1. Bellwork 9/16
What is the difference between the Equatorial system of locating objects and the Azimuth/Altitude system?

2. Planisphere Practice:
What is the RA & Dec. of Arcturus? (near constellation Bootes)
RA: ~14hr 15min
Dec: ~+20⁰

3. Planisphere Practice:
What is the RA & Dec. of Betelgeuse? (in constellation Orion)
RA: ~6hrs
Dec: ~+8⁰

4. Planisphere Practice:
Set your planisphere to September 16th at 10:00pm. Name a constellation that is RISING.
Taurus
Perseus
Aries
Ect…

5. Planisphere Practice:
Set your planisphere to January 12th at 6:00pm. Name a constellation that is SETTING.
Sagitta
Cygnus
Capricornus
Ect…

6. Planisphere Practice:
Set your planisphere to October 15th at midnight.
Name a constellation that is close to its ZENITH.
 Zenith = bisecting line of the meridian…
SO divide your “window” in half horizontally and choose a constellation at that bisecting line
Cassiopeia, Perseus

7. Planisphere Practice:
Set your planisphere to March 20th at midnight.
Name a constellation that is close to its ZENITH.
 Zenith = bisecting line of the meridian…
SO divide your “window” in half horizontally and choose a constellation at that bisecting line
Ursa major

8. Bellwork 9/19

9. Coming Up… Today—Earth-Moon-Sun system
Wednesday—Stellar parallax (measuring distances to stars)
Monday (9/26)—Cosmic Calendar, some review time
Wednesday (9/28)—Unit 1 test

10. Bellwork 9/13

11. With a small group… Discuss the articles you read
What did you agree or disagree with?
What did you find interesting or confusing?
In your own mind…is space exploration worth the time and resources we spend? What evidence do you have to back up your claim?

12. Earth-Moon-Sun System
Two primary motions:
Rotation: turning or spinning of a body on its axis
Revolution: the motion of a body (such as a planet or moon) along a path around some point in space.
*Both the moon and the Earth rotate & revolve

13. Earth-Sun System
Earth’s revolution is NOT circular…

14. Earth-Sun System What causes the seasons?
The tilt of Earth’s axis toward and away from the sun as the planet revolves around the sun

15. Other Earth Motions… Precession
Very slow Earth movement
“wobbling top”
Direction in which Earth's axis points continually changes
Movement with the solar system in the direction of the star Vega
Revolution with the Sun around the galaxy
Movement with the galaxy within the universe

16. Precession of Earth

17. Earth-Moon system Moon Phases
The relative positions of the Sun, Earth, and Moon constantly change
Lunar phases are a consequence of the motion of the Moon and the sunlight that is reflected from its surface
It’s because of our perspective from Earth…what we can see at any given time…
This is NOT Earth’s shadow!

19. Lunar motions Moon's period of rotation about its axis and its revolution around Earth are the same
Causes the same lunar hemisphere to always face Earth
Synodic month
Cycle of the moon phases
Takes 29 1/2 days

20. “To obscure light from”
Eclipses
“To obscure light from”
Solar eclipse
Moon moves in a line directly between Earth and the Sun
Can only occur during the new-Moon phase
Lunar eclipse
Moon moves within the shadow of Earth
Only occurs during the full-Moon phase
**For any eclipse to take place, the Moon must be in the plane of the ecliptic at the time of new- or full-Moon **

21. Solar eclipse

22. Lunar eclipse

23. Modeling lab:

24. Why don’t we have an eclipse every month??
Because the Moon's orbit is inclined about 5 degrees to the plane of the ecliptic, during most of the times of new- and full-Moon the Moon is above or below the plane, and no eclipse can occur
The usual number of eclipses is four per year

25. Why does a Lunar Eclipse Appear Red?
If the Earth had no atmosphere, the moon would appear invisible
But, the reflected light from the moon travels through our atmosphere

26. Why does the moon appear red/orange sometimes?
Our atmosphere!
When the moon is closer to the horizon, the light it reflects must pass through more of the atmosphere
More atmosphere = longer wavelength