Shapley-Ames Catalog

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The Shapley-Ames Catalog of Bright Galaxies is a catalog of galaxies published in 1932 that includes observations of 1249 objects brighter than 13.2 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 Catalogue. [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]

Harlow Shapley American astronomer

Harlow Shapley was a 20th-century American scientist, head of the Harvard College Observatory (1921–1952), and political activist during the latter New Deal and Fair Deal.

Adelaide Ames 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 Thirteenth Magnitude, which was later known as the Shapley-Ames catalog. Ames was a member of the American Astronomical Society. She was a contemporary of Cecilia Payne-Gaposchkin and her closest friend at the observatory.

<i>New General Catalogue</i> astronomical catalogue of deep sky objects

The New General Catalogue of Nebulae and Clusters of Stars is a catalogue of deep-sky objects compiled by John Louis Emil Dreyer in 1888. It expands upon the cataloguing work of William and Caroline Herschel, and John Herschel's General Catalogue of Nebulae and Clusters of Stars. The NGC contains 7,840 objects, known as the NGC objects. It is one of the largest comprehensive catalogues, as it includes all types of deep space objects, including galaxies, star clusters, emission nebulae and absorption nebulae. Dreyer also published two supplements to the NGC in 1895 and 1908, known as the Index Catalogues, describing a further 5,386 astronomical objects.

Contents

History

Shapley and Ames began their study of 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 galaxy clusters, and called this Virgo cloud in the northern hemisphere a "Local Supercluster". [6]

Isotropy is uniformity in all orientations; it is derived from the Greek isos and tropos. Precise definitions depend on the subject area. Exceptions, or inequalities, are frequently indicated by the prefix an, hence anisotropy. Anisotropy is also used to describe situations where properties vary systematically, dependent on direction. Isotropic radiation has the same intensity regardless of the direction of measurement, and an isotropic field exerts the same action regardless of how the test particle is oriented.

Supercluster gravitationally-unbound collection of galaxy groups and clusters

A supercluster is a large group of smaller galaxy clusters or galaxy groups; it is among the largest-known structures of the cosmos. The Milky Way is part of the Local Group galaxy group, which in turn is part of the Laniakea Supercluster. This supercluster spans over 500 million light-years, while the Local Group spans over 10 million light-years. The number of superclusters in the observable universe is estimated to be 10 million.

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.

Allan Sandage astrophysicist

Allan Rex Sandage 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 constant and the age of the universe.

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Virgo Supercluster supercluster, comtaining the Virgo Cluster and the Local Group, including our Milky Way

The Virgo Supercluster or the Local Supercluster is a mass concentration of galaxies containing the Virgo Cluster and Local Group, which in turn contains the Milky Way and Andromeda galaxies. At least 100 galaxy groups and clusters are located within its diameter of 33 megaparsecs. The Virgo SC is one of about 10 million superclusters in the observable universe and is in the Pisces–Cetus Supercluster Complex, a galaxy filament.

Coma Berenices constellation in the northern celestial hemisphere

Coma Berenices is an ancient asterism in the northern sky which has been defined as one of the 88 modern constellations. It is located in the fourth galactic quadrant, between Leo and Boötes, and is visible in both hemispheres. Its name means "Berenice's Hair" in Latin and refers to Queen Berenice II of Egypt, who sacrificed her long hair as a votive offering. It was introduced to Western astronomy during the third century BC by Conon of Samos and was further corroborated as a constellation by Gerardus Mercator and Tycho Brahe. Coma Berenices is the only modern constellation named for a historic person.

Horologium (constellation) constellation in the southern celestial hemisphere

Horologium is a faint constellation in the southern sky. It was devised by French astronomer Nicolas Louis de Lacaille in 1752, and it remains one of the 88 modern constellations. The constellation's brightest star is Alpha Horologii, an orange giant. R Horologii is a red giant Mira variable with one of the widest ranges in brightness known. Three star systems have exoplanets, while Nu Horologii has a debris disk.

Virgo Cluster galaxy cluster

The Virgo Cluster is a cluster of galaxies whose center is 53.8 ± 0.3 Mly away in the constellation Virgo. Comprising approximately 1300 member galaxies, the cluster forms the heart of the larger Virgo Supercluster, of which the Local Group is an outlying member. The Local Group actually experiences the mass of the Virgo Supercluster as the Virgocentric flow. It is estimated that the Virgo Cluster's mass is 1.2×1015M☉ out to 8 degrees of the cluster's center or a radius of about 2.2 Mpc.

