1. http://www. cfht. hawaii. edu/HawaiianStarlight/monthlysequence-0904
Phys 1830: Lecture 4
Worried about the math?
-- OPUS (Organization of Physics Undergraduate Students) can tutor! Find them on the tunnel level of the Allen Physics Building.
-- Tutorial hour Today 3pm
-- Discussion Today 3:30 pm
-- Tutors available (talk to Dr. English)
- links on supplemental page
Previous Class:
Scientific Method
Angular Size
Linear measurements (ex. Diameter) Define distance units (AU)
Powers of Ten notation
This Class:
continue with Powers of 10
scale of solar system
ROLL CALL CLICKERS
ALL NOTES COPYRIGHT JAYANNE ENGLISH
The state of the affairs from the previous class is that we measure arcs on the sky.
If you want to learn math, check out
New to class? you need a password.
Next Classes:
Near Earth Objects
Definition of Parsec
Distance via Parallax
Distance via the Inverse Square Brightness Law
Light and Electromagnetic Radiation
The interaction between atoms and light
Add/Drop date WEDNESDAY
Today! Tutoring 3pm
Discussion 3:30pm

2. University of Manitoba Astronomy Club
Special Club!
Contact:
Wonder about the origins of the Universe? Curious about black holes? Come out and help design the club activities! No need to be a geek 
First Meeting Monday Sept 23 at 7pm in Allen 330

3. Set frequency of iclicker to base unit:
Set up iclickers:
TIP: Write down your iclicker number and save it somewhere safe.
iclicker marks for participation start on Monday. Answer 75% of questions in a particular class to get 1 mark for that class.
While waiting, talk about how you would define the edge of the solar system. How far away do you think that edge is?
Do NOT register iclickers online! We will register them in class.
Set frequency of iclicker to base unit:
Hold down power on/off button until it blinks.
Press B, then press B.
Bottom light should flash green.

4. I heard about astronomy courses at Info Days
a) true
b) false

5. Distances: Special Distances
The average distance between the Earth and the Sun:
Let’s look at special distances again.
(e.g. If the sun shut off, how long would it take for us to know?)
How long does it take light to travel from the Sun to the Earth?
1 AU = 8 light-minutes

6. Distances: Special Distances
Definition of light-year:
Written “ly”
The distance travelled by light in one year
1 ly = 10 trillion km
(trillion = 1 with 12 zeros after it)
The earth really orbits in a slight ellipse. So the AU is really the average distance between the earth and the sun.
Ok we are now into huge numbers! Before talking more about distances, let’s look at how we can handle the large numbers.

7. We will work with orders of magnitude
Powers of Ten Notation
We will work with orders of magnitude
Also check the supplemental website for computer interactives and videos about the power of 10.
Ray and Charles Eames Movie – Powers of Ten

8. Distances to Planets and Stars:
Parallax Effect:
Hold your thumb just in front of your nose.
Close your right eye while keeping your left eye open.
Note where your thumb is relative to the shapes above.
Switch eyes and note where your thumb is relative to the shapes above.
Let’s move on to distances and objects for which you can’t use radar.
You should see a large shift in the apparent position of your thumb. The “baseline” for this effect is the distance between your eyes.

9. Distances in the Solar System
Rough distances. Exercise for the student: Work out the light-hours or light-years for these distances – you will need the information on previous slides.
Kuiper Belt:
Debris from solar system formation
Contains dwarf planets larger than the dwarf planet Pluto
Oort Cloud:
Comets come from these distances

10. Planetary System Example:
Dan Foley
Illustration by Don Foley
Oort postulated that there was a cloud of solar system debris because of the highly inclined orbits of comets that came from large distances.
Asteroid Belt 0 – 5.2 AU (i.e. Jupiter’s orbit)
Kuiper Belt is thicker than the Asteroid Belt
Oort Cloud is spherical

11. Solar System Scales: FYI
At the moment the relevant columns are the semi-major axis and angular diameter.
(You won’t need to memorize this.)
If 1 step between Earth and Sun, then last classical planet is 30 steps away.

12. How do we define the edge of the solar system?
Termination Shock:
The thin, invisible boundary of the inner, solar wind region.
estimated between 80 – 100 AU (i.e. within the Kuiper Belt).
2. Heliosheath: solar wind is slow and turbulent.
3. Heliopause: Termination of the heliosphere.
Separates the solar material from the interstellar medium.
Estimated between 120 to 150 AU.
Interstellar Boundary Explore IBEX.
The influence of the solar wind ends beyond the Heliopause- between 120 & 150 AU.

13. Where is Voyager 1?
So in the Kuiper Belt! Not at the edge of the solar system defined by the Sun’s gravitational pull (outer edge of Oort cloud).
125 AU from Earth, and is expected to take roughly 300 years to reach the inner edge of the Oort Cloud and some years to escape it entirely.

14. Topics after powers of 10 : Electromagnetic Radiation
Wave and particle models of light
Colour and temperature
Interaction of light with matter
Spectra
Motion and Doppler Shift