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79 Cards in this Set
- Front
- Back
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angular diameter
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arc angle across an object
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annular eclipse
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an eclipse of the sun in which the moon is too distant to cover the sun completely, so a ring of sunlight is seen around the moon
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arc angle
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measurement of the angle between two objects or two parts of the same object
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celestial equator
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a great circle on the celestial sphere 90° from the celestial poles
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celestial poles
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points about which the celestial sphere appears to rotate
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celestial sphere
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a hypothetical sphere of very large radius centered on the observer; the apparent sphere of the night sky
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circumpolar star
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all the stars that never set at a given latitude; all the stars between Polaris and the northern horizon
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constellation
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any of the 88 contiguous regions that cover the entire celestial sphere
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declination
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the coordinate on the celestial sphere exactly analogous to latitude on earth; measured north and south of the celestial equator
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degree
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a unit of angular measurement
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diurnal motion
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cyclic motion with a one-day period
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eclipse path
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the track of the tip of the moon's shadow along the earth's surface during a total or annular solar eclipse
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ecliptic
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the annual path of the sun on the celestial sphere; the plane of the earth's orbit around the sun
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equinox
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either of the two days of the year when the sun crosses the celestial equator and is therefore directly over the earth's equator
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gravitation
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tendency of all matter to attract all other matter
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line of nodes
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the line along which the plane of the moon's orbit intersects the plane of the ecliptic
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lunar eclipse
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an eclipse during which the earth blocks light that would have struck the moon
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lunar phase
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names given to the apparent shapes of the moon as seen from the earth
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north celestial pole
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the location on the celestial sphere directly above the earth's northern rotation pole
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partial eclipse
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a lunar or solar eclipse in which the eclipsed object does not appear completely covered
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penumbra
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the portion of a shadow in which only part of the light source is covered by the shadow making body
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penumbral eclipse
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a lunar eclipse in which the moon passes only through the earth's penumbra
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precession
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slow, conical motion of the earth's axis of rotation caused by the graviational pull of the moon and sun on the earth's equatorial bulge
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precession of the equinoxes
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the slow, westward motion of the equinoxes along the ecliptic because of earths precession
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revolution
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the orbit of one body around another
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right ascension
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the celestial coordinate analogous to longitude on earth and measured around the celestial equator from the vernal equinox
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rotation
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the spinning of a body about an axis passing through it
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sidereal month
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the period of the moon's revolution about the earth measured with respect to the moon's location among the stars
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sideral period
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the orbital period of one object about another measured with respect to the stars
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solar corona
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the sun's outer atmosphere
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solar day
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from noontime to the next noontime; for earth 24 hours
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solar eclipse
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an eclipse during which the moon blocks the sun
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south celestial pole
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the location on the celestial sphere directly above the earth's south rotation pole
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summer solstice
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the point on the ecliptic where the sun is farthest north of the celestial equator
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synodic month
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the period of revolution of the moon with respect to the sun; the length of one cycle of lunar phases
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terminator
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the line dividing day and night on the surface of the any body orbiting the sun; the line of sunset or sunrise
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total eclipse
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sun is completely hidden by the moon
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umbra
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the central, completely dark portion of a shadow
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vernal equinox
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point on the ecliptic where sun crosses the celestial equator from south to north; beginning of spring
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winter solstice
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sun is farthest south from equator
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zenith
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the point on the celestial sphere directly overhead
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geocentric
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belief that earth is at center of universe
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cosmology
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theory of overall structure and evolution of universe
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direct motion
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gradual, eastward motion of a planet against the background of stars as seen from earth
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retrograde motion
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the occassional backward (westward) apparent motion of a planet against the background stars as seen from earth (illusion)
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heliocentric
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sun centered
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configurations
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a particular geometric arrangement of the earth, a planet, and the sun
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inferiour conjunction
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the configuration when mercury or venus is directly between the sun and the earth
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superiour conjunction
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the configuration when a planet is behind the sun as seen from earth
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elongation
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the angle between a planet and the sun as seen from earth
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parallax
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the variation in angle that occurs when viewing a nearby object from different places
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focus
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the two points inside an ellipse
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major axis
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longest diameter across and ellipse
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semimajor axis
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half of the longest dimension of an ellipse
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orbital eccentricity
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the shape of a planet's orbit around the sun
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perihelion
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planet is nearest the sun
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aphelion
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planet is farthest from sun
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law of equal areas
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keplers second law each planet's speed decreases as it moves from perihelion to aphelion
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astronomical unit
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the average distance between the earth and sun
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galilean moons
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four moons near jupiter
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acceleration
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rate at which velocity changes with time
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mass
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total number of particles it contains
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weight
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force with which you push down on a scale due to gravity...
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conservation of angular momentum
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total amount of angular momentum in an isolated system remains constant
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angular momentum
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measurement of how much energy is stored in an object due to its rotation and revolution
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solar system
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one star, the sun, and everything that orbits it
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solar nebula
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the cloud of gas and dust from which the sun and the rest of the solar system formed
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protosun
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the sun prior to the time when hydrogen fusion began in its core
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protoplanetary disks (proplyd)
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a disk of material encircling a protostar or a newborn star
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planetessimals
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primordial asteriodlike object from which planets accreted
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protoplanets
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the embryonic stage of a planet when it is growing because of collisions with planetessimals
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accretion
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the gradual accumulation of matter by an astronomical body
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orbital inclinations
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tilt or angle of an objects orbital plane around the sun compared to the ecliptic
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craters
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circular depression
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asteroids
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any rocky object larger then a few hundred meters in diameter
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terrestrial planets
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any of the planets mercury venus earth or mars; composition and density similar to earth
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albedo
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fraction of sunlight that a planet, asteriod, or satellite scatters directly back into space
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extrasolar planets
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planets outside the solar system
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radial motion
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motion toward or away from us
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