Messier 90 Galaxy

Messier 90 is an intermediate spiral galaxy exhibiting a weak inner ring structure about 60 million light-years away in the constellation Virgo. It was discovered by Charles Messier in 1781.

SN 2004dj supernova

SN 2004dj was the brightest supernova since SN 1987A at the time of its discovery.

Messier 98 galaxy in the constellation Coma Berenices

Messier 98, also known as M98 or NGC 4192, is an intermediate spiral galaxy located about 44.4 million light-years away in the constellation Coma Berenices, about 6° to the east of the bright star Denebola. It was discovered by French astronomer Pierre Méchain on 15 March 1781, along with nearby M99 and M100, and was cataloged by French astronomer Charles Messier on 13 April 1781 in his Catalogue des Nébuleuses & des amas d'Étoiles. Messier 98 has a blue shift and is approaching us at about 140 km/s.

Shapley Supercluster Largest concentration of galaxies in our local universe

The Shapley Supercluster or Shapley Concentration 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. It appears as a striking overdensity in the distribution of galaxies in the constellation of Centaurus. It is 650 million light years away (z=0.046).

M96 Group galaxy cluster

The M96 Group is a group of galaxies in the constellation Leo. This group contains between 8 and 24 galaxies, including three Messier objects. The group is one of many groups that lies within the Virgo Supercluster.

NGC 2685 polar-ring galaxy

NGC 2685 is a lenticular and polar ring Seyfert Type 2 galaxy in the constellation Ursa Major. It is about 50,000 light-years across and about 42 million light-years away from Earth. It is receding from Earth at 883 kilometers per second. It is an object of great scientific interest, because polar-ring galaxies are very rare galaxies. They are thought to form when two galaxies gravitationally interact with each other. "The bizarre configuration could be caused by the chance capture of material from another galaxy by a disk galaxy, with the captured debris strung out in a rotating ring. Still, observed properties of NGC 2685 suggest that the rotating ring structure is remarkably old and stable."

NGC 4206 spiral galaxy in the constellation Virgo

NGC 4206 is a spiral galaxy located about 70 million light-years away from Earth in the constellation of Virgo. The galaxy is visible with most moderate amateur telescopes at 13th magnitude. It was discovered by British astronomer William Herschel on 17 April 1784 and is a member of the Virgo Cluster.

NGC 4457 galaxy

NGC 4457 is a spiral galaxy located about 55 million light-years away in the constellation of Virgo. It is also classified as a LINER galaxy, a class of active galaxy defined by their spectral line emissions. NGC 4457 Is inclined by about 33°. It was discovered by astronomer William Herschel on February 23, 1784. Despite being listed in the Virgo Cluster Catalog as VCC 1145, NGC 4457 is a member of the Virgo II Groups which form an extension of the Virgo cluster.

NGC 4586 galaxy

NGC 4586 is a spiral galaxy located about 50 million light-years away in the constellation Virgo. The galaxy was discovered by astronomer William Herschel on February 2, 1786. Although listed in the Virgo Cluster Catalog, NGC 4586 is considered to be a member of the Virgo II Groups which form a southern extension of the Virgo cluster. NGC 4586 is currently in the process of infalling into the Virgo Cluster and is predicted to enter the cluster in about 500 million years.

NGC 4212 galaxy

NGC 4212 is a flocculent spiral galaxy with LINER activity located about 53 million light-years away in the constellation Coma Berenices. The galaxy was discovered by astronomer William Herschel on April 8, 1784 and was listed in the NGC catalog as NGC 4208. He then observed the same galaxy and listed it as NGC 4212. Astronomer John Louis Emil Dreyer later concluded that NGC 4208 was identical to NGC 4212. NGC 4212 is a member of the Virgo Cluster.

NGC 4267 galaxy

NGC 4267 is a barred lenticular galaxy located about 55 million light-years away in the constellation Virgo. It was discovered by astronomer William Herschel on Apr 17, 1784 and is a member of the Virgo Cluster.

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.


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