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  1. Get Involved at MCTC • MCTC Clubs – Get involved & meet people! • Science Club: Tue. Sep 30, 4-5pm, S1700 • Engineering Club: Fri. Oct. 3, 1pm, S1400 • Three-legged Frog Club (environmental): weekly on Thu., Oct. 2, 3:30-4:30pm, S2420 • MCTC Urban Farm Collective: free veggies Mondays 1-2pm T Bldg skyway; meeting Thursdays 4:20-5pm; help in garden Tu & Th 1-2:30pm, Wed 1-2pm & Fri 2:30-4pm • STEM Career and Internship Club: Oct. 2, 2pm • Friday Oct 10th, 12.45-2.00pm in S1400 • 100+internships available; get application in now • Scholarships for STEM majors – see me

  2. Today’s Comments • Observations • Planetarium due date change to DEC. 11 (previously Oct. 9) • Tuesdays, Fridays, Saturdays, Sundays on calendar • Moon Phases due Oct. 14 • 4 observations of the Moon (day or night) • Telescopes, Moon Craters & (possibly) Star Gazing due Dec. 11 • Fridays: 10/3, UMN Telescopes (weather not looking good) • Saturday, 10/4, Eagle Lake Observatory (Baylor): Fall Astronomy Day 2-10pm • Sunday, 10/5, Macalaster College • Moon Motion due Dec. 2

  3. Today’s Comments • Lab Schedule • Lab today, Oct. 2: North Circumpolar Constellations, Parallax and Precession • No lab Tuesday, Oct. 7 (emergency drill at 1:45pm) • Lab Thursday, Oct. 9: Dimensional Analysis and Significant Figures (print and bring calculator) • Lab Tuesday, Oct. 14: Dimensional Analysis and Significant Figures (print and bring calculator) • No lab Thursday, Oct. 16: Ed. MN Days • Lecture Schedule • Lecture on Oct. 7, 9 & 14 as usual • No lecture Thursday, Oct. 16: Ed. MN Days • No classes at MCTC Oct. 16 & 17

  4. Spectra Radiation and Spectra Three types of spectra What we can learn from spectra

  5. Electromagnetic (EM) Spectrum Visible ROY G. BIV  Long λ (700 nm) (400 nm) Short λ  Low f High f Low energy High energy <5% of universe Ralph's Mother Is Visiting Uncle Xavier's Garden Radio Microwave Infrared Visible Ultraviolet X-ray Gamma Part of the above from http://library.thinkquest.org/10380/advanced.shtml

  6. Electromagnetic (EM) Waves Go X-ray Uncle Vern’s Inside Middle Rib Gamma X-ray Ultraviolet Visible Infrared Microwave Radio Radar TV FM AM

  7. Which type of EM wave is generated from radioactive materials? GAMMA RAYS or gamma radiation Radar TV FM AM • Gamma rays are used in medical PET scans. • Most gamma rays are generated from universe.

  8. Which type of EM wave is used to look at human bones? X-RAYS Radar TV FM AM • X-rays are used in airport security. • X-rays are emitted from hot gases in the universe.

  9. Which type of EM wave causes sunburn, skin cancer, cataracts? ULTRAVIOLET Radar TV FM AM • From “hot” objects in space (Sun and stars)

  10. Which type of EM wave can you see? VISIBLE Radar TV FM AM • From fireflies, light bulbs and stars

  11. Which type of EM wave feels warm? INFRARED Radar TV FM AM • From our bodies and objects with heat • Used in TV remote controls and night vision goggles • Penetrates smoke and dust • Helps map dust between stars

  12. Which type of EM wave warms food? MICROWAVES Radar TV FM AM • Used to learn about the structure of nearby galaxies

  13. Which type of EM wave can you hear? RADIO Radar TV FM AM • Frequency of most wireless devices • From stars and gases

  14. Electromagnetic (EM) Waves < 5 % of universe Radar TV FM AM

  15. All EM waves: • Travel through the vacuum of space (sound cannot) • Travel at the speed of light through the vacuum of space

