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34 Cards in this Set
- Front
- Back
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What does apparent visual magnitude not take into account?
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- It does not take into account the distance to the stars.
- It tells you only how bright the star looks as seen from Earth |
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What is flux?
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- A measure of the light energy from a star that hits one square meter in one second
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What is the equation to find out the intensity ratio of two stars?
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Ia/Ib= (2.512)^(mb-ma)
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How do you find the magnitude difference between two stars?
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mb-ma=2.5log (Ia/Ib)
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In which direction does the sky appear to move? (think of the sun)
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- It appears to move westward
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In which direction does the Earth rotate?
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- It rotates to the east
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What are the north and south points?
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- They are the points on the horizon closest to the celestial poles
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What are the east and west points?
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- The celestial equator always touches the horizon at the east and west points.
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How can you measure distances in the sky?
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- Through angular distances
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What is the angular diameter?
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- Angular distance from one edge to the other
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What does the angular distance from the horizon to the north celestial pole always equal?
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- The latitude
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What are circumpolar constellations?
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- Those are those that never rise or set. At high latitudes there are more circumpolar constellations and at the equator, there are none.
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How long is one cycle of Earth's precession?
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- 26,000 years
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What is the difference between revolution and rotation?
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- Revolution is the orbit around the sun and rotation is the spinning on its axis
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In relation to the stars in the sky, in what direction does the Sun move?
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- It moves to the east
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What is the ecliptic?
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- It is the apparent path of the sun against the background of stars
- It "travels" about 1 degrees eastward in 24 hours |
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What is an equinox?
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- When the sun crosses the celestial equator
- This is the vernal and the autumnal |
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What is the summer solstice?
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-The sun is at its furthest north of the celestial equator
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What is the winter solstice?
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- The sun is at its furthest south of the celestial equator
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What is perihelion?
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- Closest point to the sun in the orbit
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What is aphelion?
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- The earth is the most distant from the Sun.
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Exactly how long is a month?
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- 29.5 days
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How long does it take for the moon to revolve the Earth?
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- Approximately 27 days
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What is the calendar year?
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- 365.24 days
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What are the days of the week named after?
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- The seven "naked-eye" constellations that appear to move among the constellations.
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In which direction does the moon travel in the night sky?
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- It moves eastward
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What is the meridian?
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- It is an imaginary line that goes through the zenith, nadir, and the celestial poles, and is perpendicular to the horizon
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Is noon AM or PM?
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- It's neither.
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What is the analemma?
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- It is the figure-8 curve you get when you mark the position of the Sun in the sky for 365 days
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What is the actual time for the Earth to spin completely?
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- 23h 56m 4.1s
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What is sidereal time?
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- The actual time based on the stars, and this is different from the solar time, which is based on the sun
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How fast does Mercury go around the sun?
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- 50 km/sec
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How fast does Earth go around the sun?
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- 30 km/sec
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How fast does Pluto go around the sun?
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- 4 km/sec
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