Gemini

Gem · genitive Geminorum · northern sky

The Gemini figure as the IAU defines it, drawn looking south with east to the left — the orientation you see standing outside.

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

StarMagTypeDistance
PolluxBeta Geminorum1.14K0IIIb33.8 ly
CastorAlpha Geminorum1.58A2V51 ly
Alhena24Gam Gem1.93A0IV109.3 ly
Castor B66Alp Gem2.85A m51.5 ly
Tejat13Mu Gem2.87M3IIIvar231.6 ly
Mebsuta27Eps Gem3.06A3mA6-A9845 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

B11
A26
F17
G19
K35
M11

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.

Nearby constellations