An Introduction to Astronomy and Astrophysics. Springer. p. 402. ISBN 978-3-540-67877-9.
  2. ↑ Steinicke. Observing and Cataloguing Nebulae and Star Clusters. Cambridge University Press. p. 467. ISBN 978-1-139-49010-8.
  3. 1 2 Allan Sandage (2004). Centennial History of the Carnegie Institution of Washington: Volume 1, The Mount Wilson Observatory: Breaking the Code of Cosmic Evolution. Cambridge University Press. pp. 491–2. ISBN 978-0-521-83078-2.
  4. 1 2 Vera C. Rubin (1997). Bright Galaxies, Dark Matters. Springer. p. 89. ISBN 978-1-56396-231-8.
  5. ↑ Ronald Newbold Bracewell (1 January 1959). Paris Symposium on Radio Astronomy, Held from 30 July to 6 August 1958. Stanford University Press. pp. 351–. ISBN 978-0-8047-0571-4.
  6. ↑ Wolfgang Steinicke (2007). Galaxies and How to Observe Them. Springer. p. 45. ISBN 978-1-85233-752-0.
This article is issued from Wikipedia - version of the Thursday, September 11, 2014. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.