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Universe 9th Ed Vocab CH 1-4
Just a bunch of definitions.
47
Astronomy
Undergraduate 1
10/06/2010

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Term
Angular Distance
Definition
The angle between two points in the sky.
Term
Acceleration
Definition
The rate at which an object's velocity changes due to a change of speed or direction.
Term
Angular Diameter
Definition
The angle subtended by the diameter of an object. It is used to describe the apparent size of a celestial object.
Term
Angular Measure
Definition
The size of an angle, usually expressed in degrees, arcminutes or arcseconds.
Term
Annular Eclipse
Definition
An eclipse of the sun in which the moon is too distant to cover the sun completely, so that a ring of sunlight is seen around the moon at mideclipse.
Term
Antarctic Circle
Definition
A circle of latitude 23 and a half degrees north of the Earth's south pole.
Term
Aphelion
Definition
The point in its orbit where a planet is farthest from the sun.
Term
Apogee
Definition
The point in its orbit where a satellite or the Moon is farthest from Earth.
Term
Apparent Solar Day
Definition
The interval between two successive transits of the Sun's center across the local meridian.
Term
Apparent Solar Time
Definition
Time reckoned by the position of the sun in the sky.
Term
Arcminute
Definition
One sixtieth (1/60) of a degree, designated by the symbol '.
Term
Arcsecond
Definition
One sixtieth (1/60) of an arcminute or 1/3600 degree, designated by the symbol ".
Term
Arctic Circle
Definition
A circle of latitude 23 and a half degrees south of Earth's north pole.
Term
Astronomical Unit
Definition
The semimajor axis of Earth's orbit- the average distance between Earth and the Sun (AU).
Term
Autumnal Equinox
Definition
The intersection of the ecliptic and the celestial equator where the Sun crosses the equator from north to south. Also used to refer to when the sun passes through this intersection.
Term
Celestial Equator
Definition
A great circle on the celestial sphere 90 degrees from the celestial poles.
Term
Celestial Poles
Definition
The points about which the celestial sphere appears to rotate.
Term
Celestial Sphere
Definition
An imaginary sphere of very large radius centered on an observer; the apparent sphere of the sky.
Term
Circumpolar
Definition
A term describing a star that neither rises nor sets but appears to rotate around one of the celestial poles.
Term
Conic Section
Definition
The curve of intersection between a circular cone and a plane; this curve can be a circle, ellipse, parabola or hyperbola.
Term
Conjunction
Definition
The geometric arrangement of a planet in the same part of the sky as the sun, so that the planet is at an elongation at 0 degrees.
Term
Constellation
Definition
A configuration of stars in the same region of the sky.
Term
Declination
Definition
Angular distance of a celestial object north or south of the celestial equator.
Term
Deferent
Definition
A stationary circle in the Ptolemaic system along which another circle (an epicycle) moves, carrying a planet, the Sun, or the moon.
Term
Direct Motion
Definition
The apparent eastward motion of a planet as seen against the background stars.
Term
Diurnal Motion
Definition
Any apparent motion in the sky that repeats on a daily basis, such as the rising and setting of stars.
Term
Eccentricity
Definition
A number between 0 and 1 that describes the shape of an ellipse.
Term
Eclipse Path
Definition
The track tip of the Moon's shadow along the Earth's surface during a total or annular solar eclipse.
Term
Eclipse Year
Definition
The interval between successive passages of the sun through the same node of the moon's orbit.
Term
Eclipse Year
Definition
The interval between successive passages of the sun through the same node of the moon's orbit.
Term
Ecliptic
Definition
The apparent annual path of the sun on the celestial sphere.
Term
Ecliptic Plan
Definition
The plane of Earth's orbit around the Sun.
Term
Ellipse
Definition
A conic section obtained by cutting completely through a circular cone with a plane.
Term
Elongation
Definition
The angular distance between a planet and the Sun as viewed from Earth.
Term
Epicycle
Definition
A moving circle in the Ptolemaic system about which a planet revolves. Part of the geocentric model.
Term
Epoch
Definition
The date used to define the coordinate system for objects on the sky.
Term
Equinox
Definition
One of the intersections of the ecliptic and the celestial equator. Also used to refer to the date on which the sun passes through such an intersection.
Term
first quarter moon
Definition
The phase of the moon that occurs when the moon is 90 degrees east of the sun.
Term
focus (of an ellipse)
Definition
One of the two points inside an eplipse such that the combined distance from the two foci to any point on the ellipse is a constant.
Term
Force
Definition
A push or pull that acts on an object.
Term
Full moon
Definition
A phase of the moon during which its full daylight hemisphere can be seen from Earth.
Term
Geocentric Model
Definition
An Earth-centered theory of the universe.
Term
Gravity
Definition
The force with which with all matter attracts all other matter.
Term
Greatest Eastern Elongation
Definition
The configuration of an inferior planet at its greatest angular distance east of the sun.
Term
Greatest Western Elongation
Definition
The configuration of an inferior planet at its greatest angular distance west of the sun.
Term
Heliocentric model
Definition
A sun-centered theory of the universe.
Term
Hyperbola
Definition
A conic section formed by cutting a circular cone with a planet at an angel steeper than the sides of the cone.
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