1. Lunar Phases Eclipses

2. Apparent motion: The Moon’s orbit: The phases of the Moon
Every object in the solar system is always
_____________________________________
If we sometimes see the bright side of an object, and sometimes see the dark side, then the object will appear to go through ___________
This is what causes the phases of the Moon
The Moon takes about 27.3 days to go once around the Earth - _________________
Because of Earth’s orbit the Moon takes 29.5 days to get back to the same place relative to the Sun - _________________
light on one side and dark on the other.
phases
Sidereal Period
Synodic Period (Lunar Month)

4. Sidereal vs. Synodic Periods
New
2.2 more days
New
27.3 days

5. The Moon Moon phases cycle over a period of 29.5 days
Always has the same “face” to Earth, which means it MUST _______
on its own axis!
Moon phases - result of the _______, _____, and __________ positions relative to each other
Moon rises later and later as the month goes on
________________
Plane of Moon’s orbit almost the same as Earth’s orbit - _______
rotate
Moon
Sun
Earth
50 min/day
5o tilt

6. Rises at 3 p.m.
Sets at 3 a.m.

7. Lunar Phases New Moon - ________________________________
___________________________________
Waxing Moon – ________________________
Waning Moon – ________________________
Full Moon - ________________________________
________________________________
Crescent – ________________________________
Gibbous – _______________________
The Moon is on the same part of the sky
as the Sun and rises and sets with the Sun
Increasing from day to day
Decreasing from day to day
The Moon is in the opposite side of the
sky as the Sun and rises when the Sun
sets and sets when the Sun rises
concave/convex edges, ending in a point
Rounded edges

8. Names/shapes of Moon phases (as seen from Northern Hemisphere)
First
_______
~1 week
______
Moon
~1 week
_______
Quarter
~1 week
_____
Moon
~1 week
______
Moon
_______
Crescent
Waxing
_______
_______
Gibbous
Waning
_______
New
Waxing
Full
Waning
Third
New
Quarter
Gibbous
Crescent
light “creeps” across Moon from ______________
darkness “creeps” across Moon from ________________
right to left
right to left

9. Phases of the Moon 1st Q. Wax. Gib. Wax. Cr. Full M. New M. Wan. Gib.
Sun’s
rays
Moon’s orbit
Wax. Gib.
Wax. Cr.
Earth N
Full M.
New M.
Wan. Gib.
Wan. Cr.
3rd Q.

10. The time the Moon rises and sets is correlated to its phase
Moonrise/Moonset
The time the Moon rises and sets is correlated to its phase
Phase of the Moon
Rise
Zenith
Set
New Moon
6 am
Noon
6 pm
Waxing Half Moon
Midnight
Full Moon
Waning Half Moon

11. Naming the Moon Blue Moon:
Definition One: The second of two full moons in a single month. It is uncommon since the cycle of phases of the moon is 29.5 days (synodic month) which is almost a month.
Definition Two: The third of four full moons occurring in a season. Again this is uncommon since the cycle of phases of the moon is 29.5 days and seasons are ~91 days (365/4=91.25).

12. Naming the Moon Harvest Moon:
The full moon that occurs closest to the autumnal equinox.
This results in the near full gibbous moons and the full moon lighting the fields for harvest for a longer period.

13. Eclipses

14. Eclipses
Eclipses occur when the Sun, the Earth and the Moon all lie along a straight line
They must line up in all 3 dimensions + time
the Moon’s orbit is tilted 5o with respect to the ecliptic, so there are only two times a year when the paths overlap

15. Eclipses Lunar Eclipse
Earth positioned between the Sun and the Moon and casts a shadow ______________
Much more common than a solar eclipse
Solar Eclipse
Moon positioned between the Earth and the Sun, casting a shadow _______________
During a total eclipse the Sun’s Corona, normally invisible is visible
Eclipses
onto the Moon
onto the Earth

16. Shadows ________ ____________ Umbra Penumbra
dark cone of complete shadow
____________
lighter area of partial shadow
Umbra
Penumbra

