Corvus (constellation)

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Corvus
Constellation
Corvus
Abbreviation Crv
Genitive Corvi
Pronunciation /ˈkɔrvəs/,
genitive /ˈkɔrv/
Symbolism the Crow/Raven
Right ascension 12
Declination −20
Family Hercules
Quadrant SQ3
Area 184 sq. deg. (70th)
Main stars 4
Bayer/Flamsteed
stars
10
Stars with planets 1
Stars brighter than 3.00m 3
Stars within 10.00 pc (32.62 ly) 1
Brightest star γ Crv (Gienah) (2.59m)
Nearest star Ross 695
(28.99 ly, 8.89 pc)
Messier objects 0
Meteor showers Corvids (June 26)
Bordering
constellations
Virgo
Crater
Hydra
Visible at latitudes between +60° and −90°.
Best visible at 21:00 (9 p.m.) during the month of May.

Corvus is a small constellation in the Southern Celestial Hemisphere. Its name comes from the Latin word "raven" or "crow". It includes only 11 stars with brighter than 4.02 magnitudes. One of the 48 constellations listed by the 2nd-century astronomer Ptolemy, it remains one of the 88 modern constellations. The four brightest stars, Gamma, Delta, Epsilon, and Beta Corvi from a distinctive quadrilateral in the night sky. The young star Eta Corvi has been found to have two debris disks.

History and mythology[edit]

Corvus, Crater, and other constellations seen around Hydra in Urania's Mirror (1825).

The Greek figure of Corvus is modeled on the Babylonian Raven (MUL.UGA.MUSHEN), which was similarly placed sitting on the tail of the Serpent (Greek Hydra). The Babylonian constellation was sacred to Adad, the god of rain and storm; in the second Millennium it would have risen just before the start of the autumnal rainy season.[1]

One myth associated with Corvus is that of Apollo and Coronis. Coronis had been unfaithful to her lover, who learned this information from a pure white crow. Apollo then turned its feathers black in a fit of rage.[2]

Another legend associated with Corvus is that a crow stopped on his way to fetch water for Apollo, in order to eat figs. Instead of telling the truth to Apollo, he lied and said that a snake, Hydra, kept him from the water, while holding a snake in his talons as proof. Apollo saw this to be a lie, however, and flung the crow (Corvus), cup (Crater), and the snake (Hydra) into the sky. He further punished the wayward bird by making sure that it would forever be thirsty, both in real life and in the heavens, where the Cup is barely out of reach.[2]

Equivalents[edit]

In Chinese astronomy, the stars of Corvus are located within the Vermillion Bird of the South (南方朱雀, Nán Fāng Zhū Què).[3] The four main stars depict a chariot, Zhen, while Alpha and Eta mark the linchpins for the wheels, and Zeta is Changsha, a coffin.[4]

In Indian astronomy, the first five stars of Corvus correspond to the Hastā, the 11th nakshatra or lunar mansion.[5]

Corvus was recognized as a constellation by several Polynesian cultures. In the Marquesas Islands, it was called Mee; in Pukapuka, it was called Te Manu, and in the Society Islands, it was called Metua-ai-papa.[6]

Corvus equates to the Bran of Mabinogion fame. The character is mentioned heavily in the Welsh stories, most notably in the second branch. Bendigeidfran (bendigaid + brân) is Welsh for 'blessed raven.'

Characteristics[edit]

Covering 183 square degrees and hence 0.446% of the sky, Corvus ranks 70th of the 88 constellations in area.[7] It is bordered by Virgo to the north and east, Hydra to the south, and Crater to the west. The three-letter abbreviation for the constellation, as adopted by the International Astronomical Union in 1922, is 'Crv'.[8] The official constellation boundaries, as set by Eugène Delporte in 1930, are defined by a polygon of six segments (illustrated in infobox). In the equatorial coordinate system, the right ascension coordinates of these borders lie between 11h 56m 22s and 12h 56m 40s, while the declination coordinates are between -11.68° and -25.20°.[9] Its position in the Southern Celestial Hemisphere means that the whole constellation is visible to observers south of 65°N.[7][a]

Notable features[edit]

The constellation Corvus as it can be seen by the naked eye.

