Cancer, or the
Crab, is one of the twelve constellations of the
zodiac family. It lies north of the
celestial equator and is somewhat difficult to locate, as its stars are a bit faint.
More than 2,000 years ago, the Sun used to lie in Cancer when it reached its furthest point to the north, during the time of the
summer solstice of the Northern Hemisphere. Because of this, it's been seen as one of the four
cardinal signs that mark the beginning of the seasons. Today, though, the Sun now lies within
Gemini during this time of year because of precession.
The constellation has been recognized as a crab in many ancient cultures such as the Syrians, Hebrews, Arabs, and Turks. In
Greek mythology, it's said to represent the crab that attacks Hercules (or Heracles) during his fight with
Hydra, a water snake with nine heads. While the two fought, Hydra called upon the crab who pinches
Hercules' foot. Hercules kills the crab and the hydra, but the crab is rewarded, some say by Hera, by its placement in the sky.
The
Chaldeans saw the constellation as a portal the souls passed through before taking human form called the
Gate of Men, while ancient Babylonian texts refer to the constellation as a tortoise. To the Egyptians, it was seen as a
scarab.
Within Cancer are two well known
open star clusters, M44 and M67. M44 is more commonly known as
Praesepe, the Latin word for "manger", or the
Beehive Cluster. The cluster contains up to a hundred or more stars and is visible to the naked eye, but best viewed with binoculars or a small telescope. It appears as a misty cloud or patch to the naked eye and has been seen in many old texts and literature.
Such names as "
Little Mist," "Little Cloud," and "Cloudy Star" have been given to this cluster, and it's been mentioned by
Ptolemy as "The Nebulous Mass in the Breast (of Cancer)". It also appears in
Johann Bayer's star chart as
Nubilum, or Cloudy Object. It's also been used as a weather indicator in ancient times, said to forecast approaching storms.
Two of the most visible stars, Gamma Cancri or
Asellus Borealis (Northern Donkey) and
Delta Cancri or
Asellus Australis (Southern Donkey) were seen by
Eratosthenes as the two donkeys the gods Dionysos and Silenus rode during the battle against the Titans.
The other star cluster,
M67, is one of the oldest known open star clusters, dated at nearly 10 billion years. It's composed of over 100 stars and is best viewed with a larger telescope.