Constellation, Gem
Gemini: the Twins
Gemini covers 514 square degrees of sky, the 30th largest of the 88. Its brightest star is Pollux. It is best placed in the evening sky in February.
Gemini at a glance
| Fact | Value |
|---|---|
| IAU abbreviation | Gem |
| Meaning | the Twins |
| Pronounced | JEM-uh-nye, JEM-uh-nee |
| Genitive, used in star names | Geminorum (for example a Bayer name such as α Geminorum) |
| Area | 514 square degrees, number 30 of 88 by size |
| Stars to magnitude 6 in our catalogue | 73 |
| Brightest star | Pollux, magnitude 1.2 |
| Best seen | Evenings in February, when it is highest at 9 pm |
| Declination range | 10° to 35° |
| Borders | Auriga, Cancer, Orion, Canis Minor, Monoceros, Lynx, Taurus |
Where on Earth you can see Gemini
Gemini spans declinations 10° to 35°. Every part of it rises above the horizon at some moment for observers between latitudes 55°S and 90°N. Some of it can be seen from latitudes 80°S to 90°N. North of 80°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 | 84° |
| New York | 40.7°N | All of it rises | 73° |
| London | 51.5°N | All of it rises | 63° |
| Tromsø | 69.6°N | All of it rises | 44° |
| Tokyo | 35.7°N | All of it rises | 78° |
| Sydney | 33.9°S | All of it rises | 32° |
Gemini's named stars
These stars in Gemini 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) |
|---|---|---|---|
| Pollux | β Geminorum | 1.16 | 33.8 |
| Castor | α Geminorum | 1.58 | 50.9 |
| Alhena | γ Geminorum | 1.93 | 110 |
| Tejat | μ Geminorum | 2.87 | 230 |
| Mebsuta | ε Geminorum | 3.06 | 840 |
| Propus | η Geminorum | 3.31 | 380 |
| Alzirr | ξ Geminorum | 3.35 | 58.7 |
| Wasat | δ Geminorum | 3.50 | 60.5 |
| Mekbuda | ζ Geminorum | 4.01 | 1,400 |
| Jishui | ο Geminorum | 4.89 | 170 |
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 Gemini'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