Constellation, Oct
Octans: the Octant
Octans covers 291 square degrees of sky, the 50th largest of the 88. Its brightest star is star HIP 107089. It is best placed in the evening sky in September.
Octans at a glance
| Fact | Value |
|---|---|
| IAU abbreviation | Oct |
| Meaning | the Octant |
| Pronounced | OCK-tanz |
| Genitive, used in star names | Octantis (for example a Bayer name such as α Octantis) |
| Area | 291 square degrees, number 50 of 88 by size |
| Stars to magnitude 6 in our catalogue | 35 |
| Brightest star | star HIP 107089, magnitude 3.7 |
| Best seen | Evenings in September, when it is highest at 9 pm |
| Declination range | -90° to -74° |
| Borders | Apus, Hydrus, Pavo, Mensa, Chamaeleon, Indus, Tucana |
Where on Earth you can see Octans
Octans spans declinations -90° to -74°. Every part of it rises above the horizon at some moment for observers between latitudes 90°S and 0°N. Some of it can be seen from latitudes 90°S to 16°N. South of 16°S 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 | Never rises | below the horizon |
| New York | 40.7°N | Never rises | below the horizon |
| London | 51.5°N | Never rises | below the horizon |
| Tromsø | 69.6°N | Never rises | below the horizon |
| Tokyo | 35.7°N | Never rises | below the horizon |
| Sydney | 33.9°S | Never sets | 40° |
Octans's named stars
These stars in Octans 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) |
|---|---|---|---|
| Polaris Australis | σ Octantis | 5.45 | 280 |
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 Octans'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