LIFE CYCLE OF A STAR

LIFE CYCLE
OF A STAR
© 2004 Plano ISD, Plano, TX
All of It the is an little area bright of dust spots and are gas stars in
forming space out where of the stars gas. are This “born”. is a nebula.

Life Cycle Of A Star
Stars change and evolve in a
predictable pattern over time.
The path a star takes over its
lifetime depends on the star’s
MASS. I.
© 2004 Plano ISD, Plano, TX

The Nursery
All stars begin their life in a
NEBULA.
A nebula is a gigantic cloud of
dust, gas, and plasma in
space.
II.A.
If there is enough matter in
the nebula, gravity will start
to pull everything together
into a PROTOSTAR.
A protostar is an infant
star…the equivalent of a
newborn baby.
© 2004 Plano ISD, Plano, TX
III.A.
The Horsehead Nebula

Average Stars
Average stars spend most of
their lives as boring, normal
MAIN SEQUENCE stars.
Our sun is a great example.
It is about 4.5 billion years
old.
Average stars can live up to
10 billion years before they
begin to die out.
IV.A.1.
They create heat and energy
through the process of nuclear
fusion.
IV.A.2.
© 2004 Plano ISD, Plano, TX

Average Stars
As an average, main sequence
star gets older and larger, it
becomes a RED GIANT.
This means the end is getting
near.
Red giants are incredibly
massive and bright, but are
relatively cool compared to
younger stars…the fire is going
out.
IV.B.1.
When our sun becomes a red
giant, Earth will look like
Mercury.
© 2004 Plano ISD, Plano, TX

Average Stars
Eventually, the fuel for the
nuclear reactions at the heart
of the star runs out.
Average red giants simply
collapse in a “puff” of gas.
What’s left behind is a small
core of carbon and oxygen
called a WHITE DWARF.
IV.C.1.
A small amount of heat is still
produced, like an oven that’s
still warm after its been
turned off.
Sirius A and B
© 2004 Plano ISD, Plano, TX

Massive Stars
Massive stars are much larger
and brighter than their
smaller relatives.
Massive stars will spend much
of their lives blueish-white
because they are so hot.
Eventually, they will make it
to the RED SUPERGIANT
stage as they age and cool.
This is just like a red giant
except bigger and hotter. A
LOT bigger and hotter. V.A.1.
The constellation Orion has
two red supergiants in it.
© 2004 Plano ISD, Plano, TX

Massive Stars
Red supergiants don’t “puff”
away when they get older like
their smaller relatives…they
explode.
This SUPERNOVA ejects gas,
radiation and a blast wave far
into space.
V.B.1.
It will light up the skies for
weeks or months.
A supernova will briefly
outshine its own galaxy when it
explodes.
© 2004 Plano ISD, Plano, TX

Massive Stars
NEUTRON STARS are one of
the possible leftovers after a
supernova.
In a neutron star, all the
leftover matter from the
massive star is crushed and
condensed down to a core
smaller than the Earth. V.C.1.
They are extremely dense and
have tremendous amounts of
gravity.
Neutron stars are also known as
PULSARS because of the pulses of
gamma rays they give off.
© 2004 Plano ISD, Plano, TX

Massive Stars
The last option for a massive
star is the most frightening.
The largest of the massive
stars have so much mass that
after a supernova, the
leftover material collapses in
on itself to form a BLACK
HOLE.
There is so much gravity
created by the density of the
leftover material that a hole
in space is ripped open. V.D.1.
Not even visible light can
escape.
© 2004 Plano ISD, Plano, TX

Life Cycle Of A Star
© 2004 Plano ISD, Plano, TX

© 2004 Plano ISD, Plano, TX