17. Apparent motion: The Moon’s orbit: Eclipses
When the Moon is in its Full Moon phase, it might pass through Earth’s shadow
When this happens it will be at least partially blocked from our view
This is known as a Lunar Eclipse
Three kinds of lunar eclipse (of interest to us):
Penumbral eclipse – _______________________
Partial eclipse - __________________________
Total eclipse – ___________________________
Moon in Earth’s Penumbra
Moon in part of Earth’s Umbra
Moon totally in Earth’s Umbra

19. Lunar Eclipses

20. Frequency of Lunar Eclipses
One might expect a lunar eclipse to occur every month during full moon
But the moon’s orbit is titled 5º to the Earth’s
For a lunar eclipse, the moon phase must be full and the moon must be aligned with Earth’s orbit (at a lunar node) – every 5-6 months
Partial eclipse – moon in penumbra where only some sunlight is blocked
Total eclipse – moon is located in the umbra where all of the sunlight is blocked

21. Apparent motion: The Moon’s orbit: Eclipses
When the Moon is in its New Moon phase, it might pass directly between us and the Sun
When this happens it will at least partially block the Sun from our view
This is known as a Solar Eclipses
Three kinds of solar eclipse:
Total eclipse – ___________________
Partial eclipse - _____________________
Annular eclipse – _____________________________
Total coverage
Moon not covering all Sun
Moon too far from Earth

23. Total Solar Eclipse of 21 June 2001 from Zimbabwe
Bailey’s Beads
See Richard Monk’s
webpage on eclipses:
astronomy/IAU_eclipses/
Solar Corona
“Diamond Ring”

24. Frequency of Solar Eclipses
Similar to a lunar eclipse, the Sun, Moon, and Earth, must all be aligned in the same plane
Much less frequent than lunar eclipses because the Moon is much smaller in size, and thus casts a much smaller shadow on Earth
Because the moon is on a slightly elliptical orbit, it may be too far to cast a shadow on the Earth

25. Future Solar Eclipses
If a solar eclipse occurs on a given day, another will occur in exactly 18 years and 11 1/3 days – saros cycle
But the eclipse may change type and location during that cycle

26. Upcoming Solar and Lunar Eclipses
Solar Eclipses:
Mar 20, 2015 (Total) – Europe, N/E Asia, W/W Africa, West in North America, Atlantic, Arctic
Sep 13, 2015 (Partial) – S in Africa, Atlantic, Indian Ocean
Mar8/9, 2016 (Total) – SE Asia, NE Australia, Pacific, Indian Ocean
Aug 21, 2017 (Total) – Much of North America
Lunar Eclipses:
Apr 4, 2015 (Partial) – Asia, Australia, Much of North Amer. and SA, Pacific, Atlantic, Indian Ocean, Arctic, Antarctica
Sep 28, 2015 (Total) – Europe SE Asia, Africa, Much of NA and SA, Pacific, Atlantic, Indian Ocean, Arctic, Antarctic
Mar 23, 2016 (Penumbral) Much Asia, Much NA and SA, Pacific, Atlantic, Indian Ocean, Arctic, Antarctic

27. Aug 21, 2017 (Total) – Much of North America

28. Motion of the Sun: Solar vs. Sidereal period
Since the Earth moves in its orbit each day, the motion of (nearby) solar system objects is slightly different from stars.
The Earth needs to revolve an additional 1 degree daily for the Sun to repeat its position (see diagram at right).
This takes an additional 4 min
This means that the Sun’s position repeats every 24 hrs. This is called the solar period.

29. Length of the Year
It takes the Earth days to go from one vernal equinox to the next
NOT an integer number
But the extra is close to ¼ = 0.25
So every 4 years (leap year) we add an extra day to the calendar (Feb. 29)
But this is too much (we’ve added 0.25!)
So every 100 years (on the century) we don’t add the extra day (no leap year)
But this isn’t right either, so every 4th 100 years, we do include the leap year
This is why 2000 was a leap year

30. www.hep.fsu.edu/~tadams/courses/ spr04/ast1002-2/Lecture011404.ppt