1. Jeff Hopkins Hopkins Phoenix Observatory (Counting Photons) Spectroscopy for Pre-Schoolers Member of SAC 2 October 2008

2. What is Light?

3. And There Was Light! Where: The divergence of E (electric field) = 0 The divergence of B (magnetic field)= 0 The curl of E = -partial derivative of B with respect to time The curl of B =  0 x  0 x partial derivative of E with respect to time In 1865 James Clerk Maxwell Said

4. These equations quite elegantly describe the relationship between electric and magnetic fields and thus electromagnetic radiation. What these equations describe is the unit of electromagnetic radiation called a photon. Maxwell’s Equations

5. Photons Light consists of small packets of energy called photons. Photons have no rest mass and always travel at the speed of light, since they are light. Depending on how a photon is measured it will manifest itself as a particle or wave. The frequency or wavelength of photon is a function of it’s energy. The higher the energy, the higher the frequency (shorter the wavelength).

6. Wavelength (  For Light  = c / f Where: is the wavelength in meters c is the velocity of light, 299,792,458 meters/second and f is the frequency in Hertz (Hz) For light frequencies, wavelengths are given in nanometers (nm) or Angstroms (Å). 1 nm = 10 Å

7. Energy verse Intensity To keep things straight, the intensity of light is related to the number of photons and the energy of light is related to the frequency or wavelength of the photons. The brighter a color, the more photons involved. The higher the energy, the more toward the blue end of the spectrum the photon is (higher frequency, shorter wavelength).

8. Photon Energy Where do photons come from? Atoms consist of a nucleus surrounded by electrons. The electrons are in specific energy states or levels. If an electron is raised to a higher energy state it will soon fall back to its lower state and emit a photon of energy equal to the difference in the two energy states. E = h * c / Where: E = Photon Energy h = Planck’s Constant C = Speed of Light = Wavelength h = 6.62606896 x 10 -34 J.s

9. Absorbing Energy A photon interacts with an orbital electron and raises it to a higher energy state. The electron absorbs the photon.

10. Emitting Energy After a short time the electron falls back to its lower energy state emitting a photon with the energy of the difference between the two energy states

11. Electromagnetic Spectrum The sensitivity of the human eye determines the visible spectrum and is typically 380 nm to 750 nm

12. What is Color?

13. Newton’s Experiment (1670) White light breaks up into colors Light colors combine to white light Single color does not change

14. RGB Photons Red, Green and Blue photons produce White for us to see.

15. There are no White Photons

16. Our Eye Our eye has sets of light cones that are sensitive to red, green and blue photons.

17. ColorColor Color is an illusion! Different intensities of different energy photons striking our eye produce all the colors we see. Sometimes our eyes fools us greatly.

18. Our Experiment Each of you will have your own spectroscope so you can examine light. This is yours to keep. It is a scientific instrument so treat it well! Do Not take it apart! Diffraction Grating Slit

19. Your Spectroscope Do Not take it apart!

20. What You See Adjusting If needed, hold the slit end with the slit vertical and rotate the tube to see the above. The spectral lines should be on the right and left.

21. White Light

22. White You should see Red Green and Blue Lines There are no White photons or lines.

23. Red Photons

24. Red Light

25. Red You should see a Red Line

26. Green Photons

27. Green Light

28. Green You should see a Green Line

29. Blue Photons

30. Blue Light

31. You should see a Blue Line

32. Yellow Light

33. Yellow You should see Red and Green Lines

34. COLOR IS AN ILLUSION

35. Red & Green Photons Red and Green photons produce Yellow for us to see.

36. Yellow Photons There are also Yellow photons as well as photons of every color.

37. Demonstration

38. Pickle Light A normal Pickle with power applied. intense yellow sodium D lines light are emitted

39. Incandescent Light A continuous Spectrum

40. Fluorescent Light A Emission Spectrum

41. Pickle Light Spectrum You should see a Yellow Line

42. RGBRGB Three basic colors of visible light are RGB. RGB stands for Red, Green and Blue Combinations of these colors with different intensities (number of photons) can produce all the colors we can see. RGB is an emission color set meaning color of the emitted light as opposed to reflected light. TV sets and computer monitors use emitted RGB light at different intensities to produce desired colors.

