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Stellar Evolution

M<0.08 .08<M<0.4 0.4<M<1.4 1.4<M<~4 M>~4 P R O T O S T A R | M a i n S e q u e n c e

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Stellar Evolution

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  1. M<0.08 .08<M<0.4 0.4<M<1.4 1.4<M<~4 M>~4 P R O T O S T A R | M a i n S e q u e n c e | R E D G I A N T | | | Planetary Supernova | | | Nebula | | W h i t e D w a r f | B r o w n D w a rf Neutron Star OR Black Hole Stellar Evolution M A I N S E Q U E N C E R E D G I A N T W H I T E D W A R F B R O W N D W A R F

  2. Hubble image of gas and dust around a cluster of young, hot stars Fig. 12-1, p.248

  3. Protostar – contracting gas due to gravity. Size ~ 1 ly ~ 1013 km, energy source -- gravity. Main Sequence – normal star. Size ~ 106 km to 107 km, Energy – nuclear fusion 4H  He + energy. 0.7% of mass converted to energy, E = mc². Next stage – red giant. Size 100 times Main Sequence. If not enough mass then Brown Dwarf. Stellar Evolution

  4. Fig. 12-2a, p.248

  5. Main sequence stars Protostar Fig. 12-2b, p.248

  6. Fig. 12-4, p.250

  7. HST Protostar with two jets Fig. 12-5a, p.251

  8. Protostar with Jet Jet Fig. 12-5b, p.251

  9. Protostar with two jets Fig. 12-5c, p.251

  10. Mass of He is Less than 4 H. Difference gets Converted to Energy E = mc². Fig. 12-6, p.252

  11. Fig. 12-8, p.253

  12. Proton - proton chain fusion in main Sequence stars. Fig. 12-10, p.255

  13. Main Sequence stars. • The star is very stable and continues to produce energy until the • hydrogen in the core gets depleted and hydrogen to helium • fusion stops. • Energy source – Fusion of 4HHe + Energy • The energy production is directly proportional to ~ the mass to the • power 4 (M4). • Since the supply of energy is proportional to the mass, • then the lifetime of the star in the main sequence mode is • proportional to M/M4 = 1/M³. • The lifetime of a one solar mass star is 10 billion years (1010 yrs). • Other main sequence star lifetime in main is 1010/M³ years, • where M is in units of solar mass. • Since massive stars live a shorter lifetime, it is not surprising that • most of the main sequence star are low mass ones.

  14. Hydrostatic equilibrium in a main sequence star.

  15. Brown dwarf Brown dwarf Fig. 12-11b, p.256

  16. ν hardly interacts, so it escapes and reaches Earth with the velocity of light or in about 8 minutes. Since ν hardly interacts, ν detectors need to be extremely large. Solar neutrino problem pre 2000 – there are not enough neutrinos to account for the energy of the Sun. Problem solved, ν has a very small mass. Solar Neutrinos (ν)

  17. Homestake Solar neutrino Telescope South Dakota Fig. 12-12, p.256

  18. Water detector for Neutrinos in Japan. Kamiokande Fig. 12-13, p.257

  19. Sudbury Neutrino Observatory in Canada. Fig. 12-14, p.258

  20. Note: Planetary nebula are NOT related to planets. Fig. 12-15, p.258

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