life cycle of star

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THE LIFE CYCLE OF STAR
SOMETHING CHALLENGE
VIDHATE
G.B.

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Introduction
 OUR SCIENCE IS DISSCUSS ABOUT JUST
VISIBLE OBJECT ON EARTH.
 STAR HAS ALSO A LIFE.
 WHAT MEANT OF BLACK HOLE.

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Topics of Discussion
 LIFE CYCLE OF STARS.

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STARS
 There are more stars than any other object in the
universe.each is a spinning ball of hot,luminous
gas.more stars are made mainly of
hydrogen&helium.as these gases are convert to
heavier elements, energy is produced.a star has a
life cycle of billions of years that takes it through
many changes.the mass of star,however,dictates
how it will develop and die.

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* NUCLEOSYNTHESIS ** NUCLEOSYNTHESIS *
 Chemical elements are created insideChemical elements are created inside
stars by nuclear reactions.The processstars by nuclear reactions.The process
called nucleosynthesis,stars bycalled nucleosynthesis,stars by
converting hydrogen to helium.Aconverting hydrogen to helium.A
sequence of reactions at higher & highersequence of reactions at higher & higher
temperatures produces heavier &temperatures produces heavier &
heavier elements.The heaviest producesheavier elements.The heaviest produces
is iron.Most stars complete only part ofis iron.Most stars complete only part of
the process in their lifetime.the process in their lifetime.
 Four hydrogen nuclei (called protons)Four hydrogen nuclei (called protons)
are smashed together.Two positiveare smashed together.Two positive
particles escape,converting the twoparticles escape,converting the two
protons into neutrons.protons into neutrons.

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# STAR BIRTH #
 Stars are created from clouds of gas and
dust.the cloud spins,and the material
inside condenses and splits form smaller
clouds. These in turn in spin and
condense.each is proto star,a star in the
making.once material in the core of a
proto star has reached a creatical
density and temperature,nuclear
reactions start and energy is
produced.The STAR is born.
 Stars are shine due to the energy.
 IT MEANS STARS ARE CRAETED
FROM THE LARGE CLOUD.

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TYPES OF STARS
 There are two types stars.
 1) Orion Nebula :- an interstellar cloud
of gas & dust producing new stars.left of
center are four young & bright stars
known as the trapezium.
 2) Double stars :- About half the stars
are in a double star system.both were
created together from the same cloud of
material & force of each other`s gravity
keeps them together.

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! STAR CLUSTER !
 STAR CLUSTERS :- Group of stars living
together are called clusters.A group may contain
anything between a few or many thousand of
stars,all created from the same cloud of gas &
dust.the stars will be roughly the same age,but
each develops in its own way.
 Globular cluster(Hercules cluster):- older stars
are densely packed in globular cluster which are
spherical in shape.the Hercules globular cluster
contains several hundred thousand stars.
 Open cluster(Pleiades cluster) :- young stars
loosely bound in open clusters & will disperse
eventually.the stars in the Pleiades cluster are
still surroundedby cloud material left over from
their formation.

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! STAR DEATH !
 After billions of years,a star uses up its
gases in the nuclear reaction taking
place at its core.the star is starting to
die ,but death can still be billions of years
away.the mass of star dictates how it
dies.A star like sun gradually shed
material from its outer layers.one with
eight times the sun`s mass can end its
life in a gigantic explosion,called
supernova because the explosion looks
like a bright new star.

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# White Dwarf #
Stars with less than eeight solar masses
end their lives as white dwarfs.some of their
material has been cast off;the rest
condense to form a compact star about
twice the size of earth.
A match box of material from a white dwarf
would weight as much as an elephant.

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Neutron Stars & Pulsar
After the massive star explodes as a
supernova,gravity forces the core to collapse with
incredible force.The material is so densely packed
that it is compressed into Neutrons.The result is a
neutrons star,perhaps only 10-15 km (8-12 miles)
across
Pulsar are Neutron stars that spin
rapidly,sending out beam of radio
energy.
 A pin head of pulsar material would weight more
than the biggest supertanker.

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