Gemini

GeminiThe constellation Gemini, as depicted in an illumination from a Book of Hours, Italian, c. 1475; in the Pierpont Morgan Library, New York City (MS. G.14).

Gemini, in astronomy, zodiacal constellation lying in the northern sky between Cancer and Taurus, between about 6 and 8 hours right ascension and between 10° and 35° north declination. Its brightest stars are Castor and Pollux (Alpha and Beta Geminorum); Pollux is the brighter of the two, with a magnitude of 1.15, and is the 17th brightest star in the sky. Castor has a magnitude of 1.58. In the Northern Hemisphere, the summer solstice, the northernmost point reached by the Sun in its annual apparent journey among the stars and the longest day of the year, lies in Gemini. This constellation also contains the isolated pulsar Geminga.

Hand-colored etching by Sidney Hall depicting the constellation Gemini as the twins Castor and Pollux, surrounded by labeled stars.
GeminiAstronomical chart showing the twins Castor and Pollux forming the constellation Gemini; hand-colored etching by Sidney Hall from Urania's Mirror, 1825.

Because Gemini has two bright stars near to each other, it is often represented by a set of twins or a pair of animals. In Mesopotamia about 1100 bce, Gemini’s brightest stars were called Lugalgirra and Meslamta-Ea, who were twin gods. In addition to their identification as Castor and Pollux, the twins have also been related to other celebrated pairs, such as the younger and older Horus or Romulus and Remus. In Egyptian astrology the constellation was represented as a pair of goats, and in Arabian astrology as a pair of peacocks.

Medieval manuscript illustration of Gemini shows two figures, one in blue and red and one in green, holding each other inside a gold circle surrounded by red stars and handwritten text.
GeminiGemini (twins), watercolor and ink on paper, from a manuscript created in Ulm or Augsburg, Germany, c. 1464; in the J. Paul Getty Museum, Los Angeles.

In astrology, Gemini is the third sign of the zodiac, considered as governing the period from May 21 to June 21. (The Sun is actually in Gemini from June 21 to July 20.) Gemini is one of the three air signs, along with Aquarius and Libra. Of the three air signs, Gemini has a mutable modality, meaning that it relates to changing situations. Traits associated with those born under the sign of Gemini may include being curious, quick-witted, and inconsistent.

The Editors of Encyclopaedia BritannicaThis article was most recently revised and updated by Erik Gregersen.
Citation Information
Article Title: Gemini
Website Name: Encyclopaedia Britannica
Publisher: Encyclopaedia Britannica, Inc.
Date Published: 01 June 2026
Access Date: November 15, 2026