1. The Study of the Sun
ES 24
Astronomy 2

2. The Study of Light
Astronomy 2
ES 24.1
Day

3. Opener – Quick Write
We are going to write for exactly one minute on a certain topic (to be shown once the bell rings).
You may do this in your notes.
On our opener for today, put “quick write”
Don’t pick up your pencils until I tell you to…
This is excellent practice for standardized tests (like the ACT/MME) The purpose is for you to get ideas out of your head and down on paper. Of course, it must be related to the question. See how many words you can get in 60 seconds! We will count them at the end.

4. Opener – Quick Write
Explain what the difference is between potential energy and kinetic energy, and how one can be converted to the other.

5. Light Light is very much still a mystery
Visible light is only a small part of all the different types of light
Electromagnetic Radiation: Includes gamma rays, X-rays, ultraviolet light, infrared rays, microwaves, radar waves, television/radio waves
All types of light travel at the same speed (300,000 km/s)

6. Electromagnetic Spectrum

7. Electromagnetic Spectrum

9. What is Light?
Light behaves in some ways like a wave and in some ways like a particle
Waves: think of waves in the water
Wavelength: the distance from one crest of a wave to the next
Different wavelengths = different colors
So violet and blue have very short wavelengths, red and orange have very long wavelengths

10. Opener How much of light can we see?
What other kinds of “light” are there? (name as many as you can remember)

11. Light as a Wave
Think of dropping a rock into a completely still pool of water…what happens?
Now think about at the beach, the breakwater…what happens to the waves?
The same thing happens with light
That’s why if a light is on in the hallway, it still partially lights up our room
Light “bends”

12. Photons Photons: streams of “light particles”
Because light sometimes acts like its made of particles instead of waves
Think of very small bullets fired from a machine gun…they have a force, they can push on matter
The force from light is called radiation pressure
Where did we hear that before???
Each photon has a specific amount of energy
Shorter wavelengths have more energy than longer wavelengths

13. The Doppler Effect
Doppler effect: the perceived change in wavelength from a source that is moving.
Sound: When an ambulance is approaching you, the siren sounds higher in pitch (because the waves are closer together)
Light: When an object is approaching, the light from it is appears redder than it actually is
Astronomy: Can determine whether stars are moving toward us or away from us

14. Brief Review Is light a wave or a particle?
How does light act like a wave?
How does light act like a particle?
What is the Doppler effect?

15. Tools for Studying Space
Astronomy (2)
ES 24.2
Day

16. Telescopes
Refracting Telescopes: uses a lens to bend light

17. Telescopes
Reflecting Telescopes: Uses a mirror to focus light in front of the mirror

18. Telescopes
Radio Telescopes: Focus incoming radio waves

19. Light Continued
Astronomy 2
ES 24?
Day ?

20. Opener
How does light act like a wave? Give an example (draw a picture if you want)
What are the particles of light that carry radiant energy called?

21. Reflection, refraction
Refraction: light bends through glass
Reflection: use of mirrors
When you shine a light at a mirror, what happens? What if its at an angle?
Angle of incidence = angle of reflection

22. Light and Telescopes What if you have a mirror that is curved?
Concave Convex
(light unites) (light diverges)

23. Concave/convex
Concave Convex
The front of a spoon The back of a spoon

24. Light
We can only see things because light is being reflected off of them
So when we see a blue object, its because the blue light is being reflected. All the other colors are being absorbed.
When waves pass into a different medium (substance), they change speeds
Why don’t they change wavelengths?
When light passes into a different medium (substance), it is refracted (bent).
Think of light going through water…it gets bent, distorted

25. Other electromagnetic waves
Sonar is using reflected sound waves underwater
Bats use echolocation (similar)
Know the general order of the different types of electromagnetic waves! We’ll be getting a worksheet on it…

26. Waves
Astronomy 2
PS 10
Day

27. Waves
Wave: Repeating movement that transfers energy through matter or space
So the wave travels only as long as it has energy to carry
Waves on a lake don’t actually move water…what do they move?
Think of a boat and a bunch of waves hit it, after they pass its in nearly the same place

28. Mechanical Waves
Transverse waves: matter moves at right angles to the energy (water, light, and electromagnetic waves)
Compressional waves: matter moves in same direction as energy (springs, and sound)

29. Parts of a wave Crest Trough Wavelength
Frequency: The # of wavelengths that pass by each second
1 Hz = 1 wavelength per second\
Amplitude: the height

30. Wavespeed v = fλ v = velocity (m/s) f = frequency (Hz)
λ = wavelength (m)
If we increase f, then λ must decrease
If we increase λ, then f must decrease
If the wave passes through a medium (substance) with different density, the speed may change

31. Wavelength
The lowest pitched sounds humans can hear have frequency of 20 Hz. What Is the wavelength of those sound waves if their speed is 340 m/s?

32. Wavelength
The speed of light is 300,000 m/s. Find the frequency of blue light (about 400 nm, or m) and of red light (about 800 nm, or m).

33. LAB – Retrograde Motion of Mars
Astronomy 2
Day

34. Opener
Suppose light is reflected from a surface and you decrease the angle of incidence by 0.5 (cut it in half). What will happen to the angle of reflection?
What color(s) wavelength is/are being reflected from a green book? What color(s) is/are being absorbed?

