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29 Cards in this Set
- Front
- Back
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fixed in space with respect to Earth's axis and Sun's direction at vernal equinox
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celestial coordinates right ascension and declination
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We would be more likely to get an accurate measurement of the distance from Earth to a nearby star if we took the angular measurements at times separated by what time interval?
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6 months apart
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A star overhead will move through what angle in the course of one hour?
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15 degrees
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What is the primary observable effect of the slow precession of Earth's rotational axis?
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It causes the set of constellations visible on any fixed night each year to change over many years.
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What distance would light travel through empty space in one year?
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about 10 trillion kilometers (1012 km)
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Why are the stars Betelgeuse and Rigel also known as alpha and beta Orionis?
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They are the two brightest stars in the constellation Orion
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Night and day have approximately equal length at what time or times of the year?
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vernal and autumnal equinoxes
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What is the length of time needed for the Earth's rotation axis to complete one cycle of precession?
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26,000 years
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How much longer is one solar day on Earth than one sidereal day?
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3.94 Minutes
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What is longer, a solar day or siderial day?
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A solar day
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1 * 10^9 is how long?
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50 years
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how long is 1 * 10^6?
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2 weeks at 16 hrs a day
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how long is 1000?
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16 minutes
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how is the astronomical perspective measured?
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scientific notation
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What is a light year?
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the distance that light travels in one year with a speed ~3000,000 km/s = 3*10^5 km/s
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how many constellations are there?
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88 total
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who named the constellations?
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Greeks
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Constellations
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human nature to group things
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revolution
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365 days
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rotation
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1 day
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Right Assension and Declination
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can find any star (object) at any time
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how long is a solar day?
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24 hours
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how much does the earth rotate during a solar day?
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360.986 degrees
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how long is a sidereal day
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3.9 minutes shorter than a solar day
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what does greek "sidus" mean?
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star
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what does day mean?
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period
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a sidereal day means
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of time to rotate once relative to the background stars.
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equation for distance?
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360*baseline
_____________ =r 2 (pi) * parallax |
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equation for diameter? (baseline)
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2(pi)r*parallax
--------------- = baseline 360 (degrees) |