Stars[edit]

The German cartographer Johann Bayer used the Greek letters Alpha through Eta to label the most prominent stars in the constellation. John Flamsteed gave nine stars Flamsteed designations, while one star he designated in the neighbouring constellation Crater—31 Crateris—ended up in Corvus.[10] Within the constellation's borders, there are 29 stars brighter than or equal to apparent magnitude 6.5.[b][7]

Four principal stars, Delta, Gamma, Epsilon, and Beta Corvi, form an asterism known as "the "Spica's Spanker"[12] or "the Sail".[13][14] Gamma and Delta serve as pointers toward Spica. Also called Gienah, Gamma is the brightest star in Corvus at magnitude 2.59.[15] 154±1 light-years from Earth,[16] it is a blue-white hued giant star of spectral type B8III. Its traditional name means "wing",[15] the star marking the left wing in Bayer's Uranometria.[10] Delta Corvi, traditionally called Algorab, is a double star divisible in small amateur telescopes. The primary is a blue-white hued star of magnitude 2.9, 88 light-years from Earth. The secondary is a purple-tinged star of magnitude 9. Its common name means "the raven".[2] It is one of two stars marking the right wing.[10] Beta Corvi is a yellow-hued giant star of spectral type G5II and magnitude 2.7, 146±1 light-years from Earth.[16] It marks the raven's breast.[10]

Also called Alchiba, Alpha Corvi is a white-hued star of spectral type F1V and magnitude 4.0, 48.7 ± 0.1 light-years from Earth.[16] It exhibits periodic changes in its spectrum over a three day period, which suggests it is either a spectroscopic binary or (more likely) a pulsating Gamma Doradus-type variable. If the latter is the case, it is estimated to be 1.39 times as massive as the Sun.[17] According to Bayer's atlas, it lies above the bird's beak.[10]

Also marking the raven's right wing is Eta Corvi,[10] a yellow-white main sequence star that is 1.52 times as massive and 4.87 times as luminous as the Sun. It is 59 light-years distant from our Solar System.[18] Two debris disks have been detected orbiting this star, one warm within 3.5 AU and another out at ~150 AU.[19] [20]

Zeta Corvi marks the raven's neck.[10] It is of apparent magnitude 5.21, separated by 7 arcseconds from the star HR 4691.[21] Located 420 ± 10 light-years distant,[16] it is a blue-white Be star of spectral type B8V, the presence of hydrogen emission lines in its spectrum indicating it has a circumstellar disk. These stars may be an optical double or a true multiple star system, with a separation of at least 50,000 astronomical units and the stars taking 3.5 million years to orbit each other. HR 4691 is itself double, composed of an ageing yellow-orange giant whose spectral type has been calculated at K0 or G3, and an F-type main sequence star.[21]

Struve 1669 is a binary star that is divisible by small amateur telescopes, 280 light-years from Earth. The pair, both white stars, is visible to the naked eye at magnitude 5.2; the primary is of magnitude 5.9 and the secondary is of magnitude 6.0.[2]

31 Crateris (which was originally placed in Crater by Flamsteed) is a 5.26 magnitude star which was once mistaken for a moon of Mercury. It is in reality a remote binary star system with a hot blue-white star of spectral type B1.5V and a companion about which little is known. The two stars orbit each other every 2.9631 days. The primary is possibly a blue straggler of the Hyades group.[22] The primary is around 15.5 times as massive as the Sun and 52262 times as luminous.[23]

VV Corvi is a close spectroscopic binary, its two component stars orbiting each other with a period of 1.46 days.[24] The mass ratio of the two stars is 0.775±0.024.[25] A tertiary companion was discovered during the Two Micron All-Sky Survey.[26]

TT Corvi is a Semiregular variable red giant of spectral type M3III and apparent magnitude 6.48 around 923 light years distant.[27]

Notable deep-sky objects[edit]

Corvus contains no Messier objects. It has several galaxies and a planetary nebular observable with amateur telescopes.[28] The center of Corvus is home to a planetary nebula NGC 4361.[28] The nebula itself resembles a small elliptical galaxy, but the magnitude 13 star at its centre gives away its true nature.

