The Mythology Behind The Cancer Constellation Explained

Cancer, one of the 13 Zodiac constellations (that's right, there are 13 now according to new research), is a dim upside-down Y often considered to resemble a giant crab lurking in the night sky (via Space). One of its stars, Acubens, translates to "the claw." Cancer, the Latin word for crab, does not represent just any scuttling sea creature, but rather a monster from Greek mythology that went toe-to-toe – or rather, claw-to-claw – with Hercules himself.

Hercules had to suffer 12 "labors" as punishment for killing his family. The second of those labors was not to do battle with a crab but rather the water serpent, Hydra. However, the goddess Hera, enraged and jealous, sent Cancer to fight alongside Hydra to make the fight even more difficult for the demigod. Her attempts to thwart Hercules were in vain, as Hercules was able to defeat Cancer before killing the Hydra with his club. 

There are a few different accounts of the crab's fate in the Hercules tale. According to Constellation Guide, Hercules was already fighting the multi-headed, poison-breathing Hydra — itself represented in a constellation — when Hera sent the giant crab as a distraction. One telling claims that Hercules kicked Cancer into the sky once it approached, and in another, the crab was simply crushed by the Greek hero. 

The latter telling has Hera place Cancer's body in the night sky as a reward for its efforts in stopping Hercules. However, since the giant crab was so easily defeated by Hercules, Hera wanted to make sure it wasn't too impressive of a reward, so she put Cancer in a dim part of the sky so it would struggle to be seen. That's why the Cancer constellation is the least bright out of all of its Zodiac brethren. Unsurprisingly, in the Zodiac calendar, Cancer is considered a water sign.