AST101 - Lecture 5: Ze Moon!

Moon

1. The same side of the moon is always facing the Earth when it revolves around it 

2. Only one half of the moon is

3. Orbits around once every 29.5 days (around once a month)  

4. Same plane as the orbit of the Earth around the Sun 

5. Orbit of the moon is tipped (5 degrees)  

   • Moon passes beneath and above the shadow  

   • This means there aren’t solar eclipse and lunar eclipse every Month 

6. Node/Eclipses 

   • The moon has two nodes

   • Orbit of the moon is tipped compared to the ecliptic in the right way  

   • Moon has the right part of the orbit and at the note for solar eclipse and lunar eclipses to occur

Lunar Eclpise

• Sun-Earth-Moon

• When the Earth blocks the moon 

• Happens when a full moons crossses the ecliptic plane 

• Can be seen from anywhere on Earth 

Solar Eclipse

• Sun-moon-earth

• When the moon blocks the sun 

• Moon goes in front between the sun and the Earth 

• Moon is blocking the sun and casting a small shadow on Earth  

• Happens when the New Moon crosses the ecliptic plane 

• Because the Moon’s orbit is tipped relative to the ecliptic plane, this happens rarely (every few years) 

• It only casts a shadow on a small part of the Earth

• Every 2-5 years

Full Eclipse

• When it exactly matches 

• Umbra: Where it perfectly blocks 

• Moon is 400x smaller than the sun but also 400x further away so it matches perfectly

• Every 2-5 years

Partial Eclipse

• When it doesn’t exactly match  

• Penumbra; When it nearly perfectly blocks

Annular Eclipse

• Moon passed directly between Eath and Sun  

• Does not completely cover the Sun’s disk

New Moon

• Sun aligned with the Eath, aligned with the Moon 

• Sun is a little bit above the moon (Can see like a small lsliver of the moon) 

• No solar eclipse 

• When the mon is in the direction of the sun 

• The only time a Solar eclipse can happen 

• Unlit side faces the Earth 

• Rises with the sun and sets with the sun 

• Not generally visible 

• Solar eclipses can only happen at a new moon

Waxing Crescent

• Getting bigger 

• Every day you see more and more light 

• 3-4 days after new moon 

• Rises 3 hours after the sun’ 

• Sets around 3 hours after the sun 

• Easiest to see right after sunset

First Quarter

• 1 week after the new moon 

• See half the moon 

• Quarter of the way around 

• Moon is Lit from the Side 

• Rises 6 hours after the Sun (Around noon) 

• Sets around midnight 

• Sets around 6 hours after the Sun 

• Easiest to see at night before midnight 

Waxing Gibbous

• 10-11 days after New Moon 

• More than half-full 

• Rises around 9 hours after the sun (afternoon) 

• Sets around 9 hours after the Sun 

Full Moon

• Sun, Earth, and the Moon are lined Up 

• No lunar eclipse unless it’s ligned up perfectly 

• Two weeks after new moon 

• Only time a lunar eclipse can happen 

• Rises around 12 hours after the Sun rises 

• Sets around 12 hours after the sun sets 

• Visible most of the night 

Third Quarter

 Around a week before the next new moon 

- Rises around 6 hours before sun rises 

- Sets round 6 hours before sun sets

Waning Crescent

• 2-4 days before next new moon 

• Rises around 3 hours before sun rises 

• Sets around 3 hours before sun Sets