43. Why RGB While photons of the desired color could be used it would mean we would need to be able to generate millions of different colored photons for all the colors. Because our eye responds to RGB photons with the effect of letting us see any color by just varying the RGB intensities, we can generate all the colors with just the three RGB colored photons.

44. RGB (Single Colors) RedGreen Blue

45. RGB (Combinations) 100% Green + 100% Blue = Cyan100% Red + 100% Blue = Magenta 100% Red + 100% Green = Yellow

46. RGB (Extremes) 100% Red + 100% Green + 100% Blue = White 0% Red + 0% Green + 0% Blue = Black

47. TechnicolorTechnicolor Colors seen on a movie screen, TV screen or computer monitor are the results of a combination of three basic colors, red, green and blue. Color film is a combination of three layers (RGB) combined to produce a full color image. We can produce a full color image by take monochrome pictures through a red, green and blue filter and then shinning white light through each and overlapping them.

48. Taking Monochrome Images

49. Three Monochrome Images Scene through Red FilterScene through Green Filter Scene through Blue Filter

50. Red Filter Image

51. Green Filter Image

52. Blue Filter Image

53. CompositeComposite

54. CYMKCYMK When an object is illuminated with white light, it will reflect colors. The basic colors of reflection are CYMK. CYMK stands for Cyan, Yellow, Magenta and Black. The characteristic of the material determines what colors are reflected. CYMK is used to create color with ink and paints. It is a reflective color creating set of basic colors. Color pictures in magazines, and books use this. It is known as a four-color process. White light reflected from the paint or ink produces the colors we see.

55. CYMK Reflection White light reflected from the paint or ink produces the colors we see.

56. CYMK Colors Magenta YellowCyan 100% Cyan + 100% Magenta + 100% Yellow = Black

57. CYMK (Combinations) 0%Cyan+0%Magenta+0%Yellow+0%Black=White 100% Magenta + 100% Yellow =Red100% Cyan + 100% Yellow =Green 100% Cyan + 100% Magenta =Blue

58. Types of Spectra Continuous Spectra Emission Spectra Absorption Spectra

59. Continuous Spectrum Continuous spectra are produced from a high temperature source such as inside the Sun or an incandescent light bulb

60. Emission Spectrum Emission spectra are produced from a source with excited atoms of an element, e.g., an LED, or fluorescent light bulb or the Pickle Light

61. Absorption Spectrum Absorption spectra are produced from a source with a continuous spectrum and a gas between the source and observer that absorbs photons with the energy of the spectrum of the gas.The Sun’s atmosphere absorbs lines for the elements in it.

62. Solar Spectrum

63. Solar Spectrum (detail)

64. Sun Spectrum

65. Fluorescent Tube Spectrum

66. LED Spectrum

67. Hydrogen Spectrum H line 656.28 nm

68. Sodium D Lines The sodium D lines are at 588.9950 and 589.5924 nm Absorption Lines Emission Lines

69. Galaxy 1 Spectrum H Line 670 nm At rest H line 656.28 nm

70. Galaxy 2 Spectrum H Line 675 nm At rest H line 656.28 nm

71. Galaxy 3 Spectrum H Line 690 nm At rest H line 656.28 nm

72. Galaxy Spectrums Galaxy 1 H Line 670 nm Galaxy 2 H Line 675 nm Galaxy 3 H Line 690 nm

73. Doppler Shift v =  x c /  is the change in wavelength due to motion is the stationary wavelength v is the relative velocity c is the velocity in the medium (speed of light in a vacuum is 3 X 10 8 m/s) To get just a 1% change in the frequency of light, a star has to be moving 1,864 miles per second. For a blue light bulb to look red, it would have to be flying away from you at 3/4 of the speed of light.

