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30 Cards in this Set

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To change velocity; to speed up, slow down, or change direction
An especially noticeable star pattern in the sky, such as the Big Dipper.
The pseudoscience that deals with the supposed influences on human destiny of the configurations and locations in the sky of the Sun, Moon, and planets; a primitive belief system that had its origin in ancient Babylonia.
An imaginary line about which a body rotates.
The angle along the celestial horizon, measured eastward from the north point to the intersection of the horizon with the vertical circle passing through an object.
celestial equator
A great circle on the celestial sphere 90° from the celestial poles; where the celestial sphere intersects the plane of the Earth's equator.
celestial meridian
An imaginary line on the celestial sphere passing through the north and south points on the horizon and through the zenith.
celestial poles
Points about which the celestial sphere appears to rotate; intersections of the celestial sphere with the Earth's polar axis.
celestial sphere
Apparent sphere of the sky; a sphere of large radius centered on the observer. Directions of objects in the sky can be denoted by their position on the celestial sphere.
circumpolar zone
Those portions of the celestial sphere near the celestial poles that are either always above or always below the horizon.
A substance composed of two or more chemical elements.
The apparent annual path of the Sun on the celestial sphere.
A substance that cannot be decomposed by chemical means into simpler substances.
A circular orbit of a body in the Ptolemaic system, the center of which revolves about another circle (the deferent).
A great circle on the Earth, 90° from (or equidistant from) each pole.
Centered on the Earth.
Centered on the Sun.
horizon (astronomical)
A great circle on the celestial sphere 90° from the zenith; more popularly, the circle around us where the dome of the sky meets the Earth.
A chart used by astrologers, showing the positions along the zodiac and in the sky of the Sun, Moon, and planets at some given instant and as seen from a particular place on Earth - usually corresponding to the time and place of a person's birth.
A system of measuring the amount of light flux received from a star or other luminous object. The higher the magnitude, the less radiation we receive from the object.
Any of the nine largest objects revolving about the Sun, or any similar objects that orbit other stars. Unlike stars, planets do not (for the most part) give off their own light but only reflect the light of their parent star.
An optical device for projecting on a screen or domed ceiling the stars and planets and their apparent motions in the sky.
precession (of Earth)
A slow, conical motion of the Earth's axis of rotation caused principally by the gravitational pull of the Moon and Sun on the Earth's equatorial bulge.
precession of the equinoxes
Slow westward motion of the equinoxes along the ecliptic that results from precession.
retrograde (rotation or revolution)
Backward with respect to the common direction of motion in the solar system; clockwise as viewed from the north, and going from east to west rather than from west to east.
retrograde motion
An apparent westward motion of a planet on the celestial sphere or with respect to the stars.
sign (of zodiac)
Astrological term for any of 12 equal sections along the ecliptic, each of length 30°. Because of precession, these signs today are no longer lined up with the constellations from which they received their names.
The period of revolution of the Earth around the Sun.
The point on the celestial sphere opposite to the direction of gravity; the point directly above the observer.
A belt around the sky about 18° wide centered on the ecliptic.