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42 Cards in this Set
- Front
- Back
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Celestial Sphere
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An imaginary sphere that shows the stars from Earth's perspective.
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Celestial Equator
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Projection of Earth's equator onto the celestial sphere
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Ecliptic
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- the path of the sun accross the sky from earth's perspective
- one circle every year |
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Tilt
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- 23.5 degrees
- the angle between the celestial equator and the ecliptic - and the tilt of Earth's rotation axis |
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Vernal Equinox
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- where the celestial equator and the ecliptic cross
- Earth goes from being tipped away to being closer towards the sun - first day of Spring - day and night of equal length |
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Summer Solstice
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- sun is at its maximum height above the celestial equator
- Northern Hemisphere gets its most direct sunlight - first day of Summer |
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Autumnal Equinox
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- celestial equator and ecliptic cross
- moving from above the celestial equator to below it - first day of autumn |
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Declination
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- number of degrees something is above or below the celestial equator
- below = negative degrees |
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Right Ascension
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- angle measured from the vernal equinox/celestial equator
- measured in hours - 1 hour = 15 degrees |
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Horizon
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where the sky visibly meets the earth
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Altitude
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- the angle of a star above the horizon measured in degrees
- latitude = altitude - in Chico, North/Polaris = 40 degrees |
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Azimuth
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- how far an object is away from North
- in degrees East = 90 South = 180 West = 270 North = 0 |
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Zenith
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point directly overhead
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Meridian
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the semicircle passing through North, the Zenith, and South
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Constellation
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- group of stars connected by dashed lines
- region of the sky with well-defined borders - named by Sumerians - 88 constellations are recognized |
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Circumpolar Constellations
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- stars close to the N and S poles that remain perpetually above horizon
- never rise and set - make daily counterclockwise circles |
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Asterism
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- group of stars within a constellation
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Zodiac
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- 12 constellations along the ecliptic
- 30 degrees wide and 16 tall - we don't see certain zodiacs during the year because the sun is in the way of them |
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Bayer Letters
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- measures the brightness of a star
- alpha, beta, gamma, delta - brightest to faintest |
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Siderial Day
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- how long it takes for a star to make a full circle through the sky
- 23 hours and 56 minutes - 1 degree short of a 360 degree rotation |
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Solar Day
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How long it takes for the sun to make it's circle
- 24 hours - 4 minutes longer than Siderial day - 361 degrees rotation - 15 degrees/ hour |
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Difference between Earth's rotation and revolution:
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Rotation
- full circle of earth on its axis - 24 hrs and 360 degrees (1 day) Revolution - full circle of Earth around the Sun - 365 days and 360 degrees (1 year) - 1 degree/ day |
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Astronomical Unit
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the distance between the earth and the sun
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heliocentric model
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sun at center of universe
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Kepler's 2nd law
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planets move slowest when farthest from the sun
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approx angular diameter of sun
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0.5 degrees
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the sun moves...
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west to east
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Ptolemaic model of solar system
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the sun orbits the earth on a circular orbit
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occam's razor
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the simplest solution is usually the correct one
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Aristotle's proofs to prove Earth is sperical
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1) observed lunar eclipses and noticed shadow on moon was curved
2) person on dock's horizon remained consntant while the sailor's remained the same 3) african vs. indian elephants |
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Hipparchus
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- correctly calculated the length of a year
-invented magnitude scale -used systematic observation -compiled research previous to him |
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Aristotle
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- gave 4 proofs for the earth being spherical
- Earth can't be moving -Geocentrism |
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Aristarchus
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- moon orbits earth
- calculated size and distance of sun, moon, and earth (all off) |
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Hipparchus
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- invented trig
- systematic observation - used past observations - discovered procession - made star catalogue - calculated distance to the moon correctly - calculated length of a year incorrectly - discovered the eccentric |
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Thales
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- 1st astronomer
- calculated length of a year - discovered ecliptic |
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Pythagoras
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- cosmos are perfect
- earth is imperfect |
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anaxagoras
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- discovered phases of moon
- discovered moon orbits the earth - calculated the distance and size of the earth incorrectly b/c he thought the world flat |
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Eratosthenes
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- calculated size of earth
- said it was round |
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ptolemy
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- geocentric = coined phrase
- discovered retrograde motion |
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Copernicus
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- discovered heliocentric model
- discovered exterior planets - coined "siderial" and "synodic" |
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Kepler
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- Kepler's 3 laws
- discovered orbits are ellipses - discovered Earth always has the same orbit |
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Galileo
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- perfected the telescope
- Discovered Jupiter's moons, Venus' phases, sunspots, and lunar topography - proved cosmos were imperfect |
