FORM 2 CHAPTER 11 STAR AND GALAXIES notes

CHAPTER 11

STARS AND GALAXIES
IN THE UNIVERSE

There are millions of galaxies in
the universe.

A galaxy is a set of bodies consisting of
millions of stars with gas, clouds and
dust particles.

All components are held together by
gravitational force.

11.1 STARS AND GALAXIES IN THE
UNIVERSE

 3 types of galaxies (based on shape):
a) Elliptical galaxies
b) Spiral galaxies
c) Irregular galaxies



OUR GALAXY : The Milky Way

 The MilkyWay is a medium large spiral galaxy.
 Our solar system is located at the edge of one of the

spiral arms of the MilkyWay.
 The MilkyWay consists of approximately 200 billion

stars and the Sun is one of it.



STARS are celestial objects that made

mostly of hydrogen and helium that

STARS can produce light and heat
from the nuclear reaction inside their
cores

The birth of a star

1. A star is born from nebula.

2. Nebula is a large cloud made up of dust and gases such as
helium and hydrogen.

3. Gravity pulled the dust and gases in a nebulae together.

4. The core shrinks and become dense.Temperature and
pressure increased.

5. When the core became hot and dense enough, nuclear
reaction started.

6. Huge amount of heat and light energy is released. A star is
formed (protostar)

7. The new star continue to expand and becomes star of
certain size.

The Death of Stars

 1. A star will die once the hydrogen gas in its core is used up for
its nuclear reaction.

2.Then the core would begin to contract and its outer parts expand
to become red giant stars.

3.If the star is average star, the red giant star would change into
white dwarf star.

4. If the star is large star, a red giant star would expand to become a
super giant star then explode and form a neutron star.

>> This explosion known as supernova, produces a lot of heat and
light energy

5. If the star is super-large star, a red giant star would expand to
become a super giant star then explode and form a black hole.

>> Black hole is a region which has strong gravitational
attraction and suck all matters into it including light.

The life cycle of a star

The Various Types of Stars

Some Of The Ways That Stars Differ From Each
Other



FOUR MAIN GROUPS OF STARS

Name Characteristics

White dwarf Dim, compact stars

Neuron stars Very dense, small stars

giants Large stars.Their diameters are
Supergiants 10 to 100 times that of the Sun

Even larger than giants.



The universe

 The universe consists of billions of galaxies, stars, planets,
particles and all the objects in outer space.

END OF
CHAPTER

Created by Fariha Subri