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Information on Cancer the Constellation

Cancer is one of the 88 recognized constellations, or groupings of stars, and dates back to ancient times. Cancer is a faint and hard-to-identify constellation even for those people who regularly view the stars. Cancer is one of the 12 Zodiac constellations and lies along the apparent path the Sun traces across the sky during the year---a path known as the ecliptic.
  1. Locating Cancer

    • Five dim stars make up Cancer, which although it represents a crab, looks more like an upside-down letter "Y." To locate Cancer, an observer should first find the two constellations on either side. Leo the Lion is to the west of Cancer and actually does look like a lion lying down, with a large backwards question mark as its head and shoulders. Gemini the Twins, to the east of Cancer, contains two bright stars side by side, called Castor and Pollux. The region of space between these two constellations contains Cancer. The faint constellation called Lynx is north of Cancer, while Canis Minor, a small constellation containing a very bright star named Procyon, is to Cancer's south.

    Ancient legend

    • The ancient myth regarding Cancer involves the second labor of the mighty Hercules. As Hercules fought with the many-headed hydra in a swamp, the goddess Hera, who hated Hercules, enlisted a giant crab to sneak up on the hero. The crab did so and grabbed Hercules by the heel but was no match for him. Hercules rapidly dispatched it, and Hera placed the crab in the sky in the form of a constellation--a faint one since it could not complete its mission to destroy Hercules.

    Al Tarf

    • The brightest star in Cancer is Al Tarf and astronomers affix the name beta Cancri to it. Although it appears quite dim from Earth, this is because it is nearly 300 light years away, meaning that he light that reaches an individual's eyes from this star started the journey across space almost 300 years ago. In reality, Al Tarf is 660 times more luminous than the Sun. A high-powered telescope reveals that Al Tarf is a double star, with a companion star orbiting it. It takes around 76,000 years for the companion to finish one entire circle around Al Tarf.

    M44

    • Easily Cancer's most interesting feature to astronomers is a star cluster called the Beehive, also known as the Praesepe. Galileo was the first individual to use a telescope to look closely at this bunch of stars. It looks like a hazy cloud of light to an unaided eye and the ancient sky observers, although they had no idea what comprised it, knew the Beehive Cluster well. It is 580 light years from Earth and has a diameter of some 16 light years. Galileo's primitive telescope allowed him to count around 40 separate stars in this cluster, and the largest telescopes available today can find about 200. The French astronomer Charles Messier, who cataloged "deep sky objects," added the Praesepe to his list on March 4, 1769, as Messier object 44, or M44.

    Delta cancrids

    • One minor shower of meteors, also called shooting stars, radiates from the constellation during the middle of every January. The Delta Cancrids seem to come from the Beehaive Cluster at a mundane rate of just four an hour. The storm is at its peak on January 16, and the meteors typically are very fast movers. These small bits of rock and debris enter the Earth's atmosphere and burn up as the friction with the air ignites them.


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