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STARS
Init 2/20/2008 by Daniel R. Barnes
Note: As always, this presentation contains images taken without permission from the
world wide web. This presentation should not, therefore, be copied or distributed. In
fact, its very existence may be illegal.
Our Sun
Our sun is a typical star and is powered by nuclear reactions,
primarily the fusion of hydrogen to form helium.
Our Sun
The sun is about 109 times the diameter of the earth.
The sun has about 300,000 times the mass of the earth.
The sun coughs out tongues
of plasma that are much
larger than the earth itself.
Pictured at left is a coronal
mass ejection. The picture of
the sun is real, but the image
of the earth here is
superimposed. The earth
has never been that close to
the sun in real life.
Our sun is a typical star and is
powered by nuclear reactions,
primarily the fusion of hydrogen to
form helium.
Our Sun
Nuclear fusion is also used to boost
the power of fission explosions in
“hydrogen bombs”.
Our Sun
Nuclear fusion is also used to boost
the power of fission explosions in
“hydrogen bombs”.
Apparently, there are a lot of
misconceptions about the role
of hydrogen fusion in
“hydrogen” bombs.
Apparently, “hydrogen
bombs” derive most of their
power from uranium fission,
not hydrogen fusion.
According to Wikipedia,
scientists working on
“hydrogen” bombs never
called them “hydrogen
bombs”. Hydrogen fusion’s
role in a thermonuclear device
is to increase the yield of the
fissioning materials (uranium,
plutonium).
Our Sun
Our Sun
The sun gives out a continuous “solar wind” made of electrically
charged particles that may fly at speeds of millions of miles per
hour.
The solar
wind
changes
the shape
of the
earth’s
magnetic
field lines.
Red Giant
*As the name implies, red
giants are HUGE. They’re
not all the same size as
each other, but they are all
big.
*The little white dot is how
big our sun is right now,
compared to the red giant
Antares, the biggest one
shown in the picture at left.
Red Giant
*Our sun, and other stars
of of low to medium mass,
swell up to become red
giants when they run out of
hydrogen in their cores.
The process is somewhat
complicated.
Please take a deep breath.
Red Giant
Hydrogen in the
star’s core
finishes turning
into helium
Core
heats
up
Radiated heat
expands outer
layers of star
to giant size
Hydrogen
fusion in the
core stops
Core
cools
Core
shrinks
Helium in the
core begins
fusing to
become
carbon and
oxygen
Core pressure
increases
Gravity in the core
strengthens
Red Giant
*A red giant has
no hydrogen left
in its core, but the
helium there
fuses to form
carbon and
oxygen. The
hydrogen outside
the core fuses to
form helium,
which then sinks
down to join the
core and burn
with the rest of
the helium there.
White Dwarf
* Is the leftover remains of a red giant that ran out of nuclear fuel
* Has a mass comparable to the sun, but a size comparable to the
earth, and, therefore . . .
* Has a very very high density – Denisties vary, but a grape sizedpiece of white dwarf matter might have as much mass as a truck.
*No nuclear reactions – Therefore, what heat they have is left over
from the days when the star did carry out nuclear reactions
*Low luminosity, yet a very high temperature
*Small size means not much surface area, resulting in slow
cooling and low luminosity despite high temperature
*Eventually, they turn into black dwarves, but this process is so
slow that maybe the universe is too young for any to have gotten
to that stage yet.
White Dwarf
This graphic shows the relative sizes of IK Pegasi A (left), IK Pegasi B (lower center) and
the Sun.
White Dwarf
* Is the leftover remains of a red giant that ran out of nuclear fuel
* Has a mass comparable to the sun, but a size comparable to the
earth, and, therefore . . .
* Has a very very high density – Denisties vary, but a grape sizedpiece of white dwarf matter might have as much mass as a truck.
*No nuclear reactions – Therefore, what heat they have is left over
from the days when the star did carry out nuclear reactions
*Low luminosity, yet a very high temperature
*Small size means not much surface area, resulting in slow
cooling and low luminosity despite high temperature
*Eventually, they turn into black dwarves, but this process is so
slow that maybe the universe is too young for any to have gotten
to that stage yet.