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“ Dead ” Stars

“ Dead ” Stars. Outline. Test 3 Wednesday Dead (?) Stars Review (?). Test 3. Review Spectroscopy (Wein, Stefan) and Doppler Shift The Sun (structure, fusion) Magnitude Parallax Interstellar Medium Stellar Evolution Dead Stars. More Precisely 12-1 The Cycle of Stellar Evolution.

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“ Dead ” Stars

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  1. 1

  2. 2

  3. “Dead” Stars 3

  4. Outline • Test 3 Wednesday • Dead (?) Stars • Review (?) 4

  5. Test 3 • Review Spectroscopy (Wein, Stefan) and Doppler Shift • The Sun (structure, fusion) • Magnitude • Parallax • Interstellar Medium • Stellar Evolution • Dead Stars 5

  6. More Precisely 12-1The Cycle of Stellar Evolution 6

  7. Supernovae • On-line images • Supernova in M 74 http://www.rochesterastronomy.org/sn2003/n628s2.jpg • Supernova in NGC 1448 http://members.optushome.com.au/edobosz/images/1448_sn.jpg • Supernova in NGC 3169 http://www.astrooptik.com/Bildergalerie/PolluxGallery/NGC3169.htm • Supernova in NGC 3190 http://www.astrooptik.com/Bildergalerie/PolluxGallery/NGC3190.htm • Supernova in NGC 5965 http://www.nordita.dk/~dahle/ngc5965_sub.gif • Supernova in NGC 918 http://antwrp.gsfc.nasa.gov/apod/ap091112.html 7

  8. Chapter 13 • What is left after a Supernova? 8

  9. Figure 12.21Supernova Remnants 9

  10. Figure 13.1Neutron Star - from a type II Supernova • typically ~20 km diameter • mass > Msun • thimbleful would weigh 108 tons • rotate very quickly • have very strong magnetic fields. 10

  11. Figure 13.2Pulsar Radiation • The first observed neutron star was a pulsar • Neutron stars rotate VERY quickly. 11

  12. Figure 13.3Pulsar Model • lighthouse model - if the beam sweeps past the Earth, we see a pulse. 12

  13. At a distance of 1 A.U., which would have the greatest gravitational force? A) A 1 solar mass main sequence star B) A 1 solar mass white dwarf C) A 1 solar mass neutron star D) They all have the same force. 13

  14. At a distance of 1 A.U., which would have the greatest gravitational force? A) A 1 solar mass main sequence star B) A 1 solar mass white dwarf C) A 1 solar mass neutron star D) They all have the same force. 14

  15. At the surface of the object, which would have the greatest gravitational force? A) A 1 solar mass main sequence star B) A 1 solar mass white dwarf C) A 1 solar mass neutron star D) They all have the same force. 15

  16. At the surface of the object, which would have the greatest gravitational force? A) A 1 solar mass main sequence star B) A 1 solar mass white dwarf C) A 1 solar mass neutron star D) They all have the same force. 16

  17. A neutron star cannot be more than 3 Msun. 17

  18. A neutron star cannot be more than 3 Msun. • Surface gravity will become so great that not even light can escape. (Escape velocity > c) 18

  19. A neutron star cannot be more than 3 Msun. • Surface gravity will become so great that not even light can escape. (Escape velocity > c) • Stars that began with > 25 Msun will probably become black holes. 19

  20. Black Holes • Can black holes be made of things other than neutron stars? • Any object of any mass has a radius that if it is compressed below that radius, light cannot escape. • This is called the Schwarzschild radius. • rS = 3km x M(solar masses) 20

  21. Black Holes • Example Schwarzschild radii : • Sun = 3km • 3MsolarCore = 9km • Jupiter = 3m 21

  22. Black Holes • Exercise - calculate the size required to compress a 70 kg person to make a black hole. • recall: rS = 3km x M(solar masses) 22

  23. Black Holes • Example Schwarzschild radii : • Sun = 3km • 3MsolarCore = 9km • Jupiter = 3m • Earth = ~1cm • Person = ~1x10-25 m • Mobservable universe = ~robservable universe 23

  24. If the Sun were suddenly replaced by a one solar mass black hole: A) we would immediately escape into deep space, driven out by its radiation. B) our clocks would all stop. C) life here would be unchanged. D) we would still orbit it in a period of one year. E) all terrestrial planets would fall in immediately. 24

  25. If the Sun were suddenly replaced by a one solar mass black hole: A) we would immediately escape into deep space, driven out by its radiation. B) our clocks would all stop. C) life here would be unchanged. D) we would still orbit it in a period of one year. E) all terrestrial planets would fall in immediately. 25

  26. Practice Problem • You observe a binary star system where the two stars are exactly the same temperature. The diameter of one star is 1.2 times the diameter of the second star. How many times more energy is emitted by the brighter star? 26

  27. Practice Problem • You observe a binary star system where the two stars are exactly the same temperature. The diameter of one star is 1.2 times the diameter of the second star. How many times more energy is emitted by the brighter star? A. 1.095x B. 1.2x C. 1.44x D. 2x 27

