Slide 1

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

| 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 ER 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

Slide 2 Fig. 12-1, p.248

Hubble image of gas and dust around a cluster of young, hot stars

Slide 3

Stellar Evolution

• 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 fusion4H 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.

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

Slide 5 Fig. 12-2b, p.248

Protostar Main sequence stars

Slide 6 Fig. 12-4, p.250

Slide 7 Fig. 12-5a, p.251

HST Protostar with two jets

Slide 8 Fig. 12-5b, p.251

Protostar with Jet

Jet

Slide 9 Fig. 12-5c, p.251

Protostar with two jets

Slide 10 Fig. 12-6, p.252

Mass of He isless than 4 H.Difference getsconverted toenergy E = mc².

Slide 11 Fig. 12-8, p.253

Slide 12 Fig. 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).

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 4HHe + 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 (fuel supply)/M4 (fuel use) = 1/M³. •The lifetime of a one solar mass star is 10 billion years (1010 yrs). •Other main sequence star lifetime in main is T = 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.

Slide 14

Hydrostaticequilibrium in a mainsequence star.

Gravity isbalanced byoutflow energypressure

Slide 15 Fig. 12-11b, p.256

Brown dwarf

Brown dwarf

If protostar doesnot have enoughmass to startnuclear fusionstar contracts toBrown dwarf

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.

Slide 17 Fig. 12-12, p.256

HomestakeSolar neutrinoTelescopeSouth Dakota

Slide 18 Fig. 12-13, p.257

Kamiokande

Water detector for neutrinos (ν) inJapan.

Slide 19 Fig. 12-14, p.258

Sudbury

Neutrino

Observatory

in Canada.

Slide 20 Fig. 12-15, p.258

Note: Planetarynebula are NOTrelated to planets.