Our solar system is made up of the
b. 9 planets
d. Asteroids, meteoroids, and comets
The sun is the center of the solar system
and other planets go around it in the
The sun is the solar system’s star and it
provides heat and light.
Planets are big objects that go around the
Unlike stars, planets do not produce heat
and light. They appear shining in the sky
because they reflect the light of the sun.
There are nine planets in our solar
Mercury, Venus, Earth, Mars, Jupiter, Satur
n, Uranus, Neptune and Pluto (arranged
according to the distance from the Sun.)
Each planet has its own features.
• The nearest planet to the sun.
• A very hot planet as it is very close to the sun.
• The second smallest planet after Pluto.
• The nearest planet to earth.
• The hottest planet
• Covered by thick poisonous yellow clouds.
• The only planet with living organisms
• There are air, warmth and water for plants
and animals to survive.
• Known as the red planet because it is covered
with fine reddish soil.
•The largest planet
•Spins very fast, takes less than 10 hours
for one spin.
•Most beautiful planet. It is surrounded by
a spectacular set of rings.
•Each ring is made up of billions of pieces
of ice rock
•A blue planet with a thin ring
•Has a rocky core covered with layers of
•Also a blue planet similar to Uranus.
•Has a small rocky core covered with
thick gases that reflect a bluish light.
• the smallest planet in the solar
• The farthest planet from the sun.
• A very cold planet
Each planets has its own moons except for
Mercury and Venus.
All the planets together with their moons go
around the Sun in their own path called orbits
which are ellipses.
The powerful gravity of the sun keeps the planets
The further the planet from the sun, the bigger its
orbits is. Pluto has the biggest orbit and Mercury
has smallest orbit.
Therefore, the planets have different length of
years. One planet’s year is the time needed by the
planet to make a complete orbit.
As each planet orbits the Sun, it also spins like a top.
The planet’s day is the time it takes to spin around
Planet Number of
Mercury - 58 88 Earth
Venus - 108 225 Earth
Earth 1 150 365 ¼
Mars 2 230 687 Earth
Jupiter 16 780 119 Earth
Saturn 20 1470 29.5 Earth
Uranus 15 2870 84 Earth
Neptune 8 4500 165 Earth
Pluto 1 6000 248 Earth
Every planet spin on its axis from west to
east except for Venus and Uranus.
Venus spins from east to west.
The axis in which Uranus spins is titled
right over. Therefore, Uranus spins from
top to bottom like a wheel.
From its discovery in 1930 until 2006,
Pluto was demoted in our Solar System. In
August 2006, Pluto was demoted as it did
not fulfill the latest criteria for the new
definition of the word “planet”.
Asteroids, Comets and Meteoroids
Asteroids are small
rocks similar to the
material that formed
the planets. They orbit
the sun too.
Most asteroids are
located between