Short Constellation Guide

The Crab (Cancer)

The constellation of the crab is small and difficult to see; many people cannot see any resemblance to a crab. It lies between the Twins (in the west) and the Lion (in the east). The crab is one of the most famous zodiac constellations, although it is the least sizeable among them. About 2500 years ago, the sun reached its most northerly position in the sky (called summer solstice) when it stood before this constellation. At this time, around the 21st of June, the sun reaches its zenith for an earthly observer at 23.5° north latitude at noon – that means it will be directly over the observer. This geographical latitude represents the northern boundary of the tropics, and is called the “tropic of Cancer”. (Today, due to planetary precession shift, the most northerly position of the sun actually lies in the Bull constellation. In this way, we can imagine that the tropic of Cancer would be called the Tropic of Taurus if we were just naming this region today.

From mythology – an interesting story that has been told for many centuries

In the Greek sagas, Cancer was the crab who was sent to distract Hercules during his battle against the monster Hydra. Hercules, however, could crunch him underfoot. As reward for his sacrifice, Hera (Zeus’ wife) set the crab among the stars.

Finding the constellation in the sky

The dim constellation Cancer lies in the middle of a triangle formed by three points: Pollux in the Twins (Gemini), Regulus in the Lion (Leo) und Procyon in Canis Minor („smaller dog“ constellation). In the middle of Cancer, the pale star cluster Praesepe (“crib,” also called “The Beehive Cluster”).