Crater (constellation)

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Crater
Constellation
Crater
AbbreviationCrt
GenitiveCrateris
Pronunciation/ˈkrtər/,
genitive /krəˈtrɪs/
Symbolismthe cup
Right ascension11h
Declination−16°
QuadrantSQ2
Area282 sq. deg. (53rd)
Main stars4
Bayer/Flamsteed
stars
12
Stars with planets7
Stars brighter than 3.00m0
Stars within 10.00 pc (32.62 ly)0
Brightest starδ Crt (Labrum) (3.57m)
Messier objects0
Meteor showersEta Craterids
Bordering
constellations
Leo
Sextans
Hydra
Corvus
Virgo
Visible at latitudes between +65° and −90°.
Best visible at 21:00 (9 p.m.) during the month of April.

Crater is a small constellation in the Southern Celestial Hemisphere. Its name means "cup" in Latin. One of the 48 constellations listed by the 2nd-century astronomer Ptolemy, it depicts a cup that has been associated with the god Apollo and is perched on the back of Hydra the water snake.

There is no star brighter than third magnitude. Its two brightest stars, Delta Crateris of magnitude 3.56 and Alpha Crateris of magnitude 4.07, are ageing orange giant stars that are cooler and larger than the Sun. Beta Crateris is a binary star system composed of a white main sequence star and a white dwarf. Seven star systems have been found to host planets. The Crater 2 dwarf galaxy is a nearby satellite galaxy of the Milky Way.

Mythology[edit]

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

In the Babylonian star catalogues dating from at least 1100 BCE, the stars of Crater were possibly incorporated with those of the crow Corvus in the Babylonian Raven (MUL.UGA.MUSHEN). John H. Rogers observed that the adjoining constellation Hydra signified Ningishzida, the god of the underworld in the Babylonian compendium MUL.APIN. He proposed that Corvus and Crater (along with the water snake Hydra) were death symbols and marked the gate to the underworld.[1] These two constellations, along with the eagle Aquila and the fish Piscis Austrinus, were introduced to the Greeks around 500 BCE; they marked the winter and summer solstices respectively. Furthermore, Hydra had been a landmark as it had straddled the celestial equator in antiquity.[2] Corvus and Crater also featured in the iconography of Mithraism, which is thought to have been of middle-eastern origin before spreading into Ancient Greece and Rome.[3]

Crater is identified with a story from Greek mythology in which a crow or raven serves Apollo, and is sent to fetch water, but it rests lazily on the journey, and after finally obtaining the water in a cup, takes back a water snake as an excuse. According to the myth, Apollo saw through the fraud, and angrily cast the crow, cup, and snake, into the sky.[4]

In other cultures[edit]

In Chinese astronomy, the stars of Crater are located within the constellation of the Vermillion Bird of the South (南方朱雀, Nán Fāng Zhū Què).[5] They depict, along with some stars from Hydra, Yi, the Red Bird's wings. Yi also denotes the 27th lunar mansion. Alternatively, Yi depicts a heroic bowman, his bow composed of other stars in Hydra.[6] In the Society Islands, Crater was recognized as a constellation called Moana-ohu-noa-ei-haa-moe-hara.[7]

Characteristics[edit]

Covering 282.4 square degrees and hence 0.685% of the sky, Crater ranks 53rd of the 88 constellations in area.[8] It is bordered by Leo and Virgo to the north, Corvus to the east, Hydra to the south and west, and Sextans to the northwest. The three-letter abbreviation for the constellation, as adopted by the International Astronomical Union in 1922, is 'Crt'.[9] 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 10h 51m 14s and 11h 56m 24s, while the declination coordinates are between −6.66° and −25.20°.[10] Its position in the Southern Celestial Hemisphere means that the whole constellation is visible to observers south of 65°N.[8][a]

Features[edit]

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

Stars[edit]

