Cancer represents the crab that, in Greek mythology, was crushed underfoot by Hercules during his battle with the multiheaded Hydra. It lies between Gemini and Leo and is the faintest constellation of the Zodiac; its brightest star, Beta Cancri, is of magnitude 3.5. The Sun is within Cancer's boundaries from July 20th until August 10th.
Points of Interest
A multiple star. Through a small telescope, it is seen to consist of two stars, of magnitude 5.1 and 6.2. A telescope with an aperture larger than about 6 in (150 mm) will show that the brighter component has a much closer companion, of magnitude 6.1, which orbits it every 60 years.
An open cluster, also known as the Beehive cluster or the Manger. (Praesepe is Latin, meaning both manger and hive) It appears as a cloudy patch at the limit of naked-eye visibility - its brightest are of 6th magnitude, and it was known to the ancient Greeks - but binoculars show it as a field of stars more than three times the apparent width of the full Moon. It lies about 520 light-years away. To the north and south of the cluster are the stars Gamma Cancri (magnitude 4.7) and Delta Cancri (magnitude 3.9). In ancient times, these were visualized as donkeys feeding at the manger, hence they are known as the aselli, or asses.
M67 (Open Cluster)
An open cluster. It contains more stars than M44 (Praesepe), but it is farther away from us (about 2,600 light-years) and so appears fainter and smaller.