An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

The Crab. The dimmest → constellation of the → Zodiac, located in the northern hemisphere at approximately R.A. 8 h and Dec. +20°. The main feature of the constellation is the open cluster → Praesepe (M 44). Abbreviation: Cnc; genitive form: Cancri.

Cancer,from L., from Gk. karkinos; PIE base *qarq- "to be hard" (like the shell of a crab); cf. Skt. karkatah "crab," karkarah "hard."
In Gk. mythology the Crab was sent by the goddess Hera to bite Hercules in the midst of the struggle with → Hydra, but Hercules crushed the crustacean with his heel. Hera rewarded the Crab by placing it in the → Zodiac.

Xarcang "crab," from Mid.Pers. karcang, cf. Lori qerženg from kar-, qer- + cang, ženg "claw." The component xar/qer may be related to Av. xruta-, xraoždva- "hard," as in xruždisma- "hard ground" (from xruždi- + zam-), and to the PIE *qarq- "to be hard." In that case, the Pers. term for crab would literally mean "hard claw."

→ Tropic of Cancer.

A parallel of latitude on the Earth, 23°26' north of the equator, where the Sun is directly overhead on the northern → summer solstice (around the 21st June each year), because the Sun reaches its most northerly declination. Some 3,000 years ago, this occurred when the Sun was in the → Zodiac constellation → Cancer, hence the name. However, → precession has resulted in a shift of the position of the Sun so that it is now in the constellation → Gemini on the summer solstice.

→ tropic; → Cancer.