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HR Diagram

HR Diagram. Read Your Textbook: Foundations of Astronomy Chapter 9, 10 Homework Problems Chapter 9 Review Questions: 1, 4, 5, 7 Review Problems: 1-5 Web Inquiries: 1 Homework Problems Chapter 10 Review Questions: 1, 2, 4, 6-8 Review Problems: 1-4, 8 Web Inquiries: 2.

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HR Diagram

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  1. HR Diagram • Read Your Textbook: Foundations of Astronomy • Chapter 9, 10 • Homework Problems Chapter 9 • Review Questions: 1, 4, 5, 7 • Review Problems: 1-5 • Web Inquiries: 1 • Homework Problems Chapter 10 • Review Questions: 1, 2, 4, 6-8 • Review Problems: 1-4, 8 • Web Inquiries: 2

  2. Intrinsic Brightness vs Spectral TypeA.K.A. Luminosity vs Temperature • HR diagram

  3. Stars within 5 parsecs • HR diagram

  4. 100 Brightest Stars • HR diagram

  5. Luminosity Function

  6. Spectral Frequency

  7. Luminosity Classes CLASS DESCRIPTION I Supergiants II Bright giants III Giants IV Subgiants V Main-sequence stars/dwarfs

  8. Luminosity Classes

  9. Spectral Luminosity Class SURFACE TEMPERATURE (K) LUMINOSITY (Lsun) RADIUS (Rsun) OBJECT 4000 0.1 0.7 K7 V MS 4000 20 10 K7 III giant 4000 3000 100 K7 I supergiant

  10. Main Sequence Masses

  11. Using The HR Diagram • Example 1: Spectroscopic Parallax • Same Spectral Type • means same temperature • Same Luminosity Class • means same size • m-M = 5 log d - 5 • Determine Distance by observing (m ), and utilizing the HR diagram to assume (M ). L/Lsun O B A F G K M

  12. Using The HR Diagram L/Lsun • Example 2: Size Determination • Same Spectral Type • means same temperature • Different Luminosity Class • means different size L = 4pR2sT4 M = 0, Msun = 5 O B A F G K M

  13. Using The HR Diagram L/Lsun • Example 2: Size Determination • Same Spectral Type • means same temperature • Different Luminosity Class • means different size L = 4pR2sT4 M = 0, Msun = 5 A difference in 5 magnitudes is 100x in brightness 4pR2sT4 = 100 4pRsun2sT4 R2 = 100 Rsun2 O B A F G K M

  14. Using The HR Diagram L/Lsun • Example 2: Size Determination • Same Spectral Type • means same temperature • Different Luminosity Class • means different size L = 4pR2sT4 M = 0, Msun = 5 A difference in 5 magnitudes is 100x in brightness 4pR2sT4 = 100 4pRsun2sT4 R2 = 100 Rsun2 Therefore, R/Rsun = (100)1/2 O B A F G K M

  15. Fundamental Stellar Parameters

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