It’s amazing how a small crab with a walk-on role in Greek mythology is such a fixture in our daily life today…
The constellation Cancer (Latin for crab) is one of the most modest in the sky. It has no particularly bright stars, and its only claim to fame is that it belongs to the zodiac, and contains the beautiful M44 open cluster — The Beehive. But back 2000-odd years ago it was a different story.
When the Sun reached its summer solstice (its most Northern position in the sky), the constellation it happened to be in front of was none other than Cancer. It was a big deal… For Mesopotamians, it marked the gateway for the descent of souls into incarnation.
That positioning of Cancer also gave rise to what we know today to be the Tropic of Cancer — the imaginary line we draw to depict latitude, also known as the Northern Tropic.
Even though, as a result of precession, the Sun’s most northerly position has now moved westwards between Gemini and Taurus, the name has stuck.But how did such a tiny crab find its way up into the sky in the first place?
In Greek mythology, Hera, the wife of Zeus, vowed to kill Heracles — the son of a mortal woman, and sadly also the son of philandering Zeus. In a fit of jealous rage she made Heracles insane, and in his insanity he killed wife and children. Guilt-ridden, poor Heracles consulted the oracle of Delphi for advice on how he could make up for his actions. The penance it was determined would be set by Heracles own cousin, Eurystheus. And so Eurystheus set Heracles 12 impossible tasks to complete called the 12 Labors of Heracles — the second of which was to slay Hydra, a serpentine water monster.
Still full of jealousy, Hera sought to distract Heracles during his battle by sending a crab to nip on his toe. But the tiny crab was no match for Heracles who crushed it beneath his foot. While it may have been just a brief appearance for our crab, Hera rewarded him for his efforts by placing him among the stars and he’s been there ever since.