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Corona Australis is a constellation in the Southern Celestial Hemisphere. Its Latin name means "southern crown", and it is the southern counterpart of Corona Borealis, the northern crown. It is one of the 48 constellations listed by the 2nd-century astronomer Ptolemy, and it remains one of the 88 modern constellations. The Ancient Greeks saw Corona Australis as a wreath rather than a crown and associated it with Sagittarius or Centaurus. Other cultures have likened the pattern to a turtle, ostrich nest, a tent, or even a hut belonging to a rock hyrax.
A galaxy is a system of stars, stellar remnants, interstellar gas, dust, and dark matter bound together by gravity. The word is derived from the Greek galaxias (γαλαξίας), literally 'milky', a reference to the Milky Way galaxy that contains the Solar System. Galaxies, averaging an estimated 100 million stars, range in size from dwarfs with less than a thousand stars, to the largest galaxies known – supergiants with one hundred trillion stars, each orbiting its galaxy's center of mass. Most of the mass in a typical galaxy is in the form of dark matter, with only a few percent of that mass visible in the form of stars and nebulae. Supermassive black holes are a common feature at the centres of galaxies.
The New General Catalogue of Nebulae and Clusters of Stars 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 emission nebulae. Dreyer published two supplements to the NGC in 1895 and 1908, known as the Index Catalogues, describing a further 5,386 astronomical objects. Thousands of these objects are best known by their NGC or IC numbers, which remain in widespread use.
The following is a timeline of galaxies, clusters of galaxies, and large-scale structure of the universe.
Messier 100 is a grand design intermediate spiral galaxy in the southern part of the mildly northern Coma Berenices. It is one of the brightest and largest galaxies in the Virgo Cluster and is approximately 55 million light-years from our galaxy, its diameter being 107,000 light years, and being about 60% as large. It was discovered by Pierre Méchain in 1781 and 29 days later seen again and entered by Charles Messier in his catalogue "of nebulae and star clusters". It was one of the first spiral galaxies to be discovered, and was listed as one of fourteen spiral nebulae by Lord William Parsons of Rosse in 1850. NGC 4323 and NGC 4328 are satellite galaxies of M100; the former is connected with it by a bridge of luminous matter.
The Local Supercluster is a formerly defined supercluster containing the Virgo Cluster and Local Group, which itself contains the Milky Way and Andromeda galaxies, as well as others. 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 is an ancient asterism in the northern sky, which has been defined as one of the 88 modern constellations. It is in the direction of the fourth galactic quadrant, between Leo and Boötes, and it 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. It is the only modern constellation named after a historic person.
Lynx is a constellation named after the animal, usually observed in the Northern Celestial Hemisphere. The constellation was introduced in the late 17th century by Johannes Hevelius. It is a faint constellation, with its brightest stars forming a zigzag line. The orange giant Alpha Lyncis is the brightest star in the constellation, and the semiregular variable star Y Lyncis is a target for amateur astronomers. Six star systems have been found to contain planets. Those of 6 Lyncis and HD 75898 were discovered by the Doppler method; those of XO-2, XO-4, XO-5 and WASP-13 were observed as they passed in front of the host star.
The Virgo Cluster is a large cluster of galaxies whose center is 53.8 ± 0.3 Mly away in the constellation Virgo. Comprising approximately 1,300 member galaxies, the cluster forms the heart of the larger Virgo Supercluster, of which the Local Group is a 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 58 is an intermediate barred spiral galaxy with a weak inner ring structure located within the constellation Virgo, approximately 68 million light-years away from Earth. It was discovered by Charles Messier on April 15, 1779 and is one of four barred spiral galaxies that appear in Messier's catalogue. M58 is one of the brightest galaxies in the Virgo Cluster. From 1779 it was arguably the farthest known astronomical object until the release of the New General Catalogue in the 1880s and even more so the publishing of redshift values in the 1920s.
Messier 90 is an intermediate spiral galaxy exhibiting a weak inner ring structure about 60 million light-years away[a] in the constellation Virgo. It was discovered by Charles Messier in 1781.
Messier 98, M98 or NGC 4192, is an intermediate spiral galaxy about 44.4 million light-years away in slightly northerly Coma Berenices, about 6° to the east of the bright star Denebola. It was discovered by French astronomer Pierre Méchain on 1781, along with nearby M99 and M100, and was catalogued by compatriot Charles Messier 29 days later in his Catalogue des Nébuleuses & des amas d'Étoiles. It has a blueshift, denoting ignoring of its fast other movement, it is approaching at about 140 km/s.
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).
Adelaide Ames was an American astronomer and research assistant at Harvard University. She was best known for her work on detailed surveys of the brightest extra-galactic spiral nebulae. 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.
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 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.
Antoinette de Vaucouleurs was an astronomer who worked in the Astronomy Department of the University of Texas at Austin for 25 years (1961-1986) when few women worked in the field. In addition to ongoing collaborations with her husband, Gérard de Vaucouleurs, she carried out her own research in spectroscopy. Her contributions were recognized in a festschrift in 1988, entitled The World of Galaxies.
ESO 383-76 is an elongated, X-ray luminous supergiant elliptical galaxy, residing as the dominant, brightest cluster galaxy (BCG) of the Abell 3571 galaxy cluster, the sixth-brightest in the sky at X-ray wavelengths. It is located at the distance of 200.6 megaparsecs from Earth, and is possibly a member of the large Shapley Supercluster. With a diameter of about 540.9 kiloparsecs, it is one of the largest galaxies known. It also contains a supermassive black hole, one of the most massive known with mass estimates varying from 2 billion M☉ to 28 billion M☉.
References
- ↑ 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.
- ↑ Steinicke. Observing and Cataloguing Nebulae and Star Clusters. Cambridge University Press. p. 467. ISBN 978-1-139-49010-8.
- 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.
- 1 2 Vera C. Rubin (1997). Bright Galaxies, Dark Matters. Springer. p. 89. ISBN 978-1-56396-231-8.
- ↑ 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.
- ↑ Wolfgang Steinicke (2007). Galaxies and How to Observe Them . Springer. pp. 45. ISBN 978-1-85233-752-0.