Brief description about birth, maturity ageing and death stages of star

1. STELLAR EVOLUTION
Mrs.P.Kanmani,M.Sc.M.Phil.,
Mrs.P.Kanmani M.Sc., M.Phil.,
Assistant Professor,
Department of Physics (SF),
V.V.Vanniaperumal College for Women,
Virudhunagar.

2. STELLAR EVOLUTION
Mrs.P.Kanmani,M.Sc.M.Phil.,
Outline
Evolution
Stages of a
Star
Birth of a star
Maturity
Ageing Stars
Death of a Star

3. STELLAR EVOLUTION
Mrs.P.Kanmani,M.Sc.M.Phil.,
Birth of a star
Stars are born in
cold clouds of
interstellar gas and
dust floating in
space called Nebula.
Mutual
Gravitation
Form centres of
condensations
called Protostars.
Centre of
Gravity
Pressure and
temperature
increases to a
point where
hydrogen burning
is possible.

4. STELLAR EVOLUTION
Mrs.P.Kanmani,M.Sc.M.Phil.,
 The outpouring energy of a protostar creates enough pressure to stop
gravitational contraction.
 A thermal equilibrium is established and temperature is sufficient to
shine and be visible.
 At this stage the star is completely convective.
Birth of a star

5. STELLAR EVOLUTION
Mrs.P.Kanmani,M.Sc.M.Phil.,
Maturity
 When the transfer of energy in the core of a protostar changes from
convection to radiation it becomes main sequence star.
 Now the core temperature is high enough to start a nuclear reaction.
 A massive or super massive star will form in a few thousand years
where as less massive star take a few million years.

6. STELLAR EVOLUTION
Mrs.P.Kanmani,M.Sc.M.Phil.,
Maturity
 In the process of hydrogen burning helium is formed.
 To maintain thermal equilibrium the liberated energy in the interior is
radiated from the surface.
 Due to radiation the temperature rises and star becomes more and
more luminous.

7. STELLAR EVOLUTION
Mrs.P.Kanmani,M.Sc.M.Phil.,
Ageing Stars
 The helium formed by fusion is collected at the centre where no
hydrogen is available for burning.
 To maintain thermal equilibrium the core starts to contract and outer
layer expands outwards.
 As the size increases the energy radiated per unit area of surface
decreases and temperature falls down to 3000 K to 4000 K.

8. STELLAR EVOLUTION
Mrs.P.Kanmani,M.Sc.M.Phil.,
Ageing Stars
 The temperature drop changes the colour to red and is approximately
called red giant.

9. STELLAR EVOLUTION
Mrs.P.Kanmani,M.Sc.M.Phil.,
Death of a Star
 When the temperature of Helium core reaches 108 K helium nuclei start
fusing into carbon through triple alpha process.
 The death of a star is determined by its mass.

10. STELLAR EVOLUTION
Mrs.P.Kanmani,M.Sc.M.Phil.,
Death of a Star
Less massive
stars
Red giants
White dwarfs
Massive or super
massive stars
Super nova
explosion
Neutron stars
or black holes

11. STELLAR EVOLUTION
Mrs.P.Kanmani,M.Sc.M.Phil.,
Summary

12. STELLAR EVOLUTION
Mrs.P.Kanmani,M.Sc.M.Phil.,
Happy Learning
Thank You…