Stars are huge spheres of hot glowing gas that produce light and energy through nuclear fusion. They are born in cold clouds of gas and dust called nebulas, which collapse under gravity and heat up. There are many types of stars including red dwarfs, yellow stars like our Sun, giant stars, and massive blue giants. Nearly all stars belong to galaxies which range in shape and can contain billions of stars. Most stars end their lives by expanding into red giants and shedding their outer layers, leaving behind dense white dwarfs or black holes if they are especially massive.

1. LIFE OF STARS

2. Index
• What is a star?
• Stars birth
• Types of stars
• Galaxies
• Stars death

3. WHAT IS A STAR?
• A star is a huge sphere of very
hot, glowing gas. Stars
produce their own light and
energy by a process called
nuclear fusion.
• Stars come in a variety of
sizes and colors. Stars which
are smaller than our Sun are
reddish and larger stars are
blue.

4. STARS BIRTH
• Stars birth places are huge, cold clouds of gas and
dust, known as 'nebulas'.
• As the cloud gets smaller, it breaks into clumps.
Each clump eventually becomes so hot and dense
that nuclear reactions begin. When the temperature
reaches 10 million degrees Celsius, the clump
becomes a new star.

5. TYPES OF STARS
• There are several different kinds of stars in the sky.
Some are very big. A couple of stars have been
found that are 100 to 200 times larger than the sun.
Some very old stars are smaller than the Earth.
Scientists study stars and place them in groups
based on how they are alike and how they are
differentV

6. Red dwarf
• Red Dwarf stars are smaller than
our sun and have less mass.
These stars burn their fuel very
slowly, which allows them to live
a very long time. This also
causes these stars to not shine
as brightly as others
• They are red because they only
burn a little bit of fuel at a time,
they are not very hot compared
to other stars.

7. Yellow stars
• Like the Sun, these medium-sized
stars are yellow because they have
a medium temperature. Their higher
temperature causes them to burn
their fuel faster.
• Near the end of their lives these
medium-sized stars swell up,
becoming very large. When this
happens to the Sun, it will grow
large enough to engulf even the
Earth.
• When is this going to happen? Don't
worry, the sun is only about 5 billion
years old. It still has another 5 billion
years more.

8. Blue giant stars
• Blue stars are large and compact,
this causes them to burn their fuel
quickly. These stars often run out of
fuel in only 10,000 - 100,000 years.
• A blue giant is extremely bright.
There are the most common we see
at night.
• Blue giant stars die in a spectacular
way. They grow larger just like the
sun-sized stars, but then instead of
shrinking and forming a planetary
nebula, they explode in what is
called a supernova. Supernova
explosions can be brighter than an
entire galaxy.

9. Giant stars
• Remember when we talked
about sun-sized stars? We
said that at the end of their
lives these stars expand,
taking up much more space
than before. This is exactly
what a Giant Star is.
• As a sun-sized star gets old, it
starts to run out of its hydrogen
fuel. When the process of
burning hydrogen in the star's
core begins to slow down, the
core gets more compact and
dense.

10. Super giant stars
• A super giant star is the exact
same thing as a giant star only
much bigger.
• The only difference between
Giant Stars and Super Giant
Stars is their size. Super Giant
Stars are much bigger. If the
Sun were replaced by a super
giant star, it would extend from
the center of our Solar System
almost all the way out to
Uranus.

11. http://youtu.be/nCUS2uNGw7k
http://youtu.be/nCUS2uNGw7k
http://youtu.be/gT8WrjBEaHM
http://youtu.be/gT8WrjBEaHM

12. GALAXIES
• Nearly all stars belong to gigantic groups known
as galaxies. The Sun is one of at least 100 billion
stars in our galaxy, the Milky Way. And there are
billions of galaxies in the Universe.
• Everywhere we look in the sky there are galaxies of
different shapes and sizes. Some are spirals, with
curved arms wrapped around a bright central
core.
• They contain up to 10 million million stars, but they
have very little gas or dust. Nearly all galaxies
have a supermassive black hole at the centre.
• Galaxies were born only a few hundred million
years after the Universe was created. At that time,
about 13 billion years ago, the galaxies were small
and much closer together. Collisions were
common.
• Since then, the Universe has been expanding.
Most galaxies are moving apart at high speed.

13. STARS DEATH
• Most stars take millions of years to die.
When a star has burned all of its hydrogen
fuel, it expands to become a red giant.
• After puffing off its outer layers, the star
collapses to form a very dense white dwarf.
Over billions of years, the white dwarf cools
and becomes invisible.
• Big stars die early and try to keep alive by
burning different fuels, but this only works
for a few million years. Then they blow
themselves apart in a huge supernova
explosion.
• For a week or so, the supernova outshines
all of the other stars in its galaxy. Then it
quickly fades and turns into a black hole –
surrounded by an expanding cloud of very
hot gas.