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equinox

(Encyclopedia)equinox ´kwnks [key], either of two points on the celestial sphere where the ecliptic and the celestial equator intersect. The vernal equinox, also known as the first point of Aries, is the poi...

Aries

(Encyclopedia)Aries âr´z [key] [Lat.,=the ram], constellation lying on the ecliptic (the sun's apparent path through the heavens) between Taurus and Pisces; it is one of the constellations of the zodiac. It con...

zodiac

(Encyclopedia)zodiac z´dk [key] [Gr. zoion=animal], in astronomy, zone of the sky that includes about 8° on either side of the ecliptic. The apparent paths of the sun, the moon, and the major planets all fa...

right ascension

(Encyclopedia)right ascension, in astronomy, one of the coordinates in the equatorial coordinate system. The right ascension of a celestial body is the angular distance measured eastward from the vernal equinox alo...

midnight sun

(Encyclopedia)midnight sun, phenomenon in which the sun remains visible in the sky continuously for 24 hr or longer, occurring only in the polar regions. The midnight sun is due to the fact that the plane of the ea...

equatorial coordinate system

(Encyclopedia)equatorial coordinate system, the most commonly used astronomical coordinate system for indicating the positions of stars or other celestial objects on the celestial sphere. The celestial sphere is an...

harvest moon

(Encyclopedia)harvest moon, full moon occurring nearest to the autumnal equinox, about Sept. 23. During harvest moon the retardation (later rising each night) of the moon is at a minimum because of the relation of ...

hour angle

(Encyclopedia)hour angle, in astronomy, a coordinate in the equatorial coordinate system. The hour angle of a celestial body is the angular distance, expressed in hours, minutes, and seconds (one hour equals 15 deg...

April Fool's Day

(Encyclopedia)April Fool's Day or All Fool's Day, holiday of uncertain origin, known for practical joking and celebrated on the first of April. Prior to the adoption of the Gregorian calendar in 1564, the date was ...

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