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60 Cards in this Set
- Front
- Back
Astronomy
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The study of the objects that lie beyond our planet Earth, and of the processes by which these objects interact with one another
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Historical Science
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What we observe has already happened in the universe and we can do nothing to change it
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Light Year
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The distance that light travels in one year
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Planet
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A body of significant size that orbits a star and does not produce its own light
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Brown Dwarfs
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A class of objects intermediate between stars and planets; are failed stars- balls of hot gas that do not have what it takes to keep producing significant amounts of light
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Galaxy
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Group of stars
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Dark Matter
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Nonluminous mass, whose presence can be inferred only because of its gravitational influence on luminous matter; composition is not known
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Universe
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Everything that exists that is accessible to our observations
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Quasars
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Brilliant centers of galaxies, glowing with the light of some extraordinarily energetic process
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Geocentric
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Earth-centered
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Zenith
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The top of the dome that is directly above your head
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Horizon
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The line where the dome meets the Earth
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Celestial Sphere
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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
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Axis
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The imaginary stick that our planet rotates on
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North Celestial Pole & South Celestial Pole
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The points where the axis meets the celestial sphere
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Celestial Equator
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A great circle on the celestial sphere 90 degrees form the celestial poles; where the celestial sphere intersects the plane of the Earth's equator
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North Circumpolar Zone
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The area within 38 degrees of the North pole
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South Circumpolar Zone
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The area within 38 degrees of the South Pole
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Ecliptic
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The path the Sun appears to take around the celestial sphere each year
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Constellation
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One of 88 sectors into which astronomers divide the celestial sphere; many constellations are named after a prominent group of stars within them that represents a person, animal, or legendary creature form ancient mythology
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Zodiac
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A belt around the sky about 18 degrees wide centered on the ecliptic
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Cosmology
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Our concept of the cosmos (its basic structure and origin)
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Parallax
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The apparent shift in the direction of an object as a result of the motion of the observer
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Stellar Parallax
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The shift in the apparent direction of a star due to the Earth's orbital motion
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Magnitude
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A system for 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
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Retrograde Motion
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An apparent westward motion of a planet on the celestial sphere or with respect to the stars
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Epicycle
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A circular orbit of a body in the Ptolemaic system, the center of which revolves about another circle
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Ellipse
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A flattened circle
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Focus
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One of two fixed points inside an ellipse from which the sum of the distances to any point on the ellipse is a constant
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Major Axis
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The widest diameter of an ellipse
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Semimajor Axis
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Half the distance of the major axis; usually used to specify the size of the ellipse
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Eccentricity
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The ratio of the distance between the foci to the length of the major axis
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Kepler's First Law
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Each planet moves about hte Sun in an orbit that is an ellipse, with the Sun at one focus of the ellipse
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Kepler's Second Law
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The straight line joining a planet and the Sun sweeps out equal areas in space in equal intervals of time
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Kepler's Third Law
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The squares of the planets' periods of revolution are in direct proportion to the cubes of the semimajor axes of their orbits
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Newton's First Law
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Every body continues doing what it is already doing- being in a state of rest or moving uniformly in a straight line- unless it is compelled to change by an outside force
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Newton's Second Law
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The change of motion of a body is proportional to the force actin on it and is made in the direction in which that force is acting
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Newton's Third Law
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To every action there is an equal and opposite reaction (or the mutual actions of two bodies upon each other are always equal and act in opposite directions)
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Conservation of Angular Momentum
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The law that the total amount of angular momentum in a system remains the same (in the absence of any force not directed toward or away from the point or axis about which the angular momentum is conserved
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Angular Momentum
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A measure of the momentum of an object as it rotates or revolves about some fixed point
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Gravity
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The mutual attraction of material bodies or particles
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Orbit
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The path of an object through space
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Perihelion
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The place in the orbit of an object revolving about the Sun where it is closest to the Sun's center
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Aphelion
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Point in its orbit where an Earth satellite is farthest from the Earth
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Perigee
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The place in the orbit of an Earth satellite where it is closest to the center of the Earth
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Apogee
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Point in its orbit where an Earth satellite is farthest from the Earth
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Asteroid Belt
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The great majority of asteroids in our solar system that lie between 2.2 and 3.3 AU
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Circular Satellite Velocity
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The critical speed that a revolving body must have in order to follow a circular orbit
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Escape Velocity
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The velocity a body must achieve to break away from the gravity of another body and never return to it
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Great Circle
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Any circle on the surface of sphere whose center is at the center of the sphere
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Declination
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Angular distance north or south of the celestial equator
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Right Ascension
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A coordinate for measuring the east-west positions of celestial bodies; the angle measured eastward along the celestial equator from the vernal equinox to the hour circle passing through a body
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Solar Day
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The rotation period of the Earth with respect to the Sun
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Sidereal Day
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Period of the revolution of one body about another measured with respect to the stars
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Apparent Solar Time
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Time as measured by the position of the Sun in the sky (the time that would be indicated by a sundial)
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Mean Solar Time
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Based on the average value of the solar day over the course of the year; contains exactly 24 hours
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Phases
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A particular point in the time of a cycle or any distinct time period in a sequence of events
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Eclipse
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Occurs whenever any part of either the Earth or the Moon enters the shadow of the other
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Solar Eclipse
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When the sun is at least partially covered by the Moon
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Lunar Eclipse
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When the Moon passes into the shadow of the Earth
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