Sam and Brett
What Is A Star?
 Mass of gas together
held by gravity that is
self luminated.
Birth Of A Star
 Born from a Stellar Nebula
 Nebula made up of 97% H and 3% He
 Gravity causes gases and atoms to clump together
 Forms Protostar
Birth Of A Start Cont.
 Protostar very unstable
 In order to become a star must reach equilibrium
 Process called accretion
 http://www.youtube.com/watch?v=YU6X3SPZAJo
Types of Stars
 Protostar- The beginning stages of a star. Giant ball of
gas. Stage lasts around 10,000 Years
 Main Sequence Star- Majority of the stars in our galaxy
and universe. Vary in size and brightness. Fusion
from the hydrogen fuel produces an outward force that
counter-acts gravity’s inward force and creates
Hydrostatic Equilibrium. Examples are our Sun, Sirius,
and Alpha Centauri
Types of Stars Cont.
 Red Giant- Star has consumed its stock of hydrogen.
Fusion stops. No outward pressure to counteract the
inward pressure from gravity. Surface ignites
continuing the life of the star but also making it grow
up to 100x in size. Lasts only a few hundred million
years.
 White Dwarf- Star has run out of hydrogen fuel for its
core. The outward light pressure from the fusion
reaction stops and the star collapses inward under its
own gravity. It shines but has no fusion reaction.
Types of Stars Cont.
 Red Dwarf Stars- Most common kind of star. They
have a low mass so it is cooler than our sun. They are
able to keep the hydrogen fuel mixing in the core so
they last longer than most stars. Last for about 10
trillion years.
 Super Giant- The largest of the stars. Consume
hydrogen at fast rates. They live fast and die young.
They are very unstable.
When a Star Dies
 Once a star has consumed all its hydrogen in its core, it
dies.
 The smaller and Main Sequence stars turn into a
White Dwarf Star and eventually into a Black Dwarf.
When a Star Dies Cont.
 When a Super Giant dies, a Supernova occurs. From
there they can change into a Neutron Star or become a
Black Hole.
 Neutron Star- After a Supergiant has used up all its
hydrogen fuel, it dies in a Supernova. During the
Supernova the intense force of gravity crushes all the
protons and neutrons and creates a star completely
made up of neutrons.
When a Star Dies Cont.
 Black Hole- A black hole is formed when a star of
sufficient mass undergoes gravitational collapse, with
most or all of its mass compressed into a sufficiently
small area of space, causing infinite spacetime
curvature at that point. Such a massive spacetime
curvature allows nothing, not even light, to escape
from the "event horizon," or border. (taken from
about.physics.com)
 Black Holes have never been physically observed.
Video
 http://www.youtube.com/watch?v=0J8srN24pSQ
 http://www.youtube.com/watch?v=ou3TukauccM
Works Cited
 "Protostars." ASPIRE - Home. Web. 19 Jan. 2011.
<http://sunshine.chpc.utah.edu/labs/star_life/starlife_prot
o.html>.
 "Stars." JIM KALER. Web. 17 Jan. 2011.
<http://stars.astro.illinois.edu/sow/sowlist.html>.
 "Types of Stars." Universe Today. Web. 17 Jan. 2011.
<http://www.universetoday.com/24299/types-of-stars/>.
 "WMAP- Life and Death of Stars." Wilkinson Microwave
Anisotropy Probe (WMAP). Web. 18 Jan. 2011.
<http://map.gsfc.nasa.gov/universe/rel_stars.html>.