Transcript the life cycle of stars

THE LIFE CYCLE OF STARS
Chapter 15 – 2
Part 1
TYPES OF STARS
• A star can be classified as one type of
star early in its life, and as a different
type of star as it gets older.
• A star is classified differently as its
properties change.
The Life Cycle of
Sun-like Stars
• Like all natural cycles, the
stages in a star’s life
progress from birth to
death.
Nebula or Protostars
• A star begins life as a
ball of gas and dust.
• Gravity pulls the
materials into a sphere.
• As the sphere gets
denser, the temperature
rises to 10,000,000* C.
• Nuclear fusion occurs as
hydrogen combines into
helium.
Main-Sequence Stars
• After a sun-like star forms, it enters
the main-sequence.
• This is the second and longest stage of
its life.
• Energy is generated in the core and
causes the star to shine.
• The size of the star changes very little
as long as its supply of hydrogen nuclei
fuse into helium nuclei.
Nuclear Fusion
Giants and Supergiants
• When a main
sequence star uses
all its hydrogen in its
core, helium begins
to fuse.
• The center then
begins to shrink, and
the atmosphere
grows very large and
cools.
ANTARES
White Dwarfs
SIRIUS
• A white dwarf is a
small, hot, and dim
star that is the
leftover center of a
red giant.
• It slowly cools and
becomes smaller,
but can shine for a
billion years.
LET’S TRY IT!
• ACTIVITY: THE LIFE
CYCLE OF STARS