Gemini
Gem · genitive Geminorum · northern sky
At a glance
- Catalogued stars
- 119
- Visible to the eye
- 119 stars
- Brightest star
- Pollux (1.14)
- Best seen
- January
- Declination span
- +12.9° to +31.9°
- Nearest star
- Pollux · 33.8 ly
Visible from everywhere north of about 58°S.
When and where to look for Gemini
Gemini crosses the meridian — its highest point in the sky — at local midnight around January, which makes the months from December to February the easiest time to find it in the evening. It spans declinations +12.9° to +31.9°, so visible from everywhere north of about 58°S.
The quickest way to find it is to open the live AR sky map and point your phone at the sky — if Gemini is above your horizon right now, its figure is drawn in the position it genuinely occupies above you.
Brightest stars in Gemini
| Star | Mag | Type | Distance |
|---|---|---|---|
| PolluxBeta Geminorum | 1.14 | K0IIIb | 33.8 ly |
| CastorAlpha Geminorum | 1.58 | A2V | 51 ly |
| Alhena24Gam Gem | 1.93 | A0IV | 109.3 ly |
| Castor B66Alp Gem | 2.85 | A m | 51.5 ly |
| Tejat13Mu Gem | 2.87 | M3IIIvar | 231.6 ly |
| Mebsuta27Eps Gem | 3.06 | A3mA6-A9 | 845 ly |
Magnitude runs backwards: lower numbers are brighter, and anything below about 6.5 is beyond the naked eye under a dark sky.
What Gemini is made of
The catalogue lists 119 stars within Gemini, of which 119 are magnitude 6.5 or brighter — the limit of what an unaided eye picks up under a genuinely dark sky. The rest need binoculars or a telescope.
Spectral make-up
Spectral class is a temperature ordering, running from O at around 30,000 K down to M below 3,500 K. A constellation is a direction, not a group, so this is simply what happens to lie along that line of sight.
The closest catalogued star in this direction is Pollux at 33.8 light years. The most distant is HD 58050 at roughly 3,167 light years — stars that appear side by side here are nothing of the sort.