Cancer [Lat., = the crab], in astronomy, constellation lying on the ecliptic (the sun's apparent path through the heavens) between Gemini and Leo; it is a constellation of the zodiac. It contains the star cluster Praesepe, but no bright stars. The tropic of Cancer takes its name from this constellation, in which the summer solstice was located about 2,000 years ago. Now, because of the precession of the equinoxes, the summer solstice has moved westward into the constellation Gemini. Cancer reaches its highest point in the evening sky in March.