The NGC 4038 Group is a group of galaxies across Corvus and Crater. The group may contain between 13 and 27 galaxies. The best-known member is the Antennae peculiar galaxy, located 0.25 north of 31 Crateris.[29] It consists of two interacting galaxies—NGC 4038 and 4039—that appear to have a heart shape as seen from Earth. The name originates from the huge tidal tails that come off the ends of the two galaxies, formed because of the spiral galaxies' original rotation. Both original galaxies were spiral galaxies and are now experiencing extensive star formation due to the interaction of gas clouds. The galaxies are 45 million light-years from Earth and each has multiple ultraluminous X-ray sources, the source of which is unknown. Astronomers theorize that they may be a rare type of x-ray emitting binary stars or intermediate-mass black holes.[30] The Antennae galaxies appear in a telescope at the 10th magnitude.[2] NGC 4027 is another member of the group, notable for its extended spiral arm, probably due to a past collision. Known as the Ringtail Galaxy, it lies close to 31 Crateris.[29] NGC 4361 is an elliptical galaxy

See also[edit]

Corvus (Chinese astronomy)

Notes[edit]

  1. ^ While parts of the constellation technically rise above the horizon to observers between the 65°N and 78°N, stars within a few degrees of the horizon are to all intents and purposes unobservable.[7]
  2. ^ Objects of magnitude 6.5 are among the faintest visible to the unaided eye in suburban-rural transition night skies.[11]

References[edit]

