Transcript The Life of a Star

The Life of a Star
Cathcart
science
“Which motion of earth
causes which apparent
motion of stars?”
• Rotation= the earth is spinning
• Revolution=the earth orbits the
sun
• Stars appear to circle Polaris
during the night.
• Different constellations are
visible different months of the
year.
A star begins….
• …as a ball of gas and dust.
• Gravity pulls the gas and dust
together into a sphere.
• The sphere becomes dense and
hot.
• Nuclear fusion changes
hydrogen to helium.
Main-sequence stars….
• ….are in the second and
longest stage.
• As long as they have
hydrogen atoms to fuse into
helium atoms they just keep
on releasing lots of energy.
Red giants….
• ….are what stars can become
after the main-sequence stage.
• This is a star that expands and
cools because it has used up all
of its hydrogen.
• The center of the star shrinks,
but the atmosphere gets very
large.
• The star may become a
supergiant (100 times bigger
than the sun).
White dwarfs….
• …..are stars in their final
stages.
• This is a small hot star that is
the leftover center of a star.
• A white dwarf can no longer
generate energy, but it can
keep shining for billions of
years
Really massive stars….
• …might not make it to the white
dwarf stage.
• Massive stars might explode in
a bright flash called a
supernova.
• A supernova can be brighter
than a whole galaxy.
A neutron star…
• …forms from the center of a
massive star that has
exploded into a supernova.
• A neutron star has collapsed
under gravity to the point
that all of its particles have
become neutrons.
A pulsar….
• ….is a neutron star that
is spinning.
If…..
• …..the center of the collapsed
star is massive enough
• ….and it collapses further
because of the strength of its
own gravity
• ….it could become a black
hole.
A black hole…..
• ….is a place in space where the
gravity is so strong nothing can
escape
• not even light.
You have a choice…
• You may write a story about the
life of a star.
• Or
• You may create a comic strip
about the life of a star.
• Either way, you will be graded
as follows:
Your star must…
• Begin as a ball of gas and dust.
• Go from there to mainsequence, red-giant or
supergiant, then to white dwarf.
• Or be a massive star that goes
from main-sequence to
supernova to neutron star
(perhaps pulsar) and perhaps
becomes a black hole.
For a perfect grade..
• The stages need to be named.
• The stages need to be in
order.
• The story or comic strip needs
to show an understanding of
each stage.
• EXTRA POINTS FOR
ENTERTAINING THE
TEACHER!