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THE LIFE CYCLE OF A STARScience 9
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
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=3pAnRKD4raY
https://www.youtube.com/watch?v=cW7BvabYnn8
