1. The Life Cycle of Stars
Sample Student Paper (names removed)

2. The Birth of a Star
In order for a star to go through the process
of nuclear fusion, it needs fuel. These fuels
are mostly Hydrogen and Helium, also
accompanied by discrete amounts of
Carbon, Nitrogen, and Oxygen. While a Star
is using up one type of fuel, it must change
it's size and pressure in order to use another
fuel. Making these changes is a very gradual
process which usually happens over the
course of millions to billions of years. The
Star is born in an immense cloud of gas and
dust known as a Nebula.

3. Nebula
The word 'Nebula' in latin means 'cloud',
which is perfectly suited for what it is. A
Nebula is a cosmic cloud of dust and gas
floating in space. All the elements needed
for a Star are stored within the Nebula.
They are Hydrogen, Helium, and small
amounts of Oxygen, Carbon, and Nitrogen,
which are called 'heavier' elements The Crab Nebula
compared to Hydrogen and Helium. About
90% of the Nebula is Hydrogen, about 10% is
Helium, and about 0.1% are 'heavier'
elements as mentioned before. Nebulae are
among the largest objects in space. In fact,
many Nebulae are at least dozens, if not
hundreds of light years wide. There are also
five different types of Nebulae, Emission
Nebulae, Reflection Nebulae, Dark Nebulae,
Planetary Nebulae, and Supernova Nebulae.
By the way, Planetary Nebulae have nothing
to do with planets! The Eagle Nebula

4. Nebula to Star
In order for the new-born Star to go from
a Nebula to a Star, it must reach a critical
Mass of approximately 80 times Jupiter's,
due to accretion of matter. Once this
occurs, the internal pressure raises the
core temperature high enough to begin
nuclear fusion. Dust, gas, and other
materials gradually wait in the Nebula for
any gravitational disturbance to pass
through or by the Nebula. Once this
happens, it causes ripples and a process
called accretion. Accretion is growth in
size or extent. This means the Stars grow
larger.

5. Star
A Star is a bright globe of gas which
produces heat and light by nuclear
fusion. Stars consist mostly of
Hydrogen and Helium. Surface
temperatures of a Star vary from
2000o C to 30,000o C, depending upon
the content and size of the Star. The A Star named 'Electra'
hottest Stars tend to be a blue-white
color while red Stars are typically the
cooler Stars. The smallest Mass
possible for a Star is 155950.3608kg
because if it is any less, nuclear
fusion can not occur, therefore
causing the object to become a very
Our Sun
dim object, or very large planet.

6. Star to Red Giant
As a few billion years pass, a Star
runs out of it's protons. The result is
a core left with alphas. Even though
the outer layers still contain
Hydrogen, they aren't hot enough to
fuse. Without fuel, the Star begins
to cool and contract. The outer
layers sink into the core due to
Gravity, which causes them to heat
up. The Star now has a source of
energy. The core is now hotter than
it was during it's normal life. The
heat causes the Star to swell and
expand. By the time the radiation
reaches the surface of the Star, it
has become weak. Weak radiation
A Red Giant is a bright, immense Star
makes the Star red, as the Star
with a low mass nearing the end of it's
grows huge. I think it's obvious
evolution.
where they got the name from.

7. Red Giant
Red Giants are very bright, red
Stars (hence the name) that are
not very hot. Red Giants literally
blow up like a balloon because all
of the Helium that it possesses.
The size of a Red Giant can be 10
to 100 times the diameter of our
Sun. Red Giants of, formerly,
Betelgeuse (a Red Giant in the
large Stars are sometimes called constellation Orion)
Super Giants and can be up to
1000 times the diameter of our
Sun. They also have luminosities
of often 1,000,000 times greater
than that of our Sun.

8. Red Giant to White Dwarf
Once a small Red Giant runs out of fuel,
it begins to cool down and contract due
to gravity. The inner parts of the Star
contract which gives off heat and causes
the outer parts to expand. The
expansion of the outer parts causes
them to slowly separate and form a
Planetary Nebula. The inner parts of the
star continue to contract until it reaches
the size of Earth. Electrons begin to
overlap due to the atoms being crushed This picture depicts the Sun
together. Since two Electrons cannot as a white dwarf star and the
take up the same space, they begin to Sun now. The size
difference is quite obvious.
repel. This forms a small sphere of
matter, which is called a White-Dwarf
star.

