1. Slide 1 Stellar Evolution 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 r f Neutron Star OR Black Hole 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. Slide 2Fig. 12-1, p.248 Hubble image of gas and dust around a cluster of young, hot stars

3. Slide 3 Stellar Evolution Protostar – contracting gas due to gravity. Size ~ 1 ly ~ 10 13 km, energy source -- gravity. Main Sequence – normal star. Size ~ 10 6 km to 10 7 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.

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

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

6. Slide 6Fig. 12-4, p.250

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

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

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

10. Slide 10Fig. 12-6, p.252 Mass of He is less than 4 H. Difference gets converted to energy E = mc².

11. Slide 11Fig. 12-8, p.253

12. Slide 12Fig. 12-10, p.255 Proton - proton chain fusion in main Sequence stars. Does not occur in one step. Also emit photon (γ) and neutrino (ν).

13. Slide 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 (M 4 ). 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 (fuel supply)/M 4 (fuel use) = 1/M³. The lifetime of a one solar mass star is 10 billion years (10 10 yrs). Other main sequence star lifetime in main is T = 10 10 /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. Slide 14 Hydrostatic equilibrium in a main sequence star. Gravity is balanced by outflow energy pressure

15. Slide 15Fig. 12-11b, p.256 Brown dwarf If protostar does not have enough mass to start nuclear fusion star contracts to Brown dwarf

16. Slide 16 Solar Neutrinos (ν) 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.

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

18. Slide 18Fig. 12-13, p.257 Kamiokande Water detector for neutrinos (ν) in Japan.

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

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