Crater (constellation)

Crater
Constellation

Abbreviation Crt
Genitive Crateris
Pronunciation /ˈkreɪtər/,
genitive /krəˈtɪərᵻs/
Symbolism the cup
Right ascension 11
Declination −16
Family Hercules
Quadrant SQ2
Area 282 sq. deg. (53rd)
Main stars 4
Bayer/Flamsteed
stars		 12
Stars with planets 7
Stars brighter than 3.00m 0
Stars within 10.00 pc (32.62 ly) 0
Brightest star δ Crt (Labrum) (3.57m)
Nearest star LHS 2358
(34.86 ly, 10.69 pc)
Messier objects 0
Meteor showers Eta 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 raven 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, Delta Crateris the brightest star with a magnitude of 3.56.

Mythology

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

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. The constellations of Corvus the crow and Hydra the water-snake are also identified with this myth.[1]

Equivalents

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).[2]

In the Society Islands, Crater was recognized as a constellation called Moana-ohu-noa-ei-haa-moe-hara.[3]

Characteristics

Covering 282.4 square degrees and hence 0.685% of the sky, Crater ranks 53rd of the 88 constellations in area.[4] 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'.[5] 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°.[6] Its position in the Southern Celestial Hemisphere means that the whole constellation is visible to observers south of 65°N.[4][lower-alpha 1]

Features

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

Stars

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.[7] Within the constellation's borders, there are 33 stars brighter than or equal to apparent magnitude 6.5.[lower-alpha 2][4]

The three brightest stars—Delta, Alpha and Gamma Crateris—from a triangle nearby the brighter star Nu Hydrae in neighbouring Hydra.[9]

Traditionally called Alkes, Alpha Crateris is an orange-hued giant star of magnitude 4.1, 159 ± 2 light-years from Earth.[10] Its traditional name means "the cup". Beta Crateris is a blue-white hued star of magnitude 4.5, 266 light-years from Earth. Gamma Crateris is a double star divisible in small amateur telescopes. The primary is a white star of magnitude 4.1, 84 light-years from Earth. The secondary is of magnitude 9.6. Delta Crateris is the brightest star in Crater at magnitude 3.6. 186 ± 2 light-years away,[10] it is an orange-hued giant star.[11]

Located near Alkes is the red-hued R Crateris,[9] a semi-regular variable 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.

SZ Crateris is a magnitude 8.1 variable star. It is a nearby star system located about 44 light years from the Sun. It is also identified as Gliese 425, and in the past it was known as Abt's Star.

Deep-sky objects

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.[12]

Namesakes

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

See also

Notes

  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.[4]
  2. ↑ Objects of magnitude 6.5 are among the faintest visible to the unaided eye in suburban-rural transition night skies.[8]

References

  1. ↑ Ridpath & Tirion 2001, p. 128.
  2. ↑ (Chinese)AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 5 月 31 日
  3. ↑ Makemson 1941, p. 282.
  4. 1 2 3 4 Ian Ridpath. "Constellations: Andromeda–Indus". Star Tales. self-published. Retrieved 2 December 2016.
  5. ↑ Russell, Henry Norris (1922). "The New International Symbols for the Constellations". Popular Astronomy. 30: 469. Bibcode:1922PA.....30..469R.
  6. ↑ "Crater, Constellation Boundary". The Constellations. International Astronomical Union. Retrieved 2 December 2016.
  7. ↑ 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. 121–23, 390–92, 506–07. ISBN 978-0-939923-78-6.
  8. ↑ Bortle, John E. (February 2001). "The Bortle Dark-Sky Scale". Sky & Telescope. Sky Publishing Corporation. Retrieved 6 June 2015.
  9. 1 2 Arnold, H.J.P; Doherty, Paul; Moore, Patrick (1999). The Photographic Atlas of the Stars. Boca Raton, Florida: CRC Press. p. 140. ISBN 978-0-7503-0654-6.
  10. 1 2 van Leeuwen, F. (2007). "Validation of the New Hipparcos Reduction". Astronomy and Astrophysics. 474 (2): 653–64. arXiv:0708.1752Freely accessible. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357.
  11. ↑ Ridpath & Tirion 2001, pp. 130-131.
  12. ↑ Nola Taylor Redd (March 5, 2014). "Monster Black Hole Spins at Half the Speed of Light". Space.com. Retrieved March 5, 2014.
  • 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.
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