9. White Dwarf
A White Dwarf is a very
small, hot Star and is the
last stage of the life cycle for a Star
such as our Sun. White Dwarfs
have a similar mass to our Sun,
except a White Dwarf is about 1% of
the Sun's diameter. Approximately, Comparison between Earth and a
a White Dwarf is the size of Earth. White Dwarf
White Dwarfs have a surface
temperature of 8,000o C or more,
but being small and hot costs the
White Dwarf a bright luminosity.
White Dwarfs have the luminosity
of 1% of our Sun's luminosity. A White Dwarf in Space

10. Red Giant to Supernova
Most small Red Giants die as a White
Dwarf, but the massive Red Giants die
in a more spectacular way, a
Supernova. After the fuel in a Red
Giant is exhausted, the core becomes
cooler and the internal pressure begins
to decrease, causing contraction. For
massive Red Giants, this is a disastrous
event which leads to the collapsing of
the Star. The outer layers start to gain
heat as they fall. This heat ignites
nuclear fusion in the outer layers This is Kepler's Supernova.
This Supernova occurred in
which causes them to explode. This is the Milky Way and is the
called a Supernova. For a few days, most recent Supernova to
this explosion is brighter than a whole be seen by the naked eye.
galaxy!

11. Supernova
A Supernova is an explosive death of a massive
Star. At its height, a Supernova can be as bright as
100 million bright Stars. Supernovae have been
accounted for creating heavier elements than
Hydrogen and Helium. Over the years, two types of
Supernovae have been found.
Kepler's Supernova.
Type I: A Supernova which happens in a binary star
system. It occurs by gas from one Star falling onto
a White Dwarf, causing it to explode.
Type II: A Supernova which occurs when a humongous
star, at least ten times more massive than our Sun,
explodes because of malfunctioning internal
nuclear reactions towards the end of it's life. These
large explosions either create a Neutron Star or a
Black Hole. A Supernova captured in
real time in August of
2006 through a gamma
telescope.

12. Supernova to Neutron Star
After the spectacular explosion of a
Supernova, the outer layers are blasted
off into space and form a Nebula. The
core is shrunk by gravity and condensed
into a sphere shape approximately the
size of Manhattan. The
Electromagnetic(EM) force keeps the
electrons out of the nucleus. Since the
EM force is the only thing that matters,
the Star wouldn't be able to shrink to
such a size simply because of the Mass
and number of atoms. However, because A Neutron Star is formed
of the Star's Mass, Gravity defeats the EM when a massive Star
force. Since the EM force is now broken, collapses, or in this case,
the protons and electrons combine to explodes.
make neutrons. All that is left are
neutrons, and the Neutron Star is formed.

13. Neutron Star
Neutrons Stars are stars that are mostly made up of Neutrons, hence the name,and are
produced by the massive explosion of a Supernova. Neutron Stars are very dense, therefore
they have a larger Mass compared to Stars such as our Sun. Typical Neutron Star have a Mass
A Neutron Star named
of three times our Sun's, but a diameter of only 20 km! If the Mass of a Neutron Star is greater 'RS 9862-81-8-9325421-
0 A.'
than 3 times that of our Sun's, then the gravity will be so strong that it will shrink into itself
and become a Black Hole.
The remains of a
Supernova with a Neutron
Star in the middle.

14. Supernova to Black Hole
As we just learned, a Neutron Star is made
from a Supernova explosion. Also, Neutron
Stars can create Black Holes. If the Neutron
Star becomes too big, the gravitational
forces become too much for the pressure
gradients and the collapse cannot be
stopped. The Neutron Star continues to
shrink until finally it becomes a Black Hole.

15. Black Holes
Little is known about Black
Holes, not even their Density. Of
the information that we do know
about them, Black Holes are the
remnants of the most massive
Stars in the universe. The Cygnus X-1, a Black Hole which is
located 6,070 light years away.
gravitational pull of a Black Hole
is so great that nothing can
escape from it, not even light,
therefore they are black.Black
Holes are believed to distort the
space around them, and also suck
in surrounding objects. The youngest Black Hole hole
known to man, SN1979C.

16. Work Cited
Stages of a Star- The Life Cycle of a Star [Internet]. cited 2012 Jan
3] . Available from: http://www.telescope.org/pparc/res8.html
Nebulae- Nebulae [Internet]. cited 2012 Jan 3] . Available from:
http://www.seasky.org/celestial-objects/nebulae.html
The Birth of a Star- Tangen KT, Weiss MW. Life Cycle of a Star
[Internet]. Mohegan Lake(NY):Oracle ThinkQuest; cited 2013 Jan
3] . Available from:
http://library.thinkquest.org/26220/stars/formation.html
Nebula to Star- Stellar Birth [Internet].[2006 Jan 7, cited 2013 Jan
3] . Available from:
http://burro.astr.cwru.edu/stu/advanced/stars_birth.html
Star to Red Giant- Seagrave WK. Red Giant [Internet]. :Penny Press
Ltd.; [2012, cited 2013 Jan 3] . Available from:
http://www.historyoftheuniverse.com/starold.html