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Cancer the Crab Constellation - Stars, Facts, Myths - Zodiac Series
The Constellation Cancer
Many of the major constellations in the sky have a legend or two attached to them.
The constellations of the zodiac are twelve in number.
This hub will focus on the constellation Cancer or The Crab.
Many of the constellations that we know today had Greek names proposed by Ptolemy in A.D. 140. Scientists still use the names for the most part, but many were translated to Latin.
Legend has it that the constellation Cancer represents a crab that was supposed to rescue a monster with numerous heads named Hydra. Hydra was in a battle with Hercules, who immediately killed the crab.
Juno, the Queen of Olympus, originally sent the crab to kill Hercules. To recognize its sacrifice, Juno asked the god Jupiter to send it to the heavens where all could see it forever.
Within Cancer, the star cluster Praesepe (pronounced prē-sē’-pe) also has some legends and history attached to it. Praesepe is also known as the “Bee Hive.” In ancient times, the star cluster became a weather guide. If, on a clear night you couldn’t see this particular star cluster, a large, violent storm was about to happen.
On either side of the star cluster are two other stars: δ Cancri and γ Cancri - these are their Greek names. The first one is also called “Asellus Australis" and the second is “Asellus Borealis,” - their Latin names.
Legend tells the story of two asses, and how they got their names. The Greek god, Bacchus, happened upon a marsh that was almost impassable. He saw the two asses, mounted one and continued on his way to the Temple of Jove. He was so grateful for their help, he elevated both of them to the heavens. Now, Asellus Borealis is the Northern Ass and Asellus Australis is the Southern Ass.
Praesepe is known as The Manger. Now, δ Cancri and γ Cancri “feed at the manger.”
The Chinese had their own name for the Praesepe cluster: The Exhalation of Piled-Up Corpses, for reasons unknown.
Did You Know the Mythological History of Cancer?
Cancer Constellation Facts
Space is a very interesting place, and it beholds so many facts and mysteries - it's like uncovering intricate puzzle pieces.
In the sky, Cancer is located between the constellation Gemini to the east and Leo to the west. It’s also right above another constellation, Hydra.
Cancer is more difficult to find in the sky because its stars are not very bright, as seen from Earth. Most lie in the 4th or 5th magnitude, meaning that if “O” is brightest and “5” is not very bright, then they won't register as very bright to the naked eye.
Cancer is located between a triangle of stars created by nearby constellations. Pollux (in Gemini) lies to its east, Procyon (Canis Minor) to the south and Regulus (in Leo) to the west. (see photo)
The constellation itself makes an almost upside-down Y-pattern, with β Cancri and α Cancri toward the south, δ Cancri in the middle, γ Cancri in the upper middle part, and ι Cancri to the north.
β Cancri is just northeast of Procyon, Canis Minor's bright star.
α Cancri is also named Acubens. It’s a double star. It lies a few degrees west of β Cancri, and closer to Regulus.
γ Cancri is interesting because the moon often passes in front of it, blocking it from view. This is called “occultation.”
All these are the Greek names for the prominent stars in the constellation. I use them here, because in star charts, these are the names that you often see. See the table below for a listing of their Latin names.
Acubens (also means "claws")
More Constellation Information
The Bee Hive
Cancer is notable for its two clusters: M44 and M67. The “M” stands for messier objects.
M44 is also known as Praesepe. You can actually see it without the use of binoculars of a telescope.
Four stars make an imaginary square around it: γ, δ, η and θ Cancri.
Mentioned above, this cluster has a third name, "The Bee Hive." It looks almost like a nebula to the naked eye. Some have mistaken it for a comet. Galileo was the first astronomer to study the cluster when he sighted it with his telescope.
The Bee Hive contains 358 stars. At least 20 of them are ten times brighter than the sun. 80 of those stars are brighter than a magnitude of 10. Many are less bright, as dim as the 18th magnitude.
Praesepe is 500 light years away and is 30 light years across.
The Cluster M67
The other cluster, M67 is over 2,500 light years away. It has about 1,000 stars attributed to it. Though you can see it with the naked eye, it's definitely more difficult than with binoculars or a telescope. Most of the stars bear a magnitude between 9 and 12.5.
Cancer is also interesting in that in June of 1895, all the planets in our solar system, except Neptune, could be found in this constellation in the sky. Halley’s Comet also made an appearance in the constellation in 1531.