Lunar Phases
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The Moon + Eclipses

Phases Depend onOrbital Position• Sun

When Will the Moon Rise?

Moon’sSidereal &Synodic Month• Orbital period =27.3 days =sidereal period• From new moonto new moon =29.5 days =synodic period =month

Sidereal and Solar Day• Earth rotates once with respectto the stars in one Sidereal Day• But Earth orbits the sun(revolves around)• So it must rotate a little extra topoint to the sun again for oneSolar Day• 4 minutes or 1 degree each day

When will thefirst quartera) Sunsetmoon rise?b) Sunrisec) Noond) Midnighte) Night time because the moon only comesout at night

Lunar Eclipse Movie• Fred Espenak•

Lunar Eclipse Geometry• Umbra is dark part of shadow - no sun• Penumbra is light part of shadow – part of sun showing

Lunar Eclipse Animation• Total Lunar Eclipse = Whole Moon in Umbra• Partial Lunar Eclipse = Part of Moon in Umbra• Penumbral Lunar Eclipse = Moon only in Penumbra

Time Lapse Partial Eclipses• Time lapse shows moon moves thru Earth’s shadow• Curved shadow: Aristotle concludes Earth is sphere

Total Lunar Eclipse• Moon moves its diameter in an hour• Through the earth’s umbra part of the shadow,~2.5X moon’s diameter =1.5 hours in totality

Red Moonin Totality• White light from thesun scattered in Earth’satmosphere• Blue scattered more sored gets through• Color depends onclouds, volcanoes etc.

Lunar Eclipse as Seenfrom Moon

SolarEclipsemovie• Fred Espenak’

Partial SolarEclipse• Most solar eclipses are partial andare not noticed• Except by photographers• Proper solar filters very important

Partial & TotalEclipses• First the moon covers partof the sun = Partial phases• When totality occurs it isabout as dark as a night litby a full moon• The stars come out• Lasts a few minutes• Path of totality ~ hundredkilometers in diameter

Solar Corona• Digital composite of 22 negatives -21Jun01 from Zambia• Composite 01Aug07 eclipse, Russia• Streamers and holes – magnetic fields

Prominences• Chromosphere isatmosphere of sun• Prominences are Earthsized condensations inthe Chromosphere

Moon atApogee &Perigee• Apogee= Far fromEarth• Perigee= Close toEarth

Annular Eclipse• When Moon is at apogee andappears smaller than the sun• Moon’s shadow doesn’t reach Earth

Eclipses Happen at Full &New Moons• Solar eclipses happen only when the Moon is New• Lunar Eclipses happen only when the Moon is Full

1 st Eclipse Season

2 nd Eclipse Season

Only at the Nodesof the Moon’s Orbit• Lunar orbit is tilted by 5 degrees• So not all new/full moons are eclipses• Eclipse season twice a year

Eclipse Seasons• = solar eclipses; = lunar eclipses• Eclipses happen when sun is at a node; ~twice a year

Precession of Moon’s Orbit• Line of nodes connects nodes = intersection of moon’sorbit and Earth’s orbit• Moon’s orbit precesses 360° in 18.6 years• So Eclipse Season starts 19 days earlier each year

NorthAmericanTotal SolarEclipses

Solar Eclipse 21Aug17

If there is a solar eclipse on 21Aug then:a. There could be a lunar eclipse on 28 Augb. There could be a lunar eclipse on 07 Augc. There could be a solar eclipse on 21 Octd. The moon was passing thru the penumbra ofthe Earth’s shadowe. The sun was at one node and the moon wasat the other node

Columbus Predicts Lunar Eclipse• 29 Feb 1504• Columbus was running out of food and the Jamaicannatives would not trade for trinkets so• He set up a meeting to coincide with the lunar eclipse

Saros Cycle• Saros cycle (19 eclipse years=223 synodicmonths) = 18years 11days and 8hours• After 3 Saros cycles= 54 yrs 1 month same eclipseoccurs

The Big Moon Illusion• Small Angle Formula• Angular Diameter in arc seconds/206265” =Linear Diameter / Distance

Inner Corona &Diamond Ring• Tenuous extremely hot outer atmosphere is called corona• Occasionally sun shines through lunar valley forming“Diamond Ring”

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