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31 Cards in this Set
- Front
- Back
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Costellation
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is a region of the sky with well-defined borders.
Note: The names and borders of the 88 official constellations werre chosen in 1928 by members of the International Astronomical Union (IAU). |
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Celestial Sphere
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is an imaginary sphere of gigantic radius with the Earth located at its center.
Note: We identify four special points and circles. |
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The North Celestial Pole
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is the point directly over the Earth's North pole.
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The South Celestial Pole
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is the point directly over the Earth's South Pole.
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The Celestial Equator
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is a projection of Earth's equator into space, it makes a complete a complete circle around the celestial sphere.
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The ecliptic
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is the path the Sun follows as it appears to circle around the celestial sphere once a year.
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Local sky
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is the half of the celestial sphere that we see at any time form any point from where we are standing.
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Horizon
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is the boundary between the Earth and the sky. In other words, where the Earth touches the sky.
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The zenith
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is the direction pointing directly "above" a particular location.
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The meridian
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is an imaginary half circle stretching from the horizon due South, through the zenith, to the horizon due North.
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Altitude
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is the angular distance between the horizon and an object in the sky (above horizon).
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Angular size or angular distance
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A measures of the angle formed by extending imaginary lines outward from our eyes to span an object ( or the space between two objects).
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Arcminute VS Arcsecond
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(minute of arc) 1/60 of 1º
(second of arc) 1/60 of an arcminute, or 1/3600 of 1º. |
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Circumpolar stars
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are start that never set or rise but instead make daily counterclockwise circles around the north celestial pole.
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What is the spring equinox?
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occurs around March 21, is the moment when the Northern Hemisphere goes from being tipped lightly away from the Sun to being tipped slightly toward the Sun.
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What is the fall equinox?
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occurs around September 22, is the moment when the Northern Hemisphere first starts to be tipped away from the Sun.
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What is latitude?
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measures from North-South position; it is defined to be at 0º at the equator, increasing to 90ºN at the North Pole and 90ºS at the South Pole.
Note: the lines of latitude are actually circles running parallel to the equator. |
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What is longitude?
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measures East-West positions, so lines of longitude are semicircles extending from North Pole to South Pole.
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What is the meridian?
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the line of longitude that passes through Greenwich, England; defined to be longitude 0º.
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What is procession?
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a gradual wobble that alerts the orientation of Earth's axis in space.
NOTE: each cycle of Earth's precession takes about 26,000. |
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What is an Eclipse?
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an event in which one astronomical object cast a shadow on another or crosses our line of sight to the other object.
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What is a lunar eclipse?
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occurs when Earth lies directly between the Sun and the Moon, so that Earth's shadow falls on the Moon?
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What is a solar eclipse?
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occurs when the moon lies directly between the Sun and the Earth.
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Conditions for eclipses:
The Sun, Earth, and Moon with every new and full moon. However, we don't have both lunar and solar eclipse every month... why? |
Because the moon's orbit is slightly inclined (by about 5º) to the ecliptic plane (the plane of Earth's orbit around the Sun).
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What is nodes?
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The two points in the Moon's orbit where it crosses the ecliptic plane.
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What is rotation?
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the spinning of an object around its axis.
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What is waning?
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the set of phases in which less and less of the visible face of the Moon is illuminated; the phases that come after full Moon but before full Moon.
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What is waxing?
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The set of phases in which more and more of the visible face of the moon is becoming illuminated; the phases that come after new Moon, but before full Moon.
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What is gibbous?
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The phase of the Moon (or of a planet) in which more than half but less than all the visible face is illuminated by sunlight.
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what is crescent?
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The phases of the Moon (or a planet) in which just a small portion (less than half) of the visible face is illuminated by sunlight.
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What is the Zodiac?
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the constellations on the celestial sphere through which the ecliptic passes.
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