  28. Practice Problem • You observe a binary star system where the two stars are exactly the same size. One star is 5500 K. The other star is 6100 K. How many times more energy is emitted by the brighter star? 28

  29. Practice Problem • You observe a binary star system where the two stars are exactly the same size. One star is 5500 K. The other star is 6100 K. How many times more energy is emitted by the brighter star? A. 1.11x B. 1.23x C. 1.51x D. 600x 29

  30. Review Questions 30

  31. An ordinary star becomes a Red Giant when: A) A white dwarf companion star goes nova B) There is no Hydrogen remaining in the star C) Nutrino oscillations drive the outer layers D) The core becomes almost entirely Helium 31

  32. An ordinary star becomes a Red Giant when: A) A white dwarf companion star goes nova B) There is no Hydrogen remaining in the star C) Nutrino oscillations drive the outer layers D) The core becomes almost entirely Helium 32

  33. A main sequence star of 19 solar masses will eventually be a: A) A brown dwarf B) A white dwarf C) A type I supernova D) A type II supernova 33

  34. A main sequence star of 19 solar masses will eventually be a: A) A brown dwarf B) A white dwarf C) A type I supernova D) A type II supernova 34

  35. A supernova is observed with very little H in the spectrum. It is most likely a: A) type I B) type II C) type III D) not enough information 35

  36. A supernova is observed with very little H in the spectrum. It is most likely a: A) type I B) type II C) type III D) not enough information 36

  37. A source of light is approaching us at 3,000 km/s. All its waves are: A) Red shifted by 1% B) Blue shifted by 1% C) Not affected, as c is constant in all reference frames. D) Red shifted out of the visible into the infrared E) Blue shifted out of the visible into the ultraviolet 37

  38. A source of light is approaching us at 3,000 km/s. All its waves are: A) Red shifted by 1% B) Blue shifted by 1% C) Not affected, as c is constant in all reference frames. D) Red shifted out of the visible into the infrared E) Blue shifted out of the visible into the ultraviolet 38

  39. How could you determine the temperature of the photosphere of the Sun? A) only direct spacecraft measurement B) Newton’s Law C) Stefan’s Law D) Wein’s law 39

  40. How could you determine the temperature of the photosphere of the Sun? A) only direct spacecraft measurement B) Newton’s Law C) Stefan’s Law D) Wein’s law 40

  41. If a star has a parallax of 0.05”, then its distance must be A) 5 light years. B) 5 parsecs C) 20 light years. D) 20 parsecs. E) 200 parsecs 41

  42. If a star has a parallax of 0.05”, then its distance must be A) 5 light years. B) 5 parsecs C) 20 light years. D) 20 parsecs. E) 200 parsecs 42

  43. Assume your naked eye limiting magnitude is 4. With a 70mm diameter telescope (100x area of your pupil) which object would be barely visible? A) Seventh magnitude Titan, Saturn’s largest moon. B) Eighth magnitude Uranus. C) Ninth magnitude Barnard’s Star D) Eleventh magnitude Tethys, another Saturn moon E) Thirteenth magnitude Pluto 43

  44. Assume your naked eye limiting magnitude is 4. With a 70mm diameter telescope (100x area of your pupil) which object would be barely visible? A) Seventh magnitude Titan, Saturn’s largest moon. B) Eighth magnitude Uranus. C) Ninth magnitude Barnard’s Star D) Eleventh magnitude Tethys, another Saturn moon E) Thirteenth magnitude Pluto 44

  45. On the H-R diagram, red supergiants like Betelguese lie: A) top right B) top left C) about the middle D) lower left E) on the coolest portion of the main sequence 45

  46. On the H-R diagram, red supergiants like Betelguese lie: A) top right B) top left C) about the middle D) lower left E) on the coolest portion of the main sequence 46

  47. From inside out, which is the correct order? A) core, convective zone, radiative zone B) photosphere, radiative zone, corona C) radiative zone, convective zone, chromosphere D) core, chromosphere, photosphere E) convective zone, radiative zone, granulation 47

  48. From inside out, which is the correct order? A) core, convective zone, radiative zone B) photosphere, radiative zone, corona C) radiative zone, convective zone, chromosphere D) core, chromosphere, photosphere E) convective zone, radiative zone, granulation 48

  49. If Vega is apparent magnitude zero, and Deneb first magnitude, then A) Vega is about 100x brighter than Deneb.. B) Deneb is one magnitude brighter than Vega. C) Vega appears 2.5x brighter than Deneb. D) Deneb must be a main sequence star, and Vega a giant. E) Vega must be 2.5x more luminous than Deneb. 49

  50. If Vega is apparent magnitude zero, and Deneb first magnitude, then A) Vega is about 100x brighter than Deneb.. B) Deneb is one magnitude brighter than Vega. C) Vega appears 2.5x brighter than Deneb. D) Deneb must be a main sequence star, and Vega a giant. E) Vega must be 2.5x more luminous than Deneb. 50

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