Constellation, Twins
Gemini
The twins Castor and Pollux, brothers of Greek myth, marked by two bright stars side by side. Some star maps show them instead as Apollo and Heracles.
From New York on October 13, 2026, the centre of Gemini rises at 11:02 PM, is highest at 6:36 AM (74° above the horizon in the S) and sets at 2:15 PM.
In the 3D sky
The sky over New York turned towards Gemini. Drag to look around.
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Evening visibility over the year
Height of the constellation’s centre above the horizon at 10 pm local time on the 15th of each month, from New York. Above about 30° it is well placed.
Name and history
Aratus called these stars simply the Twins, and Eratosthenes named them as Castor and Pollux, the Dioscuri, sons of Queen Leda of Sparta. In the most common version Pollux was a son of Zeus and immortal, while Castor was the son of Leda’s mortal husband, King Tyndareus. When Castor was killed in a fight, Pollux grieved and asked Zeus to let them share his immortality. Zeus placed them side by side among the stars. Sailors saw them as their protectors at sea. Hyginus reports another view, that the pair are Apollo and Heracles.
Castor received the letter alpha in Johann Bayer’s atlas of 1603, although Pollux is the brighter of the two. Bayer lettered the brightest stars of Gemini by their position, not their brightness. Propus, at the forward foot of Castor, comes from the Greek for forward foot. In China most of the figure formed Jing, the Well, which named one of the lunar mansions.
Sources: Ian Ridpath, Star Tales: Gemini
Brightest stars
| Star | Designation | Magnitude | Distance |
|---|---|---|---|
| Pollux | β Gem | 1.16 | 34 light-years |
| Castor | α Gem | 1.58 | 51 light-years |
| Alhena | γ Gem | 1.93 | 109 light-years |
| Castor B | α Gem | 2.85 | 52 light-years |
| Tejat | μ Gem | 2.87 | 232 light-years |
| Mebsuta | ε Gem | 3.06 | 845 light-years |
| Propus | η Gem | 3.31 | 385 light-years |
| Alzirr | ξ Gem | 3.35 | 59 light-years |
| Wasat | δ Gem | 3.50 | 61 light-years |
| κ Gem | κ Gem | 3.57 | 141 light-years |
Facts
| Area | about 516 square degrees (30 of 88) |
|---|---|
| IAU abbreviation | Gem |
| Sky | Northern sky |
| Origin | Listed in Ptolemy’s Almagest, about AD 150, from older Greek tradition |
| Stars brighter than magnitude 5 | 26 |
| Centre (J2000) | 7.2 h, 25° |
Deep-sky objects
Galaxies, clusters and nebulae brighter than magnitude 9, from the OpenNGC catalogue. Most need binoculars or a telescope and a dark sky.
| Object | Type | Magnitude |
|---|---|---|
| M35 | Open cluster | 5.1 |
| NGC2129 | Open cluster | 6.7 |
| IC0444 | Reflection nebula | 7.0 |
| NGC2395 | Open cluster | 8.0 |
| NGC2420 | Open cluster | 8.3 |
| IC2157 | Open cluster | 8.4 |
| NGC2331 | Open cluster | 8.5 |
| NGC2158 | Open cluster | 8.6 |
Boundaries: International Astronomical Union, via Astronomy Engine. Areas are computed from the boundaries by sampling (within about one percent). Names and lines: Stellarium. Stars: HYG Database. Deep-sky objects: OpenNGC. Calculated with Astronomy Engine, an open-source library verified against the US Naval Observatory and NASA JPL. Data sources
How to use this page
Choose your place and a night at the top. The answer and the 3D view show where the constellation is, when it is highest and whether it rises at all from where you are. The chart shows its stars and lines, and the tables list its brightest stars and the deep-sky objects inside it.
Frequently asked questions
When is a constellation best seen?
When it is highest in a dark sky, which the page gives for the night you pick. Each constellation is best placed in a particular season, because the stars rise about four minutes earlier every night.
Why can I not see a constellation from my place?
Constellations far south of the celestial equator never rise from northern places, and those far north never rise from southern ones. The page says when this is the case.
What are the constellation boundaries?
The International Astronomical Union divides the sky into 88 areas with official boundaries. The stick figures are only a drawing aid, the boundaries say which constellation a point in the sky belongs to.
Related guides
- How to learn the constellationsStart with one bright pattern you cannot miss, use it as a signpost to its neighbours, and come back a month later: the sky will have turned, and you will know a little more of it.
- Altitude and azimuth: finding things in the skyTwo angles tell you exactly where to look: which direction, and how high.
- Light pollution and dark skies: the Bortle scaleFrom a city centre you can count a few dozen stars. From a truly dark site you can count a few thousand, with the Milky Way bright enough to cast a shadow. The Bortle scale puts a number on the difference.
- Binoculars for stargazing: what to buy and what to look atA pair of 7x50 or 10x50 binoculars shows the craters of the Moon, the moons of Jupiter, dozens of star clusters and the Andromeda Galaxy, for a fraction of the cost of a telescope.