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Download Star Questions 2008 - Fort Thomas Independent Schools
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Astronomy Chapters 10-13 Star Questions: Evolution of Stars 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. How do stars form? What does it mean for a star to have a life cycle? Explain what it means for a star to be on the main sequence. Which two pressures act upon any star on the main sequence? Why a star remains roughly the same diameter when on the main sequence. Explain the following relationships: a. Surface temperature and color b. luminosity and mass c. absolute and apparent brightness What is the H-R Diagram? Describe the death of these two stars, one with 2 solar masses and one with 10 solar masses. What is a supernova and what is its significance? Describe the difference between a Type I and Type II supernova? What will happen to our Sun when it dies? Which is more luminous, a low-mass or a high-mass star? Explain. What is a neutron star? What is a black hole? What is the Chandrasekhar Limit? 1. How do stars form? See the Nebular Theory, chapter 5. Stars form from the dust and gases of a cold nebula. Compression event causes the matter to move and rotate, gravitational attraction causes the matter to clump, continued gravitational collapse increases the mass and temperature until a protostar develops. If greater than 0.08 solar masses, the temperature rises at the center of the protostar to 10 million K and initiates thermonuclear fusion of hydrogen into helium. 2. What does it mean for a star to have a life cycle? The star proceeds through stages of birth, life on the main sequence and death. 3. Explain what it means for a star to be on the main sequence. A star on the main sequence is fusing hydrogen into helium at its core. 4. Which two pressures act upon any star on the main sequence? Gravitational pressure (inward) and thermal pressure due to thermonuclear fusion (outward) 5. Why a star remains roughly the same diameter when on the main sequence. There is a balance of force between the gravitational pressure and thermal pressure. 6. Explain the following relationships: a. Surface temperature and color The color changes with the temperature of the star. Red stars are cooler than blue stars. b. luminosity and mass Luminosity and mass are directly proportional. As mass increases, so does luminosity. c. absolute and apparent brightness Absolute brightness or magnitude is the true brightness of the star as seen from 10 parsecs from the Earth, the apparent brightness or magnitude is the brightness of the star as seen from the Earth. 7. What is the H-R Diagram? A graph showing the relationship of star absolute magnitude, luminosity, color, spectral class and temperature. The main sequence stars are aligned at the center of the graph. Illustrates life cycle of stars. 8. Describe the death of these two stars, one with 2 solar masses and one with 10 solar masses. Two solar masses: red giant to white dwarf, quiet loss of gases produce a nebula. 10 solar masses: red supergiant to supernova to either a neutron star or black hole. 9. What is a supernova and what is its significance? A core collapse of a supermassive star or a star that has a core mass that exceeds 1.4 solar masses that produces an extreme explosion and fuses all heavy elements observed in the universe. 10. Describe the difference between a Type I and Type II supernova? Type I supernovae develop as the star accumulates more matter than it had when it was on the main sequence, causing the core to grow to a size greater than 1.4 solar masses. Type II supernovae occur when a supermassive star (> 8 solar masses) goes through core collapse and rebound, exploding violently. 11. What will happen to our Sun when it dies? It will expand (red giant), fuse helium at it core, slow release its gases and become a white dwarf (hot carbon core). Death will begin in 5 billion years. 12. Which is more luminous, a low-mass or a high-mass star? Explain. High mass stars are larger, so they emit more electromagnetic radiation or energy. 13. What is a neutron star? An extremely dense core of a large mass star (> 8 solar masses) that resulted from a supernova 14. What is a black hole? The result from a supermassive star that goes supernova, a black hole represents the total and utter unstoppable collapse of matter, gravity exceeds any degenerate pressure that could stop the collapse. 15. What is the Chandrasekhar Limit? The limit of mass in the core of a star that will not allow the star to go supernova. 1.4 solar masses