COSMOS / CONSTELLATIONS / CNC
Cancer (Crab)
The Crab. IAU abbreviation Cnc. One of the 48 classical constellations listed by Ptolemy in the Almagest in the 2nd century AD.
STAR CHART
KEY FACTS
- IAU abbreviation
- Cnc
- Latin name / genitive
- Cancer / Cancri
- Position
- Right ascension ≈ 8 h 37 m; declination +7° to +33°
- Visibility from Türkiye
- Visible in full from anywhere in Türkiye. When it crosses the meridian its centre stands about 70° above the horizon from Ankara.
- Best time to observe
- Best placed at 21:00 Türkiye time around 28 March.
- Number of stars
- 104 stars brighter than magnitude 6.5 in the catalogue; 6 brighter than 5 and 2 brighter than 4.
INTERACTIVE LAB
Where is Cancer tonight?
The lab opens for Ankara on today’s date. Drag the time slider through the night; the “Best night” button jumps to the date when the constellation is highest at 21:00 (around 28 March). Change the city to compare the view from elsewhere in Türkiye and around the world.
MYTH, HISTORY AND OBSERVING
The crab crushed by Heracles during his fight with the Hydra; it is the faintest constellation of the zodiac. At its centre the Beehive Cluster (M44, Praesepe) is visible to the naked eye as a hazy patch under dark skies; Galileo counted dozens of stars in it with his telescope. The older open cluster M67 is also here.
BRIGHTEST STARS
| Star | Magnitude | Distance (light-years) | Spectral type |
|---|---|---|---|
| Tarf | 3.53 | 303 | K4III |
| Asellus Australis | 3.94 | 131 | K0III |
| ι Cnc | 4.03 | 331 | G8Iab: |
| Acubens | 4.26 | 188 | A5m |
| Asellus Borealis | 4.66 | 181 | A1IV |
| Tegmine | 4.67 | 82 | G0V |
| χ Cnc | 5.13 | 60 | F6V |
| HIP 41325 | 5.13 | 395 | G8II |
Magnitude: apparent brightness; the smaller the number, the brighter the star. Distances derive from parallax measurements and are uncertain for distant stars. Source: HYG v4.1 star catalogue (CC BY-SA 4.0).
SOURCES
Position, visibility and best observing time were computed approximately for this page from the catalogue stars (Ankara, 39.9° N). The 88 constellations were adopted by the IAU in 1922; their boundaries were drawn by Eugène Delporte in 1930.