Cancer

The constellation of Cancer (abbreviation: Cnc) represents the Crab sent by Juno to save the Hydra in its battle with Hercules but unfortunately crushed underfoot during the ensuing melee. It is a dim northern constellation (shaped a bit like Orion) and the fourth sign of the zodiac, located between Castor and Pollux of Gemini and Regulus of Leo.

In former times the Sun used to lie in Cancer when it reached its point farthest north – the time of the summer solstice – but today, because of precession, the Sun passes through Cancer from late July to early August.

X Cancri is a semi-regular variable with a striking red color and an easy object with binoculars (magnitude range 5.6 to 7.5; period 195 days; RA 08h 55.4m, Dec +17° 14'). Cancer also contains the open clusters Praesepe (M44) and M67 (NGC 2682). The latter has contains several hundred stars and is best seen through larger telescopes (magnitude 6.9; diameter 30'; RA 08h 50.4m, Dec +11° 49'. See below for details of the constellation's brightest stars.

M67

M67 is an open cluster, containing more than 500 stars, which lies at a distance from the Sun of about 2,700 light-years. With an estimated age between 3.2 billion and 5 billion years is the oldest known open cluster in the solar neighborhood, although older ones are known at greater distances.

Stars in Cancer brighter than magnitude 4.0
star	vis mag	abs mag	spec type	distance (ly)	RA (h m s)	Dec (° ' ")
Beta (Altarf)	3.53	0.14	K4IIIBa0.5	290	08 16 31	+09 11 08
Delta (Asellus Australis)	3.94	0.83	K0III-IIIb	136	08 44 41	+18 09 15