Download The Life Cycle of a star

The Life Cycle
of a star
By Ramunė Stabingytė and Kotryna
Bieliauskaitė
Kaunas “Vyturys” cathalic secondary school
What is a Star?
• A star is a huge sphere of
very hot glowing gas.
• When stars are grouped
together we call them
constellations.
• The big dipper is
constellation that we see
often.
http://en.wikipedia.org/wiki/File:Big_dipper_from_the_kalalau_lookout_
at_the_kokee_state_park_in_hawaii.jpg
The Sun
• The Sun is the only star in our solar system
– All eight planets, comets, and an asteroid belt,
revolve around the Sun.
• The Sun is a yellow, medium sized star.
http://en.wikipedia.org/wiki/File:Yohkohimage.gif
Classifying Stars
• Stars are classified according
to their temperature and
brightness.
• Hot Stars are Blue or White
• Cooler Stars are Red or Orange
Classifying Stars Cont…
• A young star is called a dwarf star
–They can be colored red, yellow, or
white.
• Our Sun is a yellow dwarf
• Older Stars are called Supergiants
–They can be colored red or blue.
The Timeline of a Star
• Our Sun is an average star. The chart below
shows the lifecycle of our sun over billions of
years.
http://en.wikipedia.org/wiki/File:Solar_Life_Cycle.svg
Birth of a star
• In space, there are huge
clouds of gas and dust
called nebulas.
• These clouds are made up
of hydrogen and helium
and are the birthplace of
new stars.
• Gravity pulls the hydrogen
gas in the nebula together
and it begins to spin,
• As the gas spins faster and
faster, it heats up and is
known as a protostar.
Protostar
• The second stage of star creation.
• At this point the temperature eventually reaches 15,000,000
°C.
• The cloud begins to glow brightly.
• At this stage, it contracts a little and becomes stable and is
called a main sequence star.
Main sequence star
• A star will remain in this stage, shining for
millions or billions of years to come.
• As the main sequence star glows, hydrogen in
the core is converted into helium by nuclear
reactions.
• Our sun is a main sequence
star.
Red giant phase
• When the hydrogen
supply in the core begin
to run out, the core
becomes unstable and
contracts.
• The outer shell of the star
starts to expand.
• As it expands, it cools and
glows red.
• The star has now reached
the red giant phase.
White dwarfs
• Gravity causes the last of the star’s matter to
collapse inward and compact, this is the white
dwarf stage.
• At this stage the star’s matter is extremely
dense.
• White dwarfs shine with a white hot light.
• The star has now reached the black dwarf
phase in which it will forever remain.
Massive stars
• Once massive stars reach the red giant phase,
the core temperature increases.
• Gravity continues to pull carbon atoms
together as the temperature increases
forming oxygen, nitrogen, and eventually iron.
• At this point, fusion stops and the iron atoms
start to absorb energy.
• This energy is eventually released in a
powerful explosion called a supernova.
Supernova
• A supernova can light
up the sky for weeks.
• The temperature in one
can reach
1,000,000,000 °C.
• The supernova then
either becomes a
neutron star or a black
hole.
Neutron star
• Neutron stars spin rapidly giving of radio waves.
• If the radio waves are emitted in pulses, the neutron
star is called a pulsar.
Black hole
• The core of a massive star
that has 8 or more times
the mass of our Sun
remains massive after the
supernova.
• It has now become a black
hole which readily attracts
any matter and energy that
comes near it.
• Black holes are not visible,
they are detected by the Xrays which are given off as
matter falls into the hole.
How do the sizes of the stars compare?