74. Galaxy Doppler Shift v =  x c / Thus for the galaxies Galaxy 1:  = 670 nm - 656 nm = 14 nm Galaxy 2:  = 675 nm - 656 nm = 19 nm Galaxy 3:  = 690 nm - 656 nm = 34 nm Galaxy 1: v = 6.4 x 10 6 meter/sec or 3,974 miles per second Galaxy 2: v = 8.7 x 10 6 meter/sec or 5,403 miles per second Galaxy 3: v = 15.5 x 10 6 meter/sec or 9,656 miles per second

75. Spectroscopy Spectroscopy is the detailed measure of an electromagnetic spectrum. A device used to display and measure an astronomical optical spectrum is known as a spectrograph. This device may also go by the name of spectrometer, spectroscope and spectrum analyzer. These terms are sometimes interchanged.

76. Spectroscope A spectroscope may use either a prism or grating, but is used visually.

77. Spectrometer A spectrometer usually uses a prism or diffraction grating with an electronic or photographic detector.

78. Spectrograph A spectrograph uses a diffraction grating with an electronic or photographic detector.

79. Lhires III Spectrograph

80. Lhires Diagram

81. HPO Spectroscopy

82. Raw Spectrum No pretty rainbow because a monochrome camera was used. If the spectrum was in color it would be all red. The dark line near the middle is a hydrogen alpha absorption line.

83. Spectrum Profile By summing the ADU values of pixel columns a spectrum profile can be generated.

84. H  Line When a gas discharge tube containing hydrogen gas is excited by passing a current through it, the gas glows red. There are several spectral lines produced, but the most prominent is the hydrogen alpha (H) line at 6,562.8 Å. Most stars are made of mainly hydrogen so the H line provides an excellent reference line with which to explore details about a star’s spectrum. Why the interest in the H Line?

85. Star H  Lines Stars burn hydrogen and produce a continuous spectrum. Some stars produce a large H emission line superimposed on the continuum. This is seen as a bright line in the continuum. Some stars have an atmosphere of hydrogen gas that absorbs the H radiation and thus produces a hole or dark line in the continuum.

86. H  Line Detail Shifted toward the blueShifted toward the red

87. Be Stars Be stars are non- supergiant B-type stars whose spectra have, or had at some time, one or more Balmer lines in emission. The mystery of the "Be phenomenon" is that the emission, which is well understood to originate from a flattened circumstellar envelope or disk, can come and go episodically on time scales of days to decades.

88. Be Stars (continued) This has yet to be explained as a predictable consequence of stellar evolution theory, although many contributing factors have been discussed, including: * rapid rotation * radiation-driven winds * nonradial pulsation * flarelike magnetic activity * binary interaction Observations indicate that all Be stars are rotating rapidly, at up to 90% of the velocity at which gravitational force is balanced by centrifugal force at the star's equator (~400 km/s). In effect, material at the surface of the star is almost in orbit, so that only a slight additional force is necessary to move it into the circumstellar disk.

89. Be Stars H  Line Near 100% H Ring Emission Some Absorption of Star H Emission Lower H Emission Greater H Absorption

90. A Mysterious Star System

91. Auriga N

92. Epsilon Aurigae While Epsilon Aurigae is not a Be star it is a most interesting star system. It is an eclipsing binary system and has the longest known period of 27.1 years. It also has the longest known eclipse of nearly 2 years. The main star is an F supergiant with a diameter of 200 times that of the Sun, one of the largest stars known. The unknown companion has a diameter of 2,000 times that of the Sun. The companion has been likened to a round paving brick with a hole in it. The next eclipse starts next summer.

93. Epsilon Aurigae System

94. Epsilon Aurigae Timing

95. Epsilon Aurigae H Out-of eclipse H is most interesting

96. Things To Do Use your spectroscope to look at: Stars at night Street lights Different kinds of light in your home Fires Anything that glows Have Fun and Learn!

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98. The End