  1. ^ Babylonian Star-lore by Gavin White, Solaria Pubs, 2008, page 166ff
  2. ^ a b c d e Ridpath & Tirion 2001, pp. 128-130.
  3. ^ (Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 22 日
  4. ^ Ridpath, Ian. "Corvus and Crater". Star Tales. self-published. Retrieved 6 June 2015. 
  5. ^ Allen, Richard Hinckley, (1963): Star Names: Their Lore and Meaning, New York, Dover Publications, p. 182.
  6. ^ Makemson, Maud Worcester (1941). The Morning Star Rises: an account of Polynesian astronomy. Yale University Press. 
  7. ^ a b c d Ian Ridpath. "Constellations: Andromeda–Indus". Star Tales. self-published. Retrieved 9 September 2014. 
  8. ^ Russell, Henry Norris (1922). "The New International Symbols for the Constellations". Popular Astronomy 30: 469. Bibcode:1922PA.....30..469R. 
  9. ^ "Corvus, Constellation Boundary". The Constellations (International Astronomical Union). Retrieved 12 November 2014. 
  10. ^ a b c d e f g Wagman, Morton (2003). Lost Stars: Lost, Missing and Troublesome Stars from the Catalogues of Johannes Bayer, Nicholas Louis de Lacaille, John Flamsteed, and Sundry Others. Blacksburg, Virginia: The McDonald & Woodward Publishing Company. pp. 119, 387, 390–91, 506. ISBN 978-0-939923-78-6. 
  11. ^ Bortle, John E. (February 2001). "The Bortle Dark-Sky Scale". Sky & Telescope. Sky Publishing Corporation. Retrieved 6 June 2015. 
  12. ^ Nickel, J., (1999): Lift Up Your Eyes on High: Understanding the Stars, Christian Liberty Press, p. 53.
  13. ^ Bakich, M. E., (1995): The Cambridge Guide to the Constellations, Cambridge, Cambridge University Press, pp. 21,22.
  14. ^ Mullaney, J., (2007): The Herschel objects and how to observe them <Astronomers' Observing Guides>, Springer, p. 39.
  15. ^ a b Kaler, James B. (Jim) (2004), "Gienah Corvi", Stars (University of Illinois), retrieved 18 March 2015 
  16. ^ a b c d van Leeuwen, F. (2007). "Validation of the New Hipparcos Reduction". Astronomy and Astrophysics 474 (2): 653–64. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. 
  17. ^ Fuhrmann, K.; Chini, R. (2012). "Multiplicity among F-type Stars". The Astrophysical Journal Supplement 203 (2): 20. Bibcode:2012ApJS..203...30F. doi:10.1088/0067-0049/203/2/30. 30. 
  18. ^ Pawellek, Nicole; Krivov, Alexander V.; Marshall, Jonathan P.; Montesinos, Benjamin; Ábrahám, Péter; Moór, Attila; Bryden, Geoffrey; Eiroa, Carlos (2014). "Disk Radii and Grain Sizes in Herschel-resolved Debris Disks". The Astrophysical Journal 792 (1): 19. Bibcode:2014ApJ...792...65P. doi:10.1088/0004-637X/792/1/65. 65. 
  19. ^ Smith, R. et al. (2008). "The nature of mid-infrared excesses from hot dust around Sun-like stars". Astronomy and Astrophysics 485 (3): 897. arXiv:0804.4580. Bibcode:2008A&A...485..897S. doi:10.1051/0004-6361:20078719. 
  20. ^ Wyatt, M. C. et al. (2005). "Submillimeter Images of a Dusty Kuiper Belt around η Corvi". The Astrophysical Journal 620 (1): 492–500. arXiv:astro-ph/0411061. Bibcode:2005ApJ...620..492W. doi:10.1086/426929. 
  21. ^ a b Kaler, James B. (Jim) (26 April 2013), "Zeta Corvi", Stars (University of Illinois), retrieved 18 March 2015 
  22. ^ Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society 389 (2): 869–879, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x. 
  23. ^ Hohle, M. M.; Neuhäuser, R.; Schutz, B. F. (April 2010), "Masses and luminosities of O- and B-type stars and red supergiants", Astronomische Nachrichten 331 (4): 349, arXiv:1003.2335, Bibcode:2010AN....331..349H, doi:10.1002/asna.200911355 
  24. ^ Batten, A. H. (1967). "Sixth catalogue of the orbital elements of spectroscopic binary systems". Publications of the Dominion Astrophysical Observatory, Victoria 13: 119–251. Bibcode:1967PDAO...13..119B. 
  25. ^ Lucy, L. B.; Ricco, E. (March 1979). "The significance of binaries with nearly identical components". Astronomical Journal 84: 401–412. Bibcode:1979AJ.....84..401L. doi:10.1086/112434. 
  26. ^ Tokovinin, A.; Thomas, S.; Sterzik, M.; Udry, S. (2008). "Tertiary companions to close spectroscopic binaries". Multiple Stars Across the H-R Diagram, ESO Astrophysics Symposia. Berlin Heidelberg. p. 129. arXiv:astro-ph/0601518. ISBN 978-3-540-74744-4. 
  27. ^ Tabur, V.; Bedding, T. R. (2009). "Long-term photometry and periods for 261 nearby pulsating M giants". Monthly Notices of the Royal Astronomical Society 400 (4): 1945–61. arXiv:0908.3228. Bibcode:2009MNRAS.400.1945T. doi:10.1111/j.1365-2966.2009.15588.x. 
  28. ^ a b Luginbuhl, Christian B.; Skiff, Brian A. (1998). Observing Handbook and Catalogue of Deep-Sky Objects. Cambridge, United Kingdom: Cambridge University Press. p. 93. ISBN 9780521625562. 
  29. ^ a b O'Meara, Stephen James (2002). The Caldwell Objects. Cambridge University Press. pp. 240–43. ISBN 978-0-521-82796-6. 
  30. ^ Wilkins, Jamie; Dunn, Robert (2006). 300 Astronomical Objects: A Visual Reference to the Universe. Buffalo, New York: Firefly Books. ISBN 978-1-55407-175-3. 

References[edit]

  • Ridpath, Ian; Tirion, Wil (2001), Stars and Planets Guide, Princeton University Press, ISBN 0-691-08913-2 

Coordinates: Sky map 12h 00m 00s, −20° 00′ 00″