Transcript The life cycle of a star

Science 9
THE LIFE CYCLE OF A STAR
GRAVITY
Gravity is a force that pulls objects toward each
other
 The more mass an object has, the more gravity it
exerts
 The Sun has stronger gravity than Earth
 The force gets smaller as the distance between
two objects increases

https://www.youtube.com/watch?v=hoLvOvGW3Tk
THE BEGINNING OF A STAR

All stars begin as nebulas
 Huge
clouds of gas and dust, composed mainly of
hydrogen and helium
 Matter forms into clumps due to gravity
 Clumps combine and pack closely together
 Nuclear fusion begins
 This is the beginning of a star’s “life”
NEBULAE
NEBULAE II
GIANTS AND DWARFS
When a star nears the end of its life, it runs out
of hydrogen and other fuels needed to produce
energy
 Pressure decreases in the star so the star
swells (gets bigger) and cools down (turns red)
 Stars equal to or smaller than the sun become
red giants
 Stars much larger than the Sun become red
supergiants

RED GIANTS I
RED GIANTS II
DWARFS

Smaller stars die when nuclear reactions
decrease, the core shrinks and parts of the star
float away

White dwarfs are small stars with a higher
temperature than red or yellow stars
DWARFS II
DWARFS I
SUPERNOVAS

An enormous explosion that occurs at the end
of a large star’s life

The core collapses inward to become either a
neutron star or a black hole

They are rare events
SUPERNOVAS
NEUTRON STARS
When extremely large stars die, the resulting
core is called a neutron star
 An extremely dense star made of neutrons

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A pulsar is a type of neutron star that emits
light and radio waves – the light appears as
pulses
NEUTRON STARS
BLACK HOLES
When a star at least 30x’s the size of the Sun
dies, the result is a black hole
 The core’s force is so strong, nothing can
escape, not even light
 They can exist undetected
 The x-rays of a black hole can be detected and
other objects orbiting it
 It is composed of matter only a few kilometres
across – should be called dark body

BLACK HOLES
MORE ABOUT BLACK HOLES
https://www.youtube.com/watch?v=3pAnRKD4r
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https://www.youtube.com/watch?v=cW7BvabYn
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