Download the life cycle of stars

THE LIFE CYCLE OF STARS
This star has
entered the
last stage
of its life cycle
• The first stage of star
formation is NUCLEAR
FUSION
• Gravity pulls clouds ofgas
and dust (nebulae) together
into a sphere – as it becomes
denser, it gets hotter and
the hydrogen changes to
helium.
• Stars are classified by:
1.
2.
3.
4.
5.
6.
7.
Size
Brightness
Mass
Color
Temperature
Spectrum
Age
TYPES OF STARS:
• MAIN SEQUENCE STARS – this is the
second phase and the longest phase
• Energy is generated in the core as
hydrogen atoms fuse into helium atoms
• Stars are about 98% Hydrogen and
Helium
• The sun in this stage (10 million yrs. to
become this stage – has been shining for
5 billion years ) Earth is 4.6 billion years
old
GIANTS AND SUPERGIANTS
• Third stage – RED GIANT
• RED GIANT – A large reddish star late
in its life cycle - a star that expands and
cools once it uses all of its hydrogen
• Eventually will shrink
• When shrinks – atmosphere grows large
and cools to a red giant or red
supergiant
• In 5 billion years the sun will become a
red giant
• Red giants – 10 or more times bigger
than the sun.
• Red Supergiants – at least 100 times
bigger than the sun.
WHITE DWARFS AND RED
DWARFS
• WHITE DWARF – a small, hot, dim
star that is the leftover center of
an old star
• No hydrogen left
• Can shine for billions of years
before they cool completely
• RED DWARF – low-mass stars
• Oldest stars in the universe
BLUE STARS
• BLUE STARS – very massive
blue stars are not in the main
sequence very long.
• They quickly use up the
hydrogen in their cores
• Expand and turn into giants or
supergiants
SUPERNOVAS
• A main sequence star with a mass
of more than about 10 Suns
experiences a spectacular end.
• It swells into a red supergiant with
cooling, expanding outer layers.
• Eventually its core collapses,
causing a huge explosion known as a
supernova
• A gigantic explosion in which a
massive star collapses and throws
its outer layers into space
NEUTRON STARS and
PULSARS
• NEUTRON STAR – a star that has
collapsed under gravity to the point
that the electrons and protons have
smashed together to form neutrons
• If the core of a supernova has
relatively low mass, the core will be
crushed into a tiny, super dense
neutron star
• PULSAR – a spinning neutron star
BLACK HOLE
• A volume of space in which
gravity is SO GREAT that
nothing can escape, not even
light, although objects can fall
in
• If the core of a supernova has a
mass of more than about two
Suns, its own gravity will squash
it further, into a black hole.
HR Diagram (page 592 – 593)
Shows the relationship between a star’s
surface temperature and absolute
magnitude
.
Hertzsprung-Russell
Diagram
• The temperature is given along the
bottom of the diagram.
Hertzsprung-Russell Diagram
• The absolute magnitude (brightness) is
given along the left side.
Hertzsprung-Russell Diagram
• The Hot (blue) stars are located on the
LEFT
• The Cool (red) stars are located on the
RIGHT.
Hertzsprung-Russell Diagram
• The BRIGHT stars are at the TOP.
• The DIM stars are at the BOTTOM.
• The DIAGONAL pattern where
most stars lie is the MAIN
SEQUENCE.
• The SUN is located in the
middle of the diagram.
• Average stars like the sun
become giants or supergiants
(Right) and then down to the
left to become white dwarfs.