1. For Wednesday, Feb. 4 Reading: Section 2.6 Assignments: Mini-Project #1 (due today) Homework #1 (due today) Mini-Project #2 (due Wed. Feb. 11) QUIZ #1 FRIDAY FEB. 6 PLANETARIUM SHOWS: Tues. Feb. 3: NOON, 1 PM Wed. Feb. 4: NOON, 1 PM, 3 PM Thur. Feb. 5: NOON ROOFTOP TELESCOPE VIEWING (Tues. 7 pm; PA Building) Mon. Feb. 9: 3 PM Tues. Feb. 10: 1 PM, 3 PM Wed. Feb. 11: 1 PM

2. The Moon and Orbits What can we learn about how orbits work by carefully observing Moon’s behavior? direction of Moon’s motion time to orbit (“period”) shape of orbit (“eccentricity”) tilt of orbit (“inclination”) VIEW FROM ABOVE NORTH POLE MOON EARTH SUNLIGHT

3. Reflecting Light Searches for planets around other stars: Moon phases: (IMAGINARY VIEW FROM EARTH) How bright is the Moon going to be? Is the Moon going to interfere with observations? When is it best to try to detect an extrasolar planet?

4. Thought Question: What would the Moon’s phase look like from the northern hemisphere of Earth (the part facing you in the figure)? YOUR VIEW: ABCD

5. Moon Phases As Moon orbits Earth, we see different amounts of lit and dark Moon… STEPS: 1.What direction is sunlight coming from? 2.What side of Moon is lit? 3.What part of lit side is visible to you? VIEW FROM ABOVE NORTH POLE MOON EARTH SUNLIGHT

7. The Phases about 1 week for each quarter (like new  first quarter)

8. Moon Phases VIEW FROM ABOVE NORTH POLE LESS THAN HALF FULL (CRESCENT) EARTH MORE THAN HALF FULL (GIBBOUS) GETTING MORE FULL (WAXING) EARTH GETTING LESS FULL (WANING)

9. Thought Question: The diagram below shows Earth and the Sun as well as 5 different possible positions of the Moon. Which of the positions best corresponds to the phase of the Moon in shown in the box? A. B. C. D. E.

10. Thought Question: If the Moon moves around its orbit as shown below, what will happen? A. It will rise earlier night after night. B. It will rise later night after night. C. It will rise at the same time night after night.

11. Directions in the Solar System All of these… Earth rotation (and most other planet spins) Moon’s orbit of Earth (and most other moon orbits) all planet orbits around Sun have counterclockwise direction as seen from above Earth’s N pole …came from spin of gas cloud that formed the solar system! …CONSERVATION OF ANGULAR MOMENTUM SUN MOON

12. Sidereal and Synodic Months SUN synodic month: time for Moon to make one circle of sky compared to Sun sidereal month: time for Moon to make one circle of sky compared to stars SUN Which type of month corresponds to exactly one Moon orbit? Which type of month corresponds to one cycle of Moon phases? 27.3 d29.5 d

13. Angular speed of Moon to east (relative to stars): Angular speed of Moon to east (relative to the Sun): Moon rises later by Rising Later… Moon moves from W to E around celestial sphere

14. Moon Rise and Set Imagine your head in Earth’s place: Is your head turned in the correct direction to see it? VIEW FROM ABOVE NORTH POLE MOON SUNLIGHT EARTH

15. Time of Day VIEW ABOVE N. POLE NOON (Sun high overhead) SUNSET (must look west to see Sun) SUNRISE (must look east to see Sun) MIDNIGHT (Sun on opposite side of Earth) SUNLIGHT ROTATION DIRECTION NP EastWest EW EW E W E W

16. Thought Question: If the Moon is positioned in its orbit as shown below, at what time would it be highest overhead? A. 9 am B. 3 pm C. 9 pm D. 3 am E. None of the above

