Conley cis100 ppt_assignment

Star Basics
 The universe is full of stars.
 Somewhere between approximately 1022
and 1024 stars are currently believed to exist.
That’s more stars than grains of sand on the
Earth!
 Stars are probably the most important
objects in the universe.
 Every element larger than helium comes
from stars. We are technically stardust.

Star Formation
 Clumps of mostly hydrogen form
large molecular clouds inside
nebulas.
 As they accrete more matter, the
core becomes denser and
becomes a protostar.
 Eventually, the mass reaches a
critical point at which the internal
temperature is hot enough to
ignite nuclear fusion.
 The energy released from nuclear
fusion stabilizes the star against
it’s massive gravity.

Star Size
 The sun and
planets.
 The sun to VY
Canis Majoris
 VY Canis
Majoris is the
largest known
star.
 An estimated
9 billion suns
could fit inside
it!1

Star Death
 Stars will last as long as they have fuel to
burn.
 Most stars, like the Sun, are fueled from
the nuclear fusion of hydrogen into helium
in the star’s core.
 This occurs at around 10-15 million K in the sun,
and around 100 million K on earth.3
 When fusion stops, there is no longer
enough internal pressure to hold the star
up against it’s own gravity and the star
begins to collapse.

Star Death II
 In about 5 billion years, the Sun will
enter a red giant phase, initiating the
end of it’s life cycle.
 This occurs when all of the hydrogen
in the core is fused into helium.
 The lack of pressure in the core
allows the star to compress, which
begins heating the star further.
 This heat allows fusion in the outer
shell of the core to begin, and the star
swells tremendously.
 At it’s maximum size, the Sun’s perimeter
will just engulf the Earth, disintegrating it.

Supernovae
 Stars at least 8 times the mass of the Sun
undergo a more epic finale called a
supernova.
 There are many types of supernovae, but
in any case they are the most energetic
explosions in the known universe.
 During a supernova, a massive star can
eject more energy than the Sun will put out
in it’s entire lifetime.
 This is an equivalent of 200 trillion trillion
100 megaton H-bombs going off in a
matter of seconds.4

Core Collapse Supernovae
 Massive stars undergo core collapse,
resulting in a type-II supernova.
 Process:
 All of the stars hydrogen fuses into helium;
fusion ceases, diminishing internal pressure.
 Gravity overpowers the internal pressure
and crushes the core, heating it up further.
 Eventually, heat and pressure are strong
enough to fuse helium into carbon, and the
process repeats, fusing atoms into new
heavier elements.
 This continues up to iron. The atomic
structure of iron causes it to absorb energy
during fusion.
 Gravity overcomes the star, and a major
collapse occurs

Core Collapse Supernovae
II
 The inner core collapses in ¼ of a sec from
the size of the Sun to the size of Manhattan.
 The outer layers falling in nearly as fast,
collide with this new core and rebound with a
force comparable to nothing else in the
universe.
 The speed and intensity of the ejected outer
layers can outshine the entire surrounding
galaxy for several weeks.
 The blast is so powerful, it creates all of the
elements heavier than iron, spewing them
deep into space.

Neutron Stars
 The remnant cores of these supernovae collapse
into neutron stars.
 At this stage, the force of gravity is so strong, it
overcomes the repulsion of electrons.
 In the core of the star, electrons are combined with
protons to make neutrons and expel neutrinos.
 The star becomes stable from the internal pressure
of the neutron repulsion.
 The result is the remnants of a star so dense, a
teaspoon of it would weight around 10 billion tons on
earth!

Other Types of Neutron
Stars
 Pulsars-
 Neutron stars spin so fast
(100’s of times a second) that
electrons caught in the
intense magnetic field heat
up and emit radiation out of
the poles.
 All neutron stars do this, but
the radiation can only be
seen if the beam faces the
earth, making it appear to
pulsate.

Magnetars
 The most magnetic objects in the
universe.
 Magnetars are believed to form when
a neutron star is created with a very
fast spin.
 The phenomenon known as dynamo
action causes an intense magnetic
field around the star from the
convection of ionized gas.
 ‘Starquakes’ in the crust of the star
disrupt this field and the star emits
massive amounts of magnetic energy.
 If within a 1000 miles, a magnetar
would rip the iron from your blood!

Black Holes
 The ultimate in star death.
 Stars at least 20 times the mass of the
Sun end their lives as black holes.
 Currently, physicists can only speculate
what happens at the center of black
holes.

Black Holes II
 When the cores of the largest stars collapse, they
have such enormous gravity that the repulsion of
even neutrons can’t withstand it.
 At this point, the force of gravity is so strong that not
even light can escape it.
 Theoretically, with an infinite density, it can even
warp time itself.
 There is much about black holes that can’t be
explained with our current understanding of physics.
 The current laws of physics cannot explain what
happens at the center of black holes, though there
are many interesting theories.

Works Cited
1. Wittkowski, M.; Hauschildt; Arroyo-Torres, B.;
Marcaide, J.M. (5 April 2012). "Fundamental
properties and atmospheric structure of the
red supergiant VY CMa based on
VLTI/AMBER spectro-interferometry".
Astronomy & Astrophysics 540: L12.
2. Giacobbe, F. W. (2005). "How a Type II
Supernova Explodes". Electronic Journal of
Theoretical Physics 2 (6): 30–38
3. http://www.efda.org/fusion/how-fusion-works/
4. http://www.time.com/time/magazine/article/0,9
171,836188,00.html

Conley cis100 ppt_assignment

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