Star Stars · In Gemini
Alhena
Alhena, γ Geminorum, is a white subgiant in Gemini: the 45th brightest star in the night sky.
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- Constellation
- Gemini
- Designation
- γ Geminorum
- Apparent magnitude
- 1.93 · 45th brightest star in the night sky
- Spectral class
- A0IV
- Distance
- 109 light-years
- Highest at midnight
- late December
- Position (J2000)
- RA 06h 38m · Dec +16° 24′
A white subgiant, around 10,000 K, like Sirius and Vega. About 67× brighter than the faintest star the eye can see. Gives off about 160 times the Sun's visible light. The light you are seeing left around 1917.
When to see it
On the night of Mon 28 Dec 2026, when it is highest around midnight, on each city’s own clock:
| From | Rises | Highest | Sets |
|---|---|---|---|
| London GMT | 16:44 | 00:09 · 55° | 07:35 |
| New York EST | 17:07 | 00:04 · 66° | 07:02 |
| Singapore GMT+8 | 19:14 | 01:15 · 75° | 07:15 |
| Sydney GMT+11 | 19:52 | 01:06 · 40° | 06:19 |
Common questions
- Can I see it from 50° north?
- Yes. It rises and sets, and at its highest it stands 56° up in the south.
- Can I see it from 35° south?
- Yes. It rises and sets, and at its highest it stands 39° up in the north.
- When is the best time of year to see it?
- Around late December, when it stands opposite the Sun and is highest at midnight. It comes round about two hours earlier each month, so by late March it is highest in the early evening, and in late September not until the hours before dawn.
- How far away is it, and how bright?
- It is 109 light-years away, and shines at magnitude 1.93 in our sky. From that far, the Sun would be a star of magnitude 7.4: too faint for the eye, a target for binoculars.
- Naked eye, binoculars or telescope?
- The naked eye, even from a city: at magnitude 1.93 it is brighter than the faintest stars a city sky still shows, about magnitude 4.5.
Look for
Start from Betelgeuse: Alhena is 14° north-east of it, a fist and a half at arm’s length.
Look for
From 50° north it climbs to 56°; from 35° north it climbs to 71°; from the equator it climbs to 74°; from 35° south it climbs to 39°.
Science
Alhena’s surface is about 10,000 K, some 4,200 K hotter than the Sun’s 5,772 K, so its light is strongest at about 290 nm, in the ultraviolet, past the violet end of what the eye can see, where the Sun’s is strongest at 500 nm. Moved to 33 light-years, the distance astronomers compare stars at, it would shine at magnitude −0.7, about as bright as Canopus looks to us.
Did you know
Against Betelgeuse, the brighter star the hop starts from: Betelgeuse looks 3.9 times as bright as Alhena in our sky; Betelgeuse is 498 light-years away and Alhena 109 light-years, so side by side Betelgeuse would give off 81 times as much light as Alhena.
Science
Alhena is the 57th nearest to us of the 156 stars on these pages with a measured distance. Its nearest neighbour among them in space is Elnath, about 50 light-years from it; on our sky the two are 20° apart.
Look for
The Sun passes 6.7° north of Alhena around late June, when it is highest at noon, in daylight: the weeks either side are its worst time of year. From 50° north it is above the horizon for about 15 hours a day, from 35° north about 14 and from 35° south about 10. It is 4° from the plane of the Milky Way, inside the band a dark sky shows.