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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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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 EvolutionM 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

Protostar – contracting gas due to gravity. 1.4<M<~4 M>~4

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. Energy source – nuclear fusion.

Next stage – red giant. Size ~100 times Main Sequence. If not enough mass then Brown Dwarf. Energy source – nuclear fusion.

Stellar EvolutionFig. 12-2a, p.248 1.4<M<~4 M>~4

Fig. 12-4, p.250 1.4<M<~4 M>~4

HST Protostar with two jets 1.4<M<~4 M>~4

Fig. 12-5a, p.251

Protostar with two jets 1.4<M<~4 M>~4

Fig. 12-5c, p.251

Mass of He is 1.4<M<~4 M>~4

less than 4 H.

Difference gets

converted to

energy E = mc².

Fig. 12-6, p.252

Fig. 12-8, p.253 1.4<M<~4 M>~4

Proton - proton chain fusion in main Sequence stars. 1.4<M<~4 M>~4

Does not occur in one step. Also emit photon (γ) and neutrino (ν).

Fig. 12-10, p.255

- Main Sequence stars 1.4<M<~4 M>~4.
- 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.

Hydrostatic 1.4<M<~4 M>~4

equilibrium

in a main

sequence star.

Gravity is

balanced by

outflow energy

pressure

Brown dwarf 1.4<M<~4 M>~4

If protostar does

not have enough

mass to start

nuclear fusion

star contracts to

Brown dwarf

Brown dwarf

Fig. 12-11b, p.256

ν 1.4<M<~4 M>~4 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)
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