  16. All EM waves Differ in: • λ • f • Energy • Temperature

  17. Earth’s atmosphere absorbs most EM waves http://www.ipac.caltech.edu/outreach/Edu/Windows/irwindows.html

  18. Looking with “other eyes” Ex: Newborn stars (IR) Spectra DR21 6000 ly 75 ly Cygnus

  19. Visible Infrared Spectra

  20. Composite visible Near IR 938 nm 938 nm, 889 nm, 420 nm Green – surface Red – high atm, methane absorbs sunlight Blue – violet wavelengths for the haze Titan (moon of Saturn) – NASA/JPL

  21. To detect an extremely energetic event like two neutron stars merging, “look” for this kind of wave: 1. Radio 2. Micro 3. IR 4. Visible 5. UV 6. X-ray 7. Gamma

  22. To detect a very low energy event like the spin flip of a H atom, “look” for this kind of wave: 1. Radio 2. Micro 3. IR 4. Visible 5. UV 6. X-ray 7. Gamma

  23. Spectra **Waves carry energy, hence, information. λ (or color) tells you… Temperature Ex: Star color tells you hot star or cool star

  24. Spectra From last lecture: Spectrum – display of color or wavelengths Spectra – plural

  25. Wave Properties (Previous Lecture) 1. Speed 2. Wavelength 3. Frequency 4. Energy

  26. What can we learn from spectra? 1. Temperature - from color (last lecture) 2. 3. 4.

  27. What can we learn from spectra? 1. Temperature - from color (last lecture) https://docs.kde.org/stable/en/kdeedu/kstars/ai-colorandtemp.html

  28. What can we learn from spectra? 1. Temperature - from color (last lecture) 2. Composition - from spectra lines 3. 4.

  29. Spectra Diffraction Grating • Spreads out the wavelengths • Uses parallel lines to split and diffract light • Same spectrum on both sides • Ex: Show light bulb spectrum (handout)

  30. Three Types of Spectra Spectra Continuous Emission Absorption Combinations

  31. Types of Spectra Continuous, Emission, Absorption Describe: Spectra

  32. Types of Spectra Continuous, Emission, Absorption Describe: Rainbow like, all λ Spectra

  33. Types of Spectra Continuous, Emission, Absorption Describe: Rainbow like, all λ Source: Hot, dense object Spectra

  34. Types of Spectra Continuous, Emission, Absorption Describe: Rainbow like, all λ Source: Hot, dense object Ex: Filament of light bulb, surface of star Spectra

  35. Types of Spectra Continuous, Emission, Absorption Describe:

  36. Types of Spectra Continuous, Emission, Absorption Describe: Bright lines

  37. Types of Spectra Continuous, Emission, Absorption Describe: Bright lines Source:

  38. Types of Spectra Continuous, Emission, Absorption Describe: Bright lines Source: Excited gas Ex: gas tube gas clouds in space

  39. Emission Spectra Compare spectrum of H to He Spectra

  40. Emission Spectra Compare spectrum of H to He H spectrum is different than He spectrum Spectra

  41. Emission Spectra Each element has a unique spectrum. Different gases have different spectra. Now know composition of stars!!! Spectra

  42. Types of Spectra Continuous, Emission, Absorption Describe: Emission Absorption

  43. Types of Spectra Continuous, Emission, Absorption Describe: Missing colors Dark lines Missing λ Continuous with missing λ

  44. Types of Spectra Continuous, Emission, Absorption Describe: Dark lines Source:

  45. Types of Spectra Continuous, Emission, Absorption Describe: Dark lines Source: White light shining through a gas or liquid i.e. Light from a hot dense object shining through a gas or liquid

  46. What can we learn from spectra? • Temperature (from color) • Composition (from spectra lines) • Density (from type) = mass/volume • Continuous (rainbow) • Emission (bright lines) • Absorption (dark lines)

  47. Spectra http://www.jb.man.ac.uk/astronomy/nightsky/AList/Albireo.jpg What can we learn from EM spectra? • Temperature 2. 3. 4. Composition Density http://astro.unl.edu/naap/hr/hr_background1.html

  48. Hot Dense Object

  49. Hot Dense Object Same lines

  50. Spectrum of our sun What type of spectrum? What does that tell you about our sun? ABSORPTION SUN VIEWED THROUGH GAS CLOUD