Transcript Life-Cycle of a Star - Warren County Schools

The Life-Cycle of a Star
The Nebular Model
• A nebula is just a cloud of interstellar dust and
gas.
• Nebulae are sometimes referred to as “baby
factories for stars”.
• Stars are formed from the dust and gas from a
nebula.
• The nebula is important because it is dense enough
to form stars – most other locations in the universe
are not that dense.
• are believed to be formed by exploding stars or
left over from the beginning of the universe.
The Bubble Nebula
The Ghosthead Nebula
Do you see the ghost?
The Eagle Nebula
The Beginning
• Our Solar System
began as a Nebula.
The Beginning
• Our Solar System
began as a Nebula.
• Something, a large star
passing by maybe,
started the nebula
spinning in a
counterclockwise
direction.
The Beginning
• As this loose mass of
gas and dust spun, it
began to flatten out,
kind of like pizza
dough.
The Beginning
• As this loose mass of
gas and dust spun, it
began to flatten out,
kind of like pizza
dough.
The Beginning
• As this loose mass of
gas and dust spun, it
began to flatten out,
kind of like pizza
dough.
• But as it flattens it
begins to form a bulge
in the center.(I wonder
what will form here?)
The Beginning
• The Sun will form in
the bulge and the
planets will form in
the accretion disk.
• 99% of all the mass of
the Nebula ends up in
the bulge.
Sun
Accretion Disk
The Formation of the Sun
• Our Sun forms in the
bulge of the nebula.
• As the gasses and dust
became more compact,
they began to attract
each other towards the
center. This is called
gravitational contraction.
The Formation of the Sun
• As the particles got closer
together they sped up - this
increased their kinetic energy
(energy of motion).
• Since this increase in kinetic
energy also means a increase in
temperature, the bulge is getting
hotter.
• It is also getting denser.
• At this point what will become
our local star, the Sun, is just a
protostar.
The Formation of the Sun
• Ultimately the temperature
and density reach critical
values for nuclear fusion to
occur.
• At this point our protostar
has become a star. We are
so proud!!!
The Formation of the Sun
• In nuclear fusion, two hydrogen
atoms are given enough energy
to come together and form a
helium atom.
• This releases more energy.
• The energy released in this
process is what powers the sun.
Some of it causes more
hydrogen to fuse into helium,
and the rest works its way into
space.
• Let’s watch.
Fusion of Hydrogen in the Sun
H
H
Fusion of Hydrogen in the Sun
H
H
Fusion of Hydrogen in the Sun
H
H
Fusion of Hydrogen in the Sun
H
H
Fusion of Hydrogen in the Sun
H
H
Fusion of Hydrogen in the Sun
H
H
Fusion of Hydrogen in the Sun
H
H
Fusion of Hydrogen in the Sun
H H
Fusion of Hydrogen in the Sun
H
H
Fusion of Hydrogen in the Sun
He
The fusion reaction in the core of a star doesn’t stop at Helium.
Helium (Atomic # = 2) can fuse with Hydrogen (Atomic # = 1)
to form Lithium (Atomic # = 3).
Two Helium (Atomic # = 2) atoms can fuse to form Beryllium
(Atomic # = 4).
In stars the size of the Sun (medium to small) this process
continues up to Carbon (Atomic # = 6). Larger stars can
provide more energy so this process continues up to Iron
(Atomic # = 26).
This is another view of the Eagle Nebula. At
the top of each pillar you can see stars being
born.
This is a view of another Nebula, Abaurigae.
At the center you can see a star being born.
This is a view of another Nebula. In the upper
right you can see a star being born.
This is a view of the Orion Nebula. The bright spot
is a star which has formed. The dark ring is an
accretion disk where planets may form.
