Cancer, la constelacion




Дата канвертавання24.04.2016
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CANCER, LA CONSTELACION

por Carlos Andrés Carvajal T.

Tomado de http://almaak.tripod.com/temas/constelaciones/cancer.html
El Cangrejo
Abreviación: Cnc

Forma Posesiva: Cancri

Ascensión Recta: 08.69 horas

Declinación: 20.15°


Es la constelación mas pequeña del zodiaco y ninguna de sus estrellas tiene una magnitud mayor a 4. Se encuentra rodeada por estrellas importantes como Régulus, Procyon, Castor y Pólux.
Mitología
Es el cangrejo que Hera mandó como aliado de la Hidra de Lerna cuando Hércules combatía contra ella en su segundo trabajo. Muerde al héroe en el pie desde las aguas de la laguna pero aquel lo pisa y lo aplasta sin que le afecte demasiado. Hera lleva al cangrejo al firmamento y lo coloca entre las constelaciones para recompensar su cooperación.
Objetos de Interés
M44 - NGC 2632. AR: 08h 40m 06.0s Dec: +19°59'00" (Época 2000). También llamado cúmulo Praesepe, Pesebre o Colmena, se extiende por un área mayor a la de la Luna y es uno de los cúmulos mas espectaculares del cielo. Se puede observar a simple vista pero con unos binoculares o un telescopio pequeño se pueden separar sus estrellas componentes. Se encuentra a 520 años luz del sol.

Al oeste de M44 se encuentra Zeta Cnc una estrella triple. Iota Cnc es una doble verde y naranja, ligeramente al noroeste se encuentra Iota2 Cnc una triple.



M67 - NGC 2682. AR: 08h 50m 24.0s Dec: +11°49'00" (Época 2000). 2º al oeste de Acubens (alfa Cnc) encontramos este cúmulo abierto de al menos 200 estrellas, dentro de ellas se destacan una de color anaranjado y otra de rojo intenso.
Tomado de http://www.astrofilitrentini.it/mat/costell/cnc_e.html
Major
stars
No star of the constellation exceeds the magnitude 3,5.
Description Constellation of the zodiac, through which the Sun transits from the end of July to the beginning of August. In past times the Sun was in Cancer when it was at the maximum north distance from equator (at the summer solstice, on June 21). Today, because of the precession of the equinoxes, the summer solstice is in the near constellation of Gemini; nevertheless the latitude at which the Sun appears to zenith on June 21 is still called Tropic of Cancer.

Cancer is the least bright of all the zodiacal constellations: none of its stars exceeds the fourth magnitude.

Near the center of the constellation there is M44, an open cluster called Praesepe or Beehive: it is constituted by at least 75 stars, all inferior to the sixth magnitude. It is accompanied by two stars which represent two little ass feeding at the manger ("praesepe", exactly): gamma Cancri (Asellus Borealis) and delta Cancri (Asellus Australis).

Mythology
and history
The constellation represents the crab which pricked Hercules' foot while the hero was struggling against Hydra that lived in the Lerna swamp. The hero crushed it with his heel, but the goddess Hera, hostile to Hercules, reserved him a little place in the sky.
Tomado de http://www.stargazers.iinet.net.au/cancer.htm
Cancer the Crab is the faintest of the Zodiac constellations, but it once had a position of importance in the sky.  During the time of ancient Greece the Sun reached it's most northerly position in the sky in Cancer, and this is why the Tropic of Cancer was named so (In the present day the sun now reaches the solstice point near the star eta () Geminorum.)  To find Cancer in the sky look between Gemini and Leo, although you may need a dark sky to see all it's stars. 

According to Greek mythology Cancer was the crab sent by Hera to distract Hercules as he fought the Hydra in the marshes at Lerna.  Hercules trod on it during the course of the long battle, whence Hera placed it amongst the stars for it's service.



Alpha () Cancri is also known as Acubens, which means claw.  It marks one of the large front claws that are common on crabs; the opposite claw is marked by iota Cancri but it has no other name.

Gamma () and delta () Cancri are known as Asellus borealis and Asellus australis respectively.  Their names mean the Northern Donkey and the Southern Donkey, and they are eating from the large open star cluster called Praesaepe, which means "the Manger."  Some stories say they are the donkeys in the stable when Jesus was born, other stories say they were two donkey's that helped the Titans during the war with Zeus and his siblings in Greek mythology.  Praesaepe is little used now, the common name of the Beehive is becoming popular instead.  If one looks carefully through large binoculars or a small telescope you may be able to make out the pyramid-like beehive with a few bees buzzing around it


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