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Though not as prominent as some of the other winter constellations, Cancer (Latin for "crab") is still an interesting constellation.

It received its name for the crab that Hera (wife of the Greek Olympian god-king, Zeus) sent to harass Hercules during his battle with the many-headed monster, Hydra, one of his famous Twelve Labours.

Hercules was the demi-god son of Zeus from one of his many liaisons with mortal women, this time with a maiden named Alcmene. Zeus tricked Alcmene into laying with him by taking the form of her husband, Amphitryon, and the offspring of that union was Hercules. Needless to say, Hera was not a staunch supporter of Hercules throughout his life.

During his battle with the Hydra, Hera sent a large crab to distract him, hoping it would result in his death by the Hydra, or, at least, his failure in that particular contest. Two versions exist as to what happened next - the crab is said to have bitten Hercules in the ankle while he was battling the Hydra, and Hercules, greatly annoyed, either stepped on and crushed the crab, or kicked the crab so hard it was launched into the sky (where it now sits on the opposite side of the night sky). In the version where Hercules crushed the crab, Hera, as a reward for its gallant effort, and to spite Hercules, placed it in the night sky.

The ancient Babylonians viewed this constellation as either a crab or a snapping turtle, and is said to have associated it with death and with a passage to the underworld (perhaps the precursor to the Greek and Roman myths surrounding the underworld). The ancient Egyptians associated it with Scarabaeus - the Scarab beetle, a sacred emblem of immortality.

Cancer has very few bright stars, making it one of the dimmest and least recognized constellations in the night sky. The brightest star, Tarf (from the Arabic meaning "the eye") is an orange giant star 50 times the diameter of our sun, and 660 times as luminous. A binary star system, Tarf has a companion red dwarf star. The second brightest star Acubens (magnification +4.2) is also a multi-star system. Its Arabic name is Al Zubanah, meaning "the claws."

The constellation's next two stars of note have an interesting association. Delta Cancri is often referred to as Asellus Borealis (Latin for "the northern donkey”), while Gamma Cancri is labelled Asellus Australis (Latin for "the southern donkey"). This is in reference to the ancient Greek myth about the war between the Olympian gods and the Giants. At some point during one of the battles, the god Dionysus and some other gods rode into the fray on the back of donkeys. The Giants, knowing nothing of donkeys, fled the field when they heard the donkeys bray. As a reward for their on-field exploits, the gods placed the donkeys (or at least two of them) in the sky next to the star cluster Phatne ("the manager"). The ancient Romans pictured these two stars as two donkeys feeding at a manger. Interestingly, Delta Cancri has the distinction of having the longest of all known star names; in Arabic it was Arkushangarushashtu, meaning "southeast star in the crab".

Delta Cancri also marks the location of the famous Beehive Cluster (M44), an open star cluster, which, at 577 light years distance, is one of the nearest and most populated (more than 1,000 stars) open star clusters to Earth. It is also known as Praesepe, which in Latin means both "hive" and "manager". At magnitude +3.7, Praesepe is visible to the naked eye from a dark site as a small, nebulous object, but appears more distinct as a beautiful cluster of stars in binoculars and scopes.

This Week

Venus continues to shine brightly high in the southwest sky as darkness falls, setting now around 8:30 p.m. At a brilliant magnitude -4.1, there is no question as to why it is often referred to as our "evening star."

Jupiter joins Mars in the dawn sky this week, appearing low above the east-southeast horizon about 40 minutes before sunrise. You will need an unobstructed view of the horizon and, depending on sky conditions, might find binoculars helpful in locating Jupiter. Mars sits to the upper right of Jupiter, appearing in the pre-dawn sky above the east-southeast horizon well before Jupiter makes its appearance; Mars may well have faded from view by the time Jupiter clears the horizon.

The ruddy-coloured star Antares sits to the lower right of the Red Planet; compare their respective reddish hues. Mercury and Saturn are both too close to the Sun to be visible.

Until next time, clear skies.

Glenn K. Roberts lives in Stratford, P.E.I., and has been an avid amateur astronomer since he was a small child. He welcomes comments from readers, and anyone who would like to do so is encouraged to email him at glennkroberts@gmail.com.

Events:

Jan. 29 - Moon at apogee (farthest from Earth)

Feb. 2 - First quarter moon

More ATLANTIC SKIES