Naked eye astronomy

Naked eye astronomy

1. Orbit

   • Direction that the sun...
     • -...moon and stars travel across the sky is east to west
   • Lengths of orbit
     • -Solar day = 24 hours -Sidereel day = 23 hours 56 minutes -Time take for the moon to appear in the same position = 24 hours 50 minutes
   • Sidereal days
     • -Sidereal day = the time it takes for the earth to rotate exactly 360 degrees -Time it takes for the stars to re-appear in the same place in the sky
     • SR vs. Solar?
       • -Solar takes longer because the earth spins and orbits, meaning it takes an extra four minutes to turn enough to face the sun in the same position again

2. Phases of the moon

   • Distance from earth
     • -384000 km
   • Lunar month
     • Time it takes the moon to orbit the Earth -29.5 days
   • As it orbits...
     • -Going from left to right (anticlockwise), the light comes from the right hand side -Going from right to left, the dark comes from the right hand side

3. Eclipses

   • When
     • -Occurs when the moon, earth and sun are directly in line -Solar eclipse = the moon is in the way of the earth -Lunar eclipse = the earth is in front of the moon
   • Pen/umbras
     • -Penubra = the area that is in total shadow -Umbra = the area that is in partial shadow
   • Occurrences
     • -Doesn't happen that often as the moon orbits on a different plane to the Earth -2-3 times a year

4. Naked eye planets

   • Easy
     • -Mercury Venus and mars can be seen -Closest three to earth
   • Hard
     • -Jupiter and Saturn -Far away but are huge so can also be seen

5. Retrogade motion

   • What?
     • -When planets appear to double back on themselves against the fixed backdrop of distant stars -Because we overtake/undertake them
   • Different speeds
     • -Planets closer to the sun complete their orbits more quickly than those further away
   • Explanation
     • -e.g. = earth and mars -When on opposite sides of the sun, we are travelling in opposite directions so mars looks further away -We catch up so it looks closer -We undertake it so it looks like it goes back on itself -It then evens back out as we move apart

6. Finding stars

   • Pole star
     • -The pole star is seen above the north pole -It can be seen all year around
   • Different parts
     • -The parts of the universe we see change as we orbit the sun -In winter, we look out on an opposite side to when we're in summer
   • Coordinates
     • Declination
       • -How far a space object is above/below the equator -90 degrees = above the North Pole -0 degrees = above the equator -South of the equator = negative declination
       • The angle of declination
         • -The angle made between a space object and the celestial equator 
         • Units
           • -Degrees, minutes, seconds
     • Right-ascencion
       • -How far east/west to look
       • The angle of right ascension
         • -Measured from the point where the sun enters the northern hemisphere
         • On a diagram
           • -Can be seen as the point where the ecliptic (a circle around the earth which describes the path the sun takes in our sky over the course of the year) crosses the equator -This is also when the spring equinox happens
         • Units
           • -Hours, minutes, seconds -The Earth turns 360 degrees in 24 hours, so 1 'hour' = 15 degrees
     • Use
       • -These two can be used to communicate the location of a space object
     • The celestial sphere
       • -An imaginary dome that surrounds the Earth  -Used for coordinates