Cancer | Constellation

Cancer-constellation-map

Cancer is one of the twelve constellations of the zodiac. Its name is Latin for crab and it is commonly represented as one. Its astrological symbol is Cancer.svg (Unicode ?). Cancer is a medium-size constellation with an area of 506 square degrees and its stars are rather faint, its brightest star Beta Cancri having an apparent magnitude of 3.5. It contains two stars with known planets, including 55 Cancri, which has five: one super-earth and four gas giants, one of which is in the habitable zone and as such has expected temperatures similar to Earth. Located at the center of the constellation is Praesepe (Messier 44), one of the closest open clusters to Earth and a popular target for amateur astronomers.

Characteristics
Cancer is a medium-sized constellation that is bordered by Gemini to the west, Lynx to the north, Leo Minor to the northeast, Leo to the east, Hydra to the south, and Canis Minor to the southwest. The three-letter abbreviation for the constellation, as adopted by the International Astronomical Union in 1922, is ‘Cnc’. The official constellation boundaries, as set by Eugene Delporte in 1930, are defined by a polygon of 10 sides (illustrated in infobox). In the equatorial coordinate system, the right ascension coordinates of these borders lie between 07h 55m 19.7973s and 09h 22m 35.0364s, while the declination coordinates are between 33.1415138

Stars
See also: List of stars in Cancer
Cancer is the dimmest of the zodiacal constellations, having only two stars above the fourth magnitude. The German cartographer Johann Bayer used the Greek letters Alpha through Omega to label the most prominent stars in the constellation, followed by the letters A, then lowercase b, c and d.

The constellation Cancer as it can be seen by the naked eye. AlltheSky.com
Also known as Altarf, Beta Cancri is the brightest star in Cancer at apparent magnitude 3.5 and located 290 light-years from Earth. It is a binary star system, its main component an orange giant of spectral type K4III that is varies slightly from a baseline magnitude of 3.53?dipping by 0.005 magnitude over a period of 6 days. An aging star, it has expanded to around 50 times the Sun’s diameter and shines with 660 times its luminosity. It has a faint magnitude 14 red dwarf companion located 29 seconds away that takes 76,000 years to complete an orbit. Altarf represents a part of Cancer’s body.

Athanasius Kircher said that in Coptic Egypt it was Klaria, the Bestia seu Statio Typhonis (the Power of Darkness). Jerome Lalande identified this with Anubis, one of the Egyptian divinities commonly associated with Sirius.

In most Germanic and Slavic languages, the constellation is known as “The Crayfish”.

Mythology
Heracles attacked by Karkinos (bottom) and the Lernaean Hydra, under the aid of Athena. White-ground Ancient Greek Attic lekythos, ca. 500?475 BC. Louvre Museum, Paris.
The creation of the constellation is explained in Greek mythology by the short-lived association of the crab Karkinos with one of the Twelve Labors of Heracles, in which Heracles battled the multi-headed Lernaean Hydra. Hera had sent Karkinos to distract Heracles and put him at a disadvantage during the battle, but Heracles quickly dispatched the crab by kicking it with such force that it was propelled into the sky. Other accounts had Karkinos grabbing onto Heracles’s toe with its claws, but Heracles simply crushed the crab under his foot. Hera, grateful for Karkinos’s effort, gave it a place in the sky.[1] Some scholars have suggested that Karkinos was a late addition to the myth of Heracles in order to make the Twelve Labors correspond to the twelve signs of the Zodiac.[17]

Athanasius Kircher said that in Coptic Egypt it was Klaria, the Bestia seu Statio Typhonis (the Power of Darkness). Jerome Lalande identified this with Anubis, one of the Egyptian divinities commonly associated with Sirius.

In most Germanic and Slavic languages, the constellation is known as “The Crayfish”.

Mythology
Heracles attacked by Karkinos (bottom) and the Lernaean Hydra, under the aid of Athena. White-ground Ancient Greek Attic lekythos, ca. 500?475 BC. Louvre Museum, Paris.
The creation of the constellation is explained in Greek mythology by the short-lived association of the crab Karkinos with one of the Twelve Labors of Heracles, in which Heracles battled the multi-headed Lernaean Hydra. Hera had sent Karkinos to distract Heracles and put him at a disadvantage during the battle, but Heracles quickly dispatched the crab by kicking it with such force that it was propelled into the sky. Other accounts had Karkinos grabbing onto Heracles’s toe with its claws, but Heracles simply crushed the crab under his foot. Hera, grateful for Karkinos’s effort, gave it a place in the sky. Some scholars have suggested that Karkinos was a late addition to the myth of Heracles in order to make the Twelve Labors correspond to the twelve signs of the Zodiac.

Astrology
Main article: Cancer (astrology)
As of 2002, the Sun appears in the constellation Cancer from July 21 to August 9. In tropical astrology, the Sun is considered to be in the sign Cancer from June 21 to July 22, and in sidereal astrology, from July 16 to August 15.

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