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Cosmic Fireworks: Supernova Explosions

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Cosmic Fireworks: Supernova Explosions

  1. 1. Dr. Stephen C. Y. Ng Department of Physics 超新星
  2. 2. Outline  Why study supernova?  What is a supernova?  Why does it explode?  The aftermaths --- Supernova remnants  Will it destroy the Earth?
  3. 3. Where do they come from?
  4. 4. Mines?
  5. 5. Supernova Explosions!
  6. 6. Supernova Explosions!
  7. 7. Gold, Silver & More
  8. 8. Heavy Elements
  9. 9. Building Blocks of Life
  10. 10. Life from Exploding Stars! Without supernovae to disperse elements made in stars, no planets, no life!!
  11. 11. Why Study Supernova?  They are cool  most powerful explosions in the Universe 1017J 1044J1,000,000,000,000,000,000,000,000,000 =
  12. 12. Why Study Supernova?  They are important  produce heavy elements beyond iron, e.g. gold, silver,…  recycle materials into space, e.g carbon, oxygen,…  shock wave triggers new star formation  They can get you a Nobel prize  SN Type Ia as standard candles for cosmology  They are bombs  shock wave physics  They are cool  most powerful explosions in the Universe
  13. 13. What is a Supernova?  Nova 新星 = new star Supernova 超新星  Naming:  SN 2013A,…, SN2013Z, SN 2013aa,… SN 2013ab,…, SN 2013ej,…  Death of a star, most powerful explosion:  1027 nuclear bombs  brighter than a galaxy (~1011 stars)  more energy than the entire lifetime of a star SN 1994D
  14. 14. Historical Classification SN no H H Si no Si He no He Type Ia Type Ib Type Ic Type II
  15. 15. Physical Classification Thermonuclear Core Collapse SN no H H Si no Si He no He Type Ia Type Ib Type Ic Type II
  16. 16. Why do they explode?  Stellar evolution  Core collapse  Thermonuclear
  17. 17. Life of a Sun-like Star Protostars White Dwarf Planetary Nebula Red Giant Sun-like Star Star-Forming Nebula
  18. 18. Life of a Massive Star Protostars Black Hole SUPERNOVA Red Supergiant Massive Star Star-Forming Nebula Neutron Star
  19. 19. self gravity Pressure Balance
  20. 20. self gravity 2,000,000,000x in 1 second! Pressure Balance
  21. 21. self gravity gas pressure Pressure Balance
  22. 22. Stellar Alchemy
  23. 23. Life of a Sun-like Star Protostars White Dwarf Planetary Nebula Red Giant Sun-like Star Star-Forming Nebula
  24. 24. Massive Stars
  25. 25. Stellar Onion
  26. 26. Inert Iron Core
  27. 27. Stellar Onion not to scale
  28. 28. self gravity gas pressure Core Collapse
  29. 29. nuclear force Core Bounce
  30. 30. Core Bounce energy: 1046J 99% neutrinos 1% kinetic energy 0.01% visible light produce heavy elements recycle light elements triggers new star formation
  31. 31. Compact Core
  32. 32. Physical Classification Thermonuclear Core Collapse SN no H H Si no Si He no He Type Ia Type Ib Type Ic Type II
  33. 33. How about SN Type Ia?
  34. 34. White Dwarf Main Ingredient: White Dwarf
  35. 35. Mass Transfer
  36. 36. Accreting White Dwarf
  37. 37. Standard Candles
  38. 38. Standard Candles
  39. 39. When can I see a Supernova? • Expect 1–2/century in our Galaxy, but long overdue:  Cassiopeia A (~1680AD): peak magnitude = 6? too faint to see  G1.9+0.3 (~1868AD): not visible on Earth, too far and obscured
  40. 40. SN 1054 • 1054AD July 4 • Crab Nebula (Messier 1)
  41. 41. Crab Nebula • Remnant of SN1054 • Harbors the Crab Pulsar --- most energetic neutron star found in the Milky Way
  42. 42. Historical Supernovae Tycho’s SN •1572AD November •as bright as Venus •visible until 1574 SN 1006 •1006AD May 1 •brightest SN observed •visible for ~18months Kepler’s SN •1604AD October 9 •visible in day time for 3 weeks
  43. 43. Can I See One Now? • Catch one in the act? Go extragalactic! • As of today, 6000+ extragalactic SNe observed
  44. 44. Extragalactic SNe SN 2004et in NGC 6946SN 1994D in NGC 4526
  45. 45. SN 2013ej in M74 Taken here in HKU
  46. 46. SN 1987A
  47. 47. SN 1987A • 1987 Feb 23, in the Large Magellanic Cloud • closest (hence brightest) SN observed in 300 yr, since invention of modern telescope • ~11 neutrinos detected, 3 hr prior to visible light • complex environment Milky Way LMC SMC
  48. 48. Observations Australia Telescope Compact Array Chandra X-ray Observatory Optical X-ray Radio
  49. 49. Evolution
  50. 50. Expansion 35,000 km/s 4000 km/s
  51. 51. Next Supernova in Our Galaxy  A major event will be observed by every telescopes in all wavelengths  radio, IR, optical, X-ray, -ray,...  Multimessenger astronomy beyond EM radiation  neutrino telescopes  gravitational wave detectors
  52. 52. ~100,000 light years across Artist’s Conception of our Milky Way Galaxy Will it destroy the Earth? location of our solar system Nearest candidate (IK Pegasi): over 150 light years away! Supernova: within 30 light years
  53. 53. Summary  Supernovae are important:  produce everything on Earth  Explosion mechanisms:  core collapse of massive stars  thermonuclear detonations of white dwarfs  The next supernova?  we are safe
  54. 54. SNR G292.2-0.5
  55. 55. Triple-ring Structure
  56. 56. Triple Ring Nebula Morris & Podsiadlowski (2007)

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