Transcript main sequence star

Stellar Evolution
In the Beginning
• A star begins as a cloud of gas and dust
called a nebula
• According to Newton, the gravitational force
increases as the distance between molecules
decreases
• Particles come together to start to form a
sphere of gas and dust
• As the nebula shrinks it spins more rapidly
• The nebula’s shrinking and spinning causes it
to flatten into a disk shape.
Protostar
• Stage 1 of stellar evolution is the
formation of a protostar.
• The center of the rotating disk is called
a protostar
• The temperature increases from more
and more collisions of particles as they
get closer. The pressure also increases.
• When the temperature get to about
10,000,000º C nuclear fusion begins
and a star is born.
Main-Sequence Stars
• Stage 2 of stellar evolution is a main
sequence star.
• Stars remain main sequence stars for 90% of
their life. It is the longest stage in stellar
evolution.
• In the core, nuclear fusion is taking place.
The first fusion to take place is hydrogen
atoms fusing to become helium atoms.
• The star stays about the same size because
the gravity is pulling together even though
energy from nuclear fusion is pushing
outward.
• The star is stable as long as there is enough
energy to continue nuclear fusion.
Giants and Supergiants
• Stage 3 of stellar evolution are red giants and
supergiants.
• Begins when almost all of the gases are used up
by nuclear fusion and the star does not have
enough energy to continue nuclear fusion.
• The core of the star becomes unstable.
• The star expands and changes temperature and
luminosity (brightness).
White & Black Dwarfs
• This is the 4th and 5th stages of small mass stars.
• Small mass stars will collapse into white dwarfs
after being red giants.
• The outer gases are lost, which allows us to see
the core of the star. The white dwarf is very
dense and hot. The emit (release) less light than
they did when they were stars.
• As these white dwarfs cool they become fainter.
• When there is no more energy being emitted
(released), they are called black dwarfs.
Supernovas
• This is the 4th stage of large mass stars.
• Some red giants and red supergiants
explode in a supernova.
• Supernovas can result in one of three
things: neutron star, black hole, or nebula
Black Holes
• Some stars are so massive that they
cannot form neutron stars. Instead they
form black holes
• The force of gravity is so strong that
everything, including the core, is crushed
inward.
• The gravity is so great that light cannot
escape it.
Poster Requirements
• Title – Stellar Evolution or something
appropriate.
• All steps in stellar evolution included
• Three facts for each step (4 for Red Giant /
Nebula, because there are 2 different steps
with them, so 2 different facts under each
picture)
• A picture for each step
• Needs to show order (arrows to next step)
• Has to have color and labels for each step
• Be creative!!!