17. Moonrise MOONRISE:  about 9 am (in this example)  about 6 hours before meridian VIEW FROM ABOVE NORTH POLE SUNLIGHT MOON HORIZON E W EWS VIEW FROM EARTH

18. Moonset MOONSET:  about 9 pm (in this example)  about 6 hours after meridian VIEW FROM ABOVE NORTH POLE MOON SUNLIGHTHORIZON E W EWS VIEW FROM EARTH

19. For Friday, Feb. 6 QUIZ #1 Assignments: Mini-Project #2 (due Wed. Feb. 11) PLANETARIUM SHOWS: Wed. Feb. 4: NOON, 1 PM, 3 PM Thur. Feb. 5: NOON Mon. Feb. 9: 3 PM Tues. Feb. 10: 1 PM, 3 PM Wed. Feb. 11: 1 PM

20. Solar Eclipses Video

21. The Moon and Orbits What can we learn about how orbits work by carefully observing Moon’s behavior? direction of Moon’s motion time to orbit (“period”) shape of orbit (“eccentricity”) tilt of orbit (“inclination”) VIEW FROM ABOVE NORTH POLE MOON EARTH SUNLIGHT

22. Thought Question: A total lunar eclipse just occurred. How long will it be before another lunar eclipse can occur? A.1/2 month B.1 month C.3 months D.6 months E.12 months

23. Orbits and Inclination Sun Orbits are flat (they can fit in a flat plane) BUT they are usually tilted relative to each other… inclination (i): angle between Earth’s and object’s orbit planes SIDE VIEW: Earth orbit Inclination i Moon orbit planet orbits are only inclined by a few degrees:

24. Tilt of Moon’s Orbit For an eclipse:  Moon must be new (solar eclipse) or full (lunar eclipse), AND  Moon must be crossing the ecliptic (near a “node”) Moon’s orbit is tilted 5º from ecliptic

25. Thought Question: How far can the Moon’s shadow miss Earth’s center? (Earth’s radius is 6380 km; Moon averages 384,400 km from Earth) Enter the number of Earth radii (rounded to the nearest whole number). to Sun  Moon’s umbra plane of Moon orbit Earth SIDE VIEW ? 5º5º

26. VIEWS FROM SUN: 3 Months later: eclipses possible Moon closest to Sun, but below Earth level Moon farthest from Sun, but above Earth level

27. Annular Eclipses Moon’s distance from Earth changes… 5 pictures superimposed

28. Angular Size angle A distance d size D If A is small, From Earth, Moon and Sun have nearly same angular size: the fraction of a circle the object covers

29. Thought Question Earth’s Moon can almost perfectly eclipse the Sun. Can Jupiter’s moon Ganymede totally eclipse the Sun as seen from Jupiter’s cloud tops? (Jupiter is about 5 times farther from the Sun than Earth is, Ganymede is about 50% larger than our Moon, and Ganymede’s orbit is about 3 times larger than Moon’s orbit.) A. Yes, total eclipses would happen even if Ganymede was the size of the Moon. B. Yes, total eclipses happen, but only because Ganymede is larger than the Moon. C. No, total eclipses do not happen

30. perigee (closest to Earth) apogee (farthest from Earth) Not a perfect circle!  ”eccentricity” Top View of Moon’s Orbit

31. perigee (closest to Earth) apogee (farthest from Earth)

32. Thought Question A)B)C)D) Draw the sun as a white circle, and the moon as a dark circle A B CD What would you see looking back toward the Sun?

33. Thought Question: A.A more-than-total eclipse B.An exactly total eclipse C.A less-than-total eclipse (annular) D.A partial eclipse. C What would things look like from “C”?

34. Shadows SIDE VIEWS: total shadow: UMBRA partial shadow: PENUMBRA lower edge of Sun blocked from view upper edge of Sun blocked from view

35. Thought Question A)B)C)D) Draw the sun as a white circle, and the moon as a dark circle A B CD What would you see looking back toward the Sun?