Gemini is the constellation named after the twins Castor and Pollux. Its name is Latin for “twins,” and the two bright stars at its northern end are traditionally imagined as the heads of the mythological brothers.
In Greek mythology, Castor and Pollux were known together as the Dioscuri. Castor was mortal, while Pollux was the son of Zeus and therefore immortal. When Castor died, Pollux asked Zeus not to separate them permanently. Zeus placed the brothers together in the heavens, where they became Gemini.
The constellation is one of the zodiac constellations and was included in Ptolemy’s second-century catalogue. It lies between Taurus and Cancer, with Orion nearby to the southwest. Gemini is especially easy to recognize in Northern Hemisphere winter skies because Castor and Pollux stand out as a close pair.
Although their names are paired, the stars are not twins in a physical sense. Pollux is an orange giant and the brighter of the two, while Castor is a complex sextuple star system. Their visual pairing is mythological, not evidence that they form a single binary star.