stellar evalution

1. STELLAR EVOLUTION
BY
SHANKAR

3. NEBULAE
• Stars form from nebulae which a large clouds
of gas mainly hydrogen and some dust and
heavier elements.
• These clouds are very huge.
• The only force acting on the particles of the
nebulae is gravity.

5. GRAVITY ON NEBULAE
• Gravity slowly pulls the gas.
• When this happens the nebulae contracts.
• Contraction leads to a higher pressure , thus a
higher temperature. Higher temperature
makes these clumps of dust glow.
• It contract even more , leading into an even
higher temperature. The clump makes a
spherical shape and glows even more. This is
called PROTOSTAR.

6. NUCLEAR FUSION
• Particles in the core are packed close together
and moving faster now hydrogen nuclei is
make helium nuclei.
• Nuclear fusion has begun release the huge
amount of energy.
• In this stage A STAR IS BORN.

7. SIZE OF A STAR
• The size of the star determined by very
delicate balance.
• Gravity always wants to make the star small.
Gravity wants to collapse the star.
• But the nuclear fusion produces the heat,
produces the pressure through the out side.

8. ..
• The size of the star determined by this
balance.
• If the thermonuclear fusion would increase in
strength the star becomes bigger.
• If it decrease in strength the star will shrink.

9. RED GIANT
 IN CASE OF A AVERAGE STAR LIKE OUR SUN.
 When the gravitational force are weakening ,
thermal force is slowly wining cause the star
to expand .
 As a star expand it is cooling , these larger
cooler stars are called RED GIANT.

10. ENDING STAGE
• Thermal forces are weakening , sooner the
gravity again wins.
• The core of the red giant collapses into a small
white dwarf.
• Where the star ends up at the end of its life
depends on the mass it was born with.
• When a star born with the 8 times mass of our
sun it will become a white dwarf.

11. Chandrasekhar limit
• Chandrasekhar calculated the maximum mass
of a white dwarf,
• It can only be 1.4 times mass of our sun.
• If the mass become longer the white dwarfs
become unstable and collapse.

12. Ending of massive stars
• When a star born with 8 to 25 solar mass it
will become a NEUTRON STAR.
• Neutron stars are purely made up of neutrons,
the neutron stars would be formed in
supernova explosion.
• When a star born with more than 25 solar
mass it will become a BLACKHOLE.

13. /
THANK YOU!!!