|Area||282 sq. deg. (53rd)|
|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)|
|Meteor showers||Eta Craterids|
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.
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. 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. 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.
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.
In other cultures
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). 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. In the Society Islands, Crater was recognized as a constellation called Moana-ohu-noa-ei-haa-moe-hara.
Covering 282.4 square degrees and hence 0.685% of the sky, Crater ranks 53rd of the 88 constellations in area. 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'. 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°. Its position in the Southern Celestial Hemisphere means that the whole constellation is visible to observers south of 65°N.[a]
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. The three brightest stars—Delta, Alpha and Gamma Crateris—from a triangle nearby the brighter star Nu Hydrae in Hydra. Within the constellation's borders, there are 33 stars brighter than or equal to apparent magnitude 6.5.[b]
Delta Crateris is the brightest star in Crater at magnitude 3.6. 186 ± 2 light-years away. 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. Traditionally called Alkes "the cup", Alpha Crateris is an orange-hued star of magnitude 4.1, 159 ± 2 light-years from Earth. 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, shining with 69 times its luminosity.and a surface temperature of 4645 K.
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, 340 ± 20 light-years from Earth. The Hubble Space Telescope was unable to make out the two stars as separate objects. Gamma Crateris is a double star divisible in small amateur telescopes. The primary is a white main sequence star of spectral type A7V that is an estimated 1.81 times as massive as the Sun, while the secondary—of magnitude 9.6—has 75% the Sun's mass, and is likely an orange dwarf.
SZ Crateris is a magnitude 8.5 BY Draconis type 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.
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 98649 is a sunlike star with a planet in an eccentric orbit.
BD-10°3166 is a metallic orange main sequence star that was found to have a planet.
DENIS-P J1058.7-1548 is a brown dwarf.
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.
- 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.
- Objects of magnitude 6.5 are among the faintest visible to the unaided eye in suburban-rural transition night skies.
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- 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.
- Ridpath & Tirion 2001, p. 128.
- (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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|Wikimedia Commons has media related to:|
- The Deep Photographic Guide to the Constellations: Crater
- Warburg Institute Iconographic Database (over 150 medieval and early modern images of Crater)
- The clickable Crater