Fusion & Gravity
Fusion exerts an external Pressure outward on the star
and gravity pulls inward. The two opposing forces
balance each other out. This determines the size of the
star
Fusion & Gravity
Fusion exerts an external Pressure outward on the star
and gravity pulls inward. The two opposing forces
balance each other out. This determines the size of the
star
Fusion & Gravity
Fusion exerts an external Pressure outward on the star
and gravity pulls inward. The two opposing forces
balance each other out. This determines the size of the
star
Fusion & Gravity
Fusion exerts an external Pressure outward on the star
and gravity pulls inward. The two opposing forces
balance each other out. This determines the size of the
star
Fusion & Gravity
Fusion exerts an external Pressure outward on the star
and gravity pulls inward. The two opposing forces
balance each other out. This determines the size of the
star
Fusion & Gravity
Fusion exerts an external Pressure outward on the star
and gravity pulls inward. The two opposing forces
balance each other out. This determines the size of the
star
Fusion & Gravity
Fusion exerts an external Pressure outward on the star
and gravity pulls inward. The two opposing forces
balance each other out. This determines the size of the
star
Gravity & Fusion
• Gravity & Fusion determine
the size of a star.
• Gravity pulls the star
inward.
• Fusion pushes the star
outward.
• The size of the star is
determined by the
equilibrium between these
two forces.
Size and Color of a Star
The size of a star is determined by
the tug-o-war between gravitational
contraction and the outward
pressure of the fusion reaction.
Size and Color of a Star
The size of a star is determined by
the tug-o-war between gravitational
contraction and the outward
pressure of the fusion reaction.
But the speed of the fusion reaction
determines the color of the star.
Size and Color of a Star
The size of a star is determined by
the tug-o-war between gravitational
contraction and the outward
pressure of the fusion reaction.
But the speed of the fusion reaction
determines the color of the star.
If the fusion reaction is slow, the
star is small, cool (3200 K) and red.
Size and Color of a Star
The size of a star is determined by
the tug-o-war between gravitational
contraction and the outward
pressure of the fusion reaction.
But the speed of the fusion reaction
determines the color of the star.
If the fusion reaction is a little
faster, the star is bigger, warmer
(5800 K) and yellow-orange.
Size and Color of a Star
The size of a star is determined by
the tug-o-war between gravitational
contraction and the outward
pressure of the fusion reaction.
But the speed of the fusion reaction
determines the color of the star.
If the fusion reaction is even faster,
the star is bigger, hot (45,000 K)
and blue.
Size and Color of a Star
Ironically, the bigger the star, the
shorter its lifespan.
This is because the fusion reaction
is running so fast in large stars that
the available fuel is used up very
quickly.
A blue star lasts around 800,000
years.
Our Sun (Yellow) 10 billion years.
A red star about 2,000 billion years.
The Death of Our Sun
In about 5 billion years our sun will use up all its Hydrogen and the
fusion reaction will stop. At this point gravity is the only force in the
sun and the sun will begin to collapse.
The Death of Our Sun
But as the sun begins to Collapse it will get hotter, just like when it
first formed.
The Death of Our Sun
And Hotter !!!
The Death of Our Sun
Until fusion begins again and …..…..
The Death of Our Sun
The sun expands …..
The Death of Our Sun
Into a …..
The Death of Our Sun
Until …..
a red giant
enveloping and ultimately
incinerating the inner 3
planets. This will include
us.
Ouch !!!!
Betelgeuse
Betelgeuse is a red supergiant
located in the constellation of
Orion. Betelgeuse is Orion’s right
shoulder.
Betelgeuse will go supernova
within the next 10,000 years.
When it does we will see it for
two weeks during the day and it
will cast shadows at night.
If you are lucky you may get to
see this spectacular event!!!
The Death of Our Sun
Finally the Sun will use up its remaining
fuel creating elements up through
Carbon. Bigger, hotter stars can actually
create elements through Iron.
The Fusion Reaction
Stops at Carbon (Iron)
The Death of Our Sun
At this point the outer layer of the sun will be
blown into space along with the elements formed in
its core and the heavier elements formed during the
“explosion”. These elements will be used to form
other stars and planets.
The atoms that formed you probably came from the
death of an earlier star!!!!!
What remains of the Sun will collapse into a white
dwarf- a cooler but denser burnt out ember of the
sun
White Dwarf H1504
Eventually this
white dwarf will
cool and no
longer emit light.
At this point it
will no longer be
visible.
This is the fate of
our Sun.
If the sun were slightly larger it would
become a neutron star.
A neutron star is much denser than a white
dwarf.
1 teaspoon of matter from a neutron star
would weigh as much as a mountain.
If the sun were 3 times as large it would
never stop collapsing on itself and become a
black hole.