Constellation, Cnc
Cancer: the Crab
Cancer covers 506 square degrees of sky, the 31st largest of the 88. Its brightest star is Tarf. It is best placed in the evening sky in March.
Cancer at a glance
| Fact | Value |
|---|---|
| IAU abbreviation | Cnc |
| Meaning | the Crab |
| Pronounced | CAN-ser |
| Genitive, used in star names | Cancri (for example a Bayer name such as α Cancri) |
| Area | 506 square degrees, number 31 of 88 by size |
| Stars to magnitude 6 in our catalogue | 49 |
| Brightest star | Tarf, magnitude 3.5 |
| Best seen | Evenings in March, when it is highest at 9 pm |
| Declination range | 7° to 33° |
| Borders | Gemini, Leo, Hydra, Lynx, Canis Minor, Leo Minor |
Where on Earth you can see Cancer
Cancer spans declinations 7° to 33°. Every part of it rises above the horizon at some moment for observers between latitudes 57°S and 90°N. Some of it can be seen from latitudes 83°S to 90°N. North of 83°N none of it ever sets. This is geometry only: it ignores haze, hills and buildings near the horizon.
From six cities
| City | Latitude | Visibility | Middle at its highest |
|---|---|---|---|
| Pune | 18.5°N | All of it rises | 88° |
| New York | 40.7°N | All of it rises | 69° |
| London | 51.5°N | All of it rises | 59° |
| Tromsø | 69.6°N | All of it rises | 40° |
| Tokyo | 35.7°N | All of it rises | 74° |
| Sydney | 33.9°S | All of it rises | 36° |
Cancer's named stars
These stars in Cancer have names approved by the IAU Working Group on Star Names. Magnitude is brightness: a lower number is brighter, and the faintest stars seen with the naked eye on a dark night are about magnitude 6.
| Star | Designation | Magnitude | Distance (light-years) |
|---|---|---|---|
| Tarf | β Cancri | 3.53 | 300 |
| Asellus Australis | δ Cancri | 3.94 | 130 |
| Acubens | α Cancri | 4.26 | 190 |
| Asellus Borealis | γ Cancri | 4.66 | 180 |
| Tegmine | ζ1 Cancri | 4.67 | 81.8 |
| Nahn | ξ Cancri | 5.16 | 370 |
| Piautos | λ Cancri | 5.92 | 460 |
| Copernicus | 55 Cancri | 5.96 | 40.2 |
Distances are about, from the HYG database (Hipparcos parallax), and "not known" means the catalogue has no reliable parallax for that star.
How these facts were found
The name, meaning and boundaries are the IAU's. Area, borders and the latitude ranges are computed from those boundaries; the brightest star and the star count come from a magnitude-6 star catalogue; star names are matched to the catalogue by Hipparcos number and checked by position. The month is when Cancer's middle crosses the north-south line of the sky at 9 pm local solar time. See How we know.
Sources
- IAU: The Constellations. Names, meanings, pronunciations and boundaries
- IAU Working Group on Star Names. The official names of stars
- astronomy-engine. The MIT licensed library that does the calculations, run on the page's build machine and in the app
- HYG database v4.4 (astronexus). Distances, spectral types and luminosities, licence CC BY-SA 4.0