Representation of a crab is the most common outcome of the studies of all ancient civilizations over formation of the Cancer Constellation. According to the Greek folklore in this regard, Zeus when fell in love with the Tiryns queen Alcmene, the child resulting out of their union was a son and was named Heracles (or Hercules), who later on turned out to be a hero for Greeks. This love and union resulted in the jealousy of Hera to the extent that she pledged to kill their son. After many futile attempts of killing Hercules, she introduced Cancer, a giant crab, while Hercules was busy fighting with a huge serpent Hydra, in water. By sending Cancer, Hera wanted to increase the power of Hydra. But after a brutal struggle, Hercules defeated both of them and crushed the crab's shell. In the praise of its loyalty, Hera acclaimed crab by drawing its image amongst the stars.
Locating the Cancer constellation is not as easy as it may seem and can be a tough feat. As you attempt to find the huge crab as signified theoretically, you may end up viewing the letter "Y" in reverse position. Therefore, some words of advice are a must before trying to locate Cancer constellation. Ideally, one should first try to locate the Big Dipper, which is part of the Ursa Major, and Leo. These two constellations are rather simple to identify. Finding the Big Dipper is easy because of it comprises of the seven stars and its location is in the North. Further locating gets sufficed with the help of roadmap to signify the crab in Cancer constellation. In fact, Cancer can be found between east of Gemini and west of Leo and locates between 6 to 33 degrees North. The best time to view this constellation from the Northern hemisphere is during January 13 to 17.
Cancer constellation, as such, does not comprise of any brightest stars but there isn't any beehive in it either, so much what it was referred to in the ancient times. "Beehive" is also known to be comprising of 300 stars being an open cluster. Famous scientist Galileo, after inventing his telescope, viewed the Beehive and studied that almost all the stars in this open cluster were about to finish their planetary lives. With regard to the chief stars of Cancer constellation, Al Tarf is known to be the brightest in it. In spite of being nearly 700 times brighter when compared to Sun, we see it quite faint because of its far distance from us. The size of Al Tarf can be judged based upon the fact that one star in its neighbourhood would take 76,000 Earth years to commence one full revolution of it. Furthermore, Al Tarf is such a star in the Cancer constellation that may look 30 times incandescent than our full moon, when observed from that revolving star.
A spiral galaxy identified as NGC2775, which is part of the Cancer constellation, is located at more than 60 M light years from us. Using a telescope, if you try seeing it and observe some light, you may conclude that the light must have started 60 million years back, from the galaxy.