Gemini. Coloured historical artwork of the constellation of Gemini. The constellation is depicted as a pair of twins, one holding a club, the other a flail. Gemini is the third sign of the Zodiac. The Sun is in Gemini between 21 May and 21 June. It is a prominent constellation, famed for the two bright stars which form the twins' heads; Castor (right) and Pollux (left). The Sun's path, the ecliptic, is shown by the black and red line at centre. This artwork is based on a sky map by the Polish-German astronomer Johannes Hevelius (1611-1687), which was published posthumously in 1690.