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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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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 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


Stellar evolution

Hubble image of gas and dust 1.4<M<~4 M>~4

around a cluster of young,

hot stars

Fig. 12-1, p.248


Stellar evolution1

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 Evolution


Stellar evolution

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


Stellar evolution

Main sequence stars 1.4<M<~4 M>~4

Protostar

Fig. 12-2b, p.248


Stellar evolution

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


Stellar evolution

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

Fig. 12-5a, p.251


Stellar evolution

Protostar with Jet 1.4<M<~4 M>~4

Jet

Fig. 12-5b, p.251


Stellar evolution

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

Fig. 12-5c, p.251


Stellar evolution

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


Stellar evolution

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


Stellar evolution

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


Stellar evolution

  • 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 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 (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.


Stellar evolution

Hydrostatic 1.4<M<~4 M>~4

equilibrium

in a main

sequence star.

Gravity is

balanced by

outflow energy

pressure


Stellar evolution

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


Solar neutrinos

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)


Stellar evolution

Homestake 1.4<M<~4 M>~4

Solar neutrino

Telescope

South Dakota

Fig. 12-12, p.256


Stellar evolution

Water detector for 1.4<M<~4 M>~4

neutrinos (ν) in

Japan.

Kamiokande

Fig. 12-13, p.257


Stellar evolution

Sudbury 1.4<M<~4 M>~4

Neutrino

Observatory

in Canada.

Fig. 12-14, p.258


Stellar evolution

Note: Planetary 1.4<M<~4 M>~4

nebula are NOT

related to

planets.

Fig. 12-15, p.258