35. Retrograde Motion of Mars
Lots of graphing
To see how Mars moves in the night sky in relation to the stars
You may work in groups of 3 (your choice)
Use different colors!
Due: Monday (but you may turn it in today if you get done)

36. The Sun
Astronomy (2)
ES 24.3
Day

37. Opener Draw a quick sketch of a concave surface and a convex surface.
What effect does each surface have on light waves coming at it? (sketch it or use a one word answer)

38. The Sun’s Regions
Core
Photosphere
Corona
Chromosphere

39. Chromosphere Corona

40. Solar Wind
Solar wind: The streams of protons and electrons that shoot out from the sun’s corona
Sunspots: Dark regions on the photosphere

41. Aurora Borealis

42. Nuclear Fusion Nuclear Fusion: how the sun gives energy
During nuclear fusion, 4 hydrogen (H) atoms combine to form one helium (He) atom
4 H atoms have more mass than 1 He atom… so there’s leftover mass
E = mc2

43. The Sun’s Future The sun can “live” about 10 billion years
Its been around for 4.5 billion years
So it will be around for another 5.5 billion years
Sun changes
Sun formed
Now
4.5 billion years
5.5 billion years
10 billion years

44. Our Sun Our sun is a main-sequence star
We’ll learn more about this later…
In about 5.5 billion years, it will become a red giant
Don’t worry, we’ve got time!

45. Review Where does the sun’s energy come from?
What are sunspots? What is solar wind?
How long will the sun stay in its present form?

46. Waves Worksheet We’re going to do some of these in class
Some individually, some together
Then we’ll finish it as homework

47. Stars
Astronomy
ES 25
Day

48. Opener
Where does the sun’s energy come from (what is the process called?)
How much longer will the sun stay in its present form?
What is the difference between sunspots and solar wind?
5th and 6th hours: Your Mars Lab is due today! Please turn it in!

49. HW – Waves Worksheet Go over answers in your “natural groups of four”
The person who will read their answers for the rest of the group will be the person who….
We’ll go over any questions in a moment, but make sure you circle any that you don’t agree on!

50. Stars Nearest star: Proxima Centari – 4.2 light years away!
Stars are light years away!
1 light year = 9.5 trillion kilometers
Color relates to temperature…think of looking into a fire, what color is the middle of the fire? The outside?
Blue stars = very hot
Red stars = cooler

51. Betelgeuse and Rigel
Which is hotter???

52. Hertzsprung-Russell Diagram
The Hertzsprung-Russell diagram shows the relationship between absolute magnitude and temperature (of stars)
Shows dwarf stars, giants/supergiants, and main-sequence stars
About 90% of stars on HR diagram are main-sequence
Absolute magnitude: is bright
+10 is dim

53. HR Diagram

54. Some Questions for us… Which main-sequence stars are the brightest?
Which are the least bright?
Which are brighter, giants or dwarfs?
Where is the sun?

55. HR Diagram Lab Due Wednesday Plot carefully! Scales are not even!
Think about what your diagram should look like

56. Opener
Suppose you are looking at two stars, one is blue and one is red. Which one is hotter?
Where are most stars on the HR diagram (giant, dwarf, or main-sequence)?

57. Star death
All stars will eventually run out of fuel…then they collapse
Main sequence, dwarfs, and giants will all eventually “die”
This makes sense, if they’re using nuclear fusion (H to He) eventually they’ll run out of H!

58. Black Holes What do black holes look like???
Black holes: incredibly small, but EXTREMELY dense
They are old stars (used to be supergiants)
So they have a lot of mass in a little area
Remember more mass means more gravity, so these have a lot of gravity
Even light can’t escape the gravity of a black hole

59. Life, the Universe, and Everything
Galaxies: groups of stars, dust, and gases
What could hold them together??
Gravity!
Our sun is within one of the spiral arms of the Milky Way galaxy

60. Life, the Universe, and Everything
The Big Bang Theory says the Universe began 13.7 billion years ago with a violent explosion.
This would explain why the universe is expanding
Think of a balloon with a bunch of dots on the outside being blown up…the dots would continually separate from each other. Or think of baking raison bread, the same thing would happen.
Cosmic background radiation supports this theory
Cosmic waves are faint radio signals coming from every direction in space

61. Quick Review What will happen at the end of a stars life?
Where is our sun? (in which galaxy, and in what part?)
According to the big bang theory, how old is the universe?

62. Assignment Finish the worksheet/lab we started yesterday
Remember to use a ruler to help guide you!
Ask for help!!!
When you are done, there are a few questions about the diagram. You’ll need to refer to your notes for this.

63. Opener
Quick Write: Again, 60 seconds to spend on the following prompt. Do your best, compete against yourself! Try to beat your old score, but don’t sacrifice quality!
Also, reminder that our labs are due today! (on the HR diagram)

64. Opener
Prompt: Using definitions, examples, and/or analogies, compare transverse waves to compression waves.
Don’t forget the lab is due today! You can turn it in near the end of class.

65. Lab Questions
Are the nearest stars to us necessarily the brightest? How do we know?
Why did we not see any white dwarfs on our table?
Why is Betelguese so bright, when it’s a cool, distant star?

66. Review
1. Draw a quick sketch of an HR diagram, labeling the three groups of stars. Label each axis appropriately (you don’t need a scale)

67. Review
2. Briefly describe how the solar system formed (what did it start with, how did the process go)

68. Review
3. Draw the picture below, and put as many of the different types of electromagnetic waves as you can remember on it.
Short wavelength (λ)
Long wavelength (λ)

69. Review
You can spend the remainder of the time working on the review packet
Quiet atmosphere (working individually in your own seat, possibly checking your answers quietly with the person sitting next to you)
It will be collected on Friday, but don’t count on having time tomorrow to work!
Finish most of it tonight, then you have only a little more to do Thursday night.
Highlight/circle the ones you don’t know

70. Opener
What happens if you increase the frequency of a light wave? (What happens to the wavelength?)
What happens if you decrease the frequency?