ASTRcheatsheet1

ASTRcheatsheet1 - NOTES Proxima Centari nearest star (4.3...

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NOTES Proxima Centari – nearest star (4.3 LY) Celestial Sphere: coordinate system - right ascension (longitude; 0-360°) - declination (latitude; -90 - 90°) E axis tilt 23.5° Stars rotate E to W E rotates counterclockwise from above vantage pt E rotates clockwise from below vantage pt Polaris = star close to Northern Celestial Pole - At poles, all visible stars = circumpolar/never set - At Equator, no visible stars = circumpolar Circumpolar stars never rise or set Zenith =straight above you wherever you are Astronomical Time 1 Solar day (measured from meridian) = 24 hrs 1 Sidereal day = time stars to reach same pt in sky - 23 hrs 56 min Rotation vs. revolution E warmer in summer b/c tilted towards sun - Sunlight more direct - Length of day longer Precession – E axis of rotation changing direction - like spinning top (cycle = 26,000 years) - b/c E not spherical + force from sun/moon Lunar phase: half moon actually “Quarter moon” Synodic (Lunar) month – time it takes for moon complete all phases (full moon to next full moon) - 29.5 days Sidereal month – time it takes for moon to revolve 360°; 27.3 days Moon revolves at same rate as sidereal month -b/c tidal forces (“tidal locking”) Eclipses Lunar - sun, E, moon
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ASTRcheatsheet1 - NOTES Proxima Centari nearest star (4.3...

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