The German cartographer Johann Bayer used the Greek letters Alpha through Lambda to label the most prominent stars in the constellation. Bode added more, though only Psi Crateris remains in use. John Flamsteed gave 31 stars in Crater and the segment of Hydra immediately below Crater Flamsteed designations, naming the resulting constellation Hydra et Crater. Most of these stars lie in Hydra.[11] The three brightest stars—Delta, Alpha and Gamma Crateris—from a triangle nearby the brighter star Nu Hydrae in Hydra.[12] Within the constellation's borders, there are 33 stars brighter than or equal to apparent magnitude 6.5.[b][8]

Delta Crateris is the brightest star in Crater at magnitude 3.6. Located 163 ± 4 light-years away, [14] It is an orange giant star of spectral type K0III that is 1.0–1.4 times as massive as the Sun. An ageing star, it has cooled and expanded to 22.44 ± 0.28 times the Sun's radius. It is radiating 171.4 ± 9.0 as much luminosity as the Sun from its outer envelope at an effective temperature of 4,408 ± 57 K.[15] Traditionally called Alkes "the cup", Alpha Crateris is an orange-hued star of magnitude 4.1, 141 ± 2 light-years from Earth.[16] With an estimated mass around 1.61 times that of the Sun, it has exhausted its core hydrogen and expanded to 12 or 13 times the Sun's diameter,[17] shining with 69 times its luminosity.and a surface temperature of 4645 K.[18]

With an apparent magnitude of 4.5, Beta Crateris is a binary system, consisting of white-hued giant star of spectral type A1III and a white dwarf of spectral type DA1.4,[19] 296 ± 8 light-years from Earth.[20] The Hubble Space Telescope was unable to make out the two stars as separate objects.[21] Gamma Crateris is a double star divisible in small amateur telescopes.[22] The primary is a white main sequence star of spectral type A7V that is an estimated 1.81 times as massive as the Sun,[23] while the secondary—of magnitude 9.6—has 75% the Sun's mass,[23] and is likely an orange dwarf.[24] The system is 85.6 ± 0.8 light-years away from Earth.[25]

Epsilon Crateris is the largest of the constellation's brighter stars.[26] An evolved K-type giant star with a stellar classification of K5 III,[27] it has about the same mass as the Sun, but has expanded to 44.7 times the Sun's radius.[28] The star is radiating 391 times the solar luminosity.[29] It is 366 ± 8 light-years distant from Earth.[30]

Zeta Crateris is a binary star system. The primary, component A, is a magnitude 4.95 evolved giant star with a stellar classification of G8 III.[31]It is a red clump star that is generating energy through the fusion of helium at its core.[32] Zeta Crateris has expanded to 13 times the radius of the Sun,[33] and shines with 157 times the luminosity of the Sun.[29] The secondary, component B, is a magnitude 7.84 star.[34] Zeta Crateris is a confirmed member of the Sirius supercluster[35] and is a candidate member of the Ursa Major Moving Group, a collection of stars that share a similar motion through space and may have at one time been members of the same open cluster.[36]The system is located 326 ± 9 light years from the Sun.[37]

Located near Alkes is the red-hued R Crateris,[12] a semiregular variable star of type SRb and a spectral classification of M7. It has a magnitude of 9.8-11.2 and an optical period of 160 days.[citation needed] It is 770 ± 40 light-years distant from Earth.[38]

SZ Crateris is a magnitude 8.5 BY Draconis type variable star. It is a nearby star system located about 42.9 ± 1.0 light years from the Sun,[39] and is a member of the Ursa Major Moving Group.[36]

TT Crateris is a cataclysmic variable; a binary system composed of a white dwarf around as massive as the Sun in close orbit with an orange dwarf of spectral type K5V, the two orbiting each other every 6 hours 26 minutes. The white dwarf strips matter off its companion star, forming an accretion disc which periodically ignites and erupts. The star system has an apparent magnitude of 15.9 when quiescent, brightening to 12.7 in outburst.[40]

HD 98800, also known as TV Crateris, is a quadruple star system with two pairs of young stars. One pair has a debris disk orbiting the both.

