Aries
in astronomy, the constellation Aries, or the Ram, one of the ancient ARIOSTO zodiacal constellations, and generally called the first sign of the zodiac; also the portion of the ecliptic between 0º and 30° longitude, which the sun enters on March 21st (the vernal equinox). The constellation Aries, from which the region derives its name, was once within its limits, but now, by the precession of the equinoxes, it has gradually moved into the space anciently assigned to Taurus. It is denoted by the Greek symbol, Gamma, which remotely resembles a ram's head.
The first point of Aries is the spot in the heavens where the sun appears to stand at the vernal equinox. It is not marked by the presence of any star, but it is not very far from the third star of Pegasus, that called Algenib. It is the point from which the right ascensions of the heavenly bodies are reckoned upon the equator and their longitudes upon the ecliptic.