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ASTR-1010 Planetary Astronomy

ASTR-1010 Planetary Astronomy. Day 11. Announcements. Read Chapter 4 Homework Chapter 4 will be due Thursday Oct. 7 Fri. Oct. 8 – last day to drop a class with a “W” 1 st Quarter observing sessions: Wed. Oct. 13 @ 7:00 pm Thur. Oct. 14 @ 7:00 pm Exam-2 – Thurs. Oct. 14

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ASTR-1010 Planetary Astronomy

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  1. ASTR-1010Planetary Astronomy Day 11

  2. Announcements Read Chapter 4 Homework Chapter 4 will be due Thursday Oct. 7 Fri. Oct. 8 – last day to drop a class with a “W” 1st Quarter observing sessions: Wed. Oct. 13 @ 7:00 pm Thur. Oct. 14 @ 7:00 pm Exam-2 – Thurs. Oct. 14 Mon. Nov. 8 – last day to drop with a “W” “F” or “FA”

  3. Each chemical element produces its own unique set of spectral lines when it is excited

  4. The type of spectrum given off depends on the objects involved Law #1 – The excited atoms within a hot dense object give off light of all colors (wavelengths) and produce a continuous spectrum -- a complete rainbow of colors (range of wavelengths) without any spectrallines.

  5. We will study three types of spectra!!! prism Hot/Dense Energy Source Continuous Spectrum

  6. The type of spectrum given off depends on the objects involved Law #2 – The excited atoms within a hot, cloud of gas give off only particular colors (wavelengths) of light and produce an emission line spectrum - a series of bright spectral lines against a dark background.

  7. We will study three types of spectra!!! prism Hot low density cloud of Gas Emission Line Spectrum

  8. The type of spectrum given off depends on the objects involved Law #3 – When the light from a hot dense object passes through a cool cloud of gas, the atoms within the cloud can absorb particular colors (wavelengths) of light and produce a absorption line spectrum - a series of dark spectral lines among the colors of the rainbow.

  9. We will study three types of spectra!!! prism Hot/Dense Energy Source Cooler low density cloud of Gas Absorption LineSpectrum

  10. We will study three types of spectra!!! prism Hot/Dense Energy Source Continuous Spectrum prism Hot low density cloud of Gas Emission Line Spectrum prism Hot/Dense Energy Source Cooler low density cloud of Gas Absorption LineSpectrum

  11. Tutorial:– p.63Light & Atoms • Read the instructions and questions carefully. • Discuss the concepts and your answers with one another. Take time to understand it now!!!! • Come to a consensus answer you both agree on. • If you get stuck or are not sure of your answer, ask another group. • Work with a partner! • 5 minutes

  12. ClassAction Stuff • 3 View spectrum animation • Blackbody demonstrator • Light & Filters

  13. All objects emit radiation.For objects of same size:- the peak intensity drops with temperature;- the wavelength of maximum intensity moves to the red (longer) with falling temperature.

  14. What physical situation does a star like the sun present? A hot dense core surrounded by a low density atmosphere. Why is this important in planetary astronomy? Planets reflect starlight.

  15. The Sun’s Spectrum

  16. When we look at a Planet • We see the Sun’s spectrum reflected by that planet (atmosphere and/or surface). • This is further modified by Earth’s atmosphere if we observe from the ground.

  17. The Doppler Effect • Definition:“The change in wavelength of radiation (light) due to the relative motion between the source and the observer along the line of sight.”

  18. Astronomers use the Doppler Effect to learn about the radial (along the line of sight) motions of stars, and other astronomical objects.

  19. Real Life Examples of Doppler Effect • Doppler Radar (for weather) • Airplane radar system • Submarine radar system • Ok, anything with radar • Radar gun, used by Law Enforcement

  20. Doppler Shifts • Redshift (to longer wavelengths): The source is moving awayfrom the observer • Blueshift (to shorter wavelengths): The source is moving towards the observer Dl = wavelength shift lo = wavelength if source is not moving v = velocity of source c = speed of light

  21. Doppler Effect • When the source of light is moving away from the observer the wavelength of the emitted light will appear to increase. We call this a “redshift”.

  22. Doppler Effect • When the source of light is moving towards the observer the wavelength of the emitted light will appear to decrease. We call this a “blueshift”.

  23. Doppler Effect • “Along the line of sight” means the Doppler Effect happens only if the object which is emitting light is moving towards you or away from you. • An object moving “side to side” or perpendicular, relative to your line of sight, will not experience a Doppler Effect.

  24. Doppler Effect • When something which is giving off light moves towards or away from you, the wavelength of the emitted light is changed or shifted V=0

  25. V=0 Astronomy Application

  26. Doppler Shift Lecture Tutorial pg. 73 • Do this one to learn more … it’s normally done in the stellar class, but has application s to planetary astronomy.

  27. ClassAction Stuff • Doppler Shift Animation • Radial Velocity demo • Splash page questions

  28. Ranking Tasks – Doppler Shift - ExampleOthers due Thursday, Oct. 7 at class time

  29. ClassAction Stuff • Splash page questions

  30. Telescopes & Instruments

  31. Telescopes Telescopes have three functions: • Gather light LGP ∝ Area = πR2 • Resolve objects Θ = 2.06 X 105 (λ/D) • Magnify EXTENDED objects

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