Cancer

Cancer is a moderately sized constellation visible in the northern sky around February, and one of the twelve members of the zodiac.

Despite this, it is not particularly conspicuous. Its brightest star has a magnitude of only 3.5.

It is best known for its deep sky objects, and in particular the open cluster M44, the Beehive cluster or Praesepe. This can be found near the center of the constellation.

Cancer is Latin for ‘crab’ and is identified with a rather inconsequential event in Greek mythology. Hercules, Zeus’ son, was given 12 labors by Hera, Zeus’ wife, which would each test his strength and courage. Hera hoped these 12 labors would prove to Zeus that Hercules was unworthy of his love. The second of these 12 labors was to kill the Lernean Hydra, which had a long snake or dragon-like body and nine heads. If anyone succeeded in cutting off one of its heads, it would grow another one in its place. In order to make sure that Hercules failed at this task (Hera was very jealous of Zeus’ love for Hercules), Hera sent a large crab to grab Hercules by the heel and distract him while he was fighting the Hydra. During the fight with the Hydra, Hercules, who took his nephew Iolas along, would cut off one of the Hydra’s heads and Iolas would sear that neck with a torch so that no new head could grow back. Fearing that Hercules might indeed defeat the Hydra, Hera sent in the crab to grab Hercules’ foot. However, as the crab grabbed his foot, Hercules stomped down with his other foot and crushed the crab. He then cut the final head of the Hydra off and Iolas seared it, thus defeating the Hydra, and Hera. To honor Hercules’ great victory and to remind Hera of her failure, Zeus placed the constellation of Cancer the Crab in the sky.

The constellation gives its name to the Tropic of Cancer, the line at a latitude of 23.5°N where the Sun is overhead at the June solstice. In ancient times the Sun lay in the constellation at the time of the solstice, though this is no longer the case. The precession of the equinoxes means the Sun now lies in Taurus on June 21.

Being a Zodiac constellation, Cancer has its own unicode emoji ♋

Cancer contains:

• Stars
  • β-Cnc (mag 3.5)
  • Asellus Australis (mag 3.9)
  • ι-Cnc (mag 4.0)
  • Acubens (mag 4.3)
  • Asellus Borealis (mag 4.7)
  • HD 71115 (mag 5.1)
  • χ-Cnc (mag 5.1)
  • 8-Cnc (mag 5.1)
  • ξ-Cnc (mag 5.2)
  • κ-Cnc (mag 5.2)
  • O¹-Cnc (mag 5.2)
  • σ³-Cnc (mag 5.2)
  • ρ²-Cnc (mag 5.2)
  • ζ²-Cnc (mag 5.3)
  • μ-Cnc (mag 5.3)
  • η-Cnc (mag 5.3)
  • θ-Cnc (mag 5.4)
  • π-Cnc (mag 5.4)
  • τ-Cnc (mag 5.4)
  • σ²-Cnc (mag 5.4)
  • ν-Cnc (mag 5.4)
  • 60-Cnc (mag 5.5)
  • φ¹-Cnc (mag 5.6)
  • BP Cnc (mag 5.6)
  • 3-Cnc (mag 5.6)
• Open Clusters
  • Messier 44 (mag 3.1)
  • Messier 67 (mag 6.9)
• Globular Clusters
  None
• Galaxy
  • • NGC 2775 (mag 10.3)
    • NGC 2672 (mag 11.6)
    • NGC 2648 (mag 11.8)
    • NGC 2749 (mag 12.0)
    • NGC 2608 (mag 12.1)
    • NGC 2563 (mag 12.4)
    • NGC 2545 (mag 12.4)
    • NGC 2535 (mag 12.6)
    • NGC 2764 (mag 12.7)
    • NGC 2750 (mag 12.7)
    • NGC 2619 (mag 12.7)
    • NGC 2562 (mag 12.9)
    • NGC 2673 (mag 12.9)
    • NGC 2789 (mag 13.1)
    • NGC 2623 (mag 13.4)
    • NGC 2744 (mag 13.4)
    • NGC 2599 (mag 13.4)
    • NGC 2554 (mag 13.5)
    • NGC 2592 (mag 13.6)
    • IC 2446 (mag 13.6)
    • NGC 2598 (mag 13.7)
    • NGC 2513 (mag 13.7)
    • NGC 2730 (mag 13.7)
    • NGC 2738 (mag 13.8)
    • NGC 2577 (mag 13.8)