HD 96167 is a star 1.31 ± 0.09 times as massive as the Sun that has most likely exhausted its core hydrogen and begun expanding and cooling into a yellow subgiant with a diameter 1.86 ± 0.07 times that of the Sun, and 3.4 ± 0.2 times its luminosity. Analysis of its radial velocity revealed it has a planet with a minimum mass 68% that of Jupiter that takes 498.9 ± 1.0 days to complete an orbit. The orbit itself is highly eccentric, the planet ranging between 0.38 and 2.22 au from its star.[41] The stellar system is 279 ± 1 light-years away from Earth.[42]

HD 98649 is a yellow main sequence star, classified as a G4V, that has the same mass and diameter as the Sun, but has only 86% of its luminosity. In 2012, a long-period ( 4951+607
−465
days) planet companion at least 6.8 times as massive as Jupiter was deduced by radial velocity. Its orbit was calculated to be highly eccentric, swinging out to 10.6 au away from its star, and hence a candidate for direct imaging.[43]

BD-10°3166 is a metallic orange main sequence star of spectral type K3.0V, 268 ± 10 light-years distant from earth.[44] It was found to have a hot Jupiter-type planet that has a minimum mass of 48% of Jupiter's, and takes only 3.49 days to complete an orbit.[45]

WASP-34 is a sunlike star of spectral type G5V that has 1.01 ± 0.07 times the mass and 0.93 ± 0.12 times the diameter of the Sun. It has a planet 0.59 ± 0.01 times as massive as Jupiter that takes 4.317 days to complete an orbit.[46] The system is 432 ± 3 light-years distant from Earth.[47]

DENIS-P J1058.7-1548 is a brown dwarf.

Deep-sky objects[edit]

The Crater 2 dwarf galaxy is a satellite galaxy of the Milky Way,[48] located approximately 380,000 ly from Earth.[49]

NGC 3511 is a spiral galaxy with a slight bar, seen nearly from the edge, of type SBbc. It is a member of the galaxy cluster Abell 1060. This galaxy is magnitude 12, and is 4' × 1' in size. Right nearby, 30" away, is NGC 3513, another SB-class spiral.

NGC 3887 is a barred-spiral galaxy of type SBc, magnitude 11, with a diameter of 3.5'.

NGC 3981 is a spiral galaxy with two wide spiral arms, of type SBbc. It is magnitude 12 with a diameter of 3'. This galaxy was discovered by William Herschel in 1785.

RX J1131 is a quasar located 6 billion light years away from Earth. The black hole in the center of the quasar was the first black hole whose spin has ever been directly measured.[50]

Namesakes[edit]

USS Crater (AK-70) was a United States Navy Crater class cargo ship named after the constellation.

Notes[edit]

  1. ^ While parts of the constellation technically rise above the horizon to observers between the 65°N and 83°N, stars within a few degrees of the horizon are to all intents and purposes unobservable.[8]
  2. ^ Objects of magnitude 6.5 are among the faintest visible to the unaided eye in suburban-rural transition night skies.[13]

References[edit]

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  2. ^ Frank, Roslyn M. (2015). "10: Origins of the "Western" Constellations". Handbook of Archaeoastronomy and Ethnoastronomy. New York, New York: Springer. pp. 147–63.
  3. ^ Rogers, John H. (1998). "Origins of the Ancient Constellations: II. The Mediterranean traditions". Journal of the British Astronomical Association. 108: 79–89. Bibcode:1998JBAA..108...79R.
  4. ^ Ridpath & Tirion 2001, p. 128.
  5. ^ (in Chinese)AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 5 月 31 日
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  • Makemson, Maud Worcester (1941). The Morning Star Rises: an account of Polynesian astronomy. Yale University Press.
  • Ridpath, Ian; Tirion, Wil (2001), Stars and Planets Guide, Princeton University Press, ISBN 0-691-08913-2
  • Ian Ridpath and Wil Tirion (2007). Stars and Planets Guide, Collins, London. ISBN 978-0-00-725120-9. Princeton University Press, Princeton. ISBN 978-0-691-13556-4.
  • Richard Hinckley Allen, The Stars, Their Lore and Legend, New York, Dover.

External links[edit]

Coordinates: Sky map 11h 00m 00s, −16° 00′ 00″