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rotation
motion around an axis passing through the rotating body
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revolution
orbital motion about a point located outside the orbiting body
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ecliptic
the apparent path of the sun around the sky
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vernal equinox
the place on the celestial sphere where the sun corsses the celestial equator moving northward. Also, the time of the year when the sun crosses this point, about march 20, and spring begins in the northern hemisphere
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summer solstice
the point on the celestial sphere where the sun is at its most notherly point.
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autumnal equinox
the point on the celestial sphere where the sun crosses the celestial equator going southward
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winter solstice
the point on the celestial sphere where the sun is fathest south
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perihelion
the orbital point of closest approach to the sun
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aphelion
the orbital point of greatest distance from the sun
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lunar eclipse
the darkening of the moon when it moves through earth's shadow
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umbra
the region of a shadow that is totally shaded (pg 30)
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penumbra
the portion of a shadow that is only partically shaded
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totality
the period of total eclipse
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sidereal period
the time a celestial body takes to turn once on its axis or revolve once around its orbit relative to the stars
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synodic period
the time a solar system body take to orbit the sun once and return to the same orbital period referenced to Earth.
for the moon, this is the time for the moon to orbit.
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solar eclipse
the even that occurs when the moon passes directly between the sun, blocking our view of the sun
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photosphere
the bright visible surface of the sun
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chromosphere
bright gases just above the photosphere of the sun
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corona
on the sun, the faint outer atmosphere composed of low-density, high temperature gas
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prominence
eruption on the solar surface; most visible during total solar eclipses
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diamond ring effect
during a total solar eclipse, the momentary appearance of a spot of the photosphere at the edge of the moon, producing a brilliant glare set in the silvery ring of the corona
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Saros cycle
an 18 year, 11.33- day period after which the pattern of lunar and solar eclipses repeats
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Milankovitch hypothesis
suggestions that Earth's climate is determined by slow periodic changes in the shape of this orbit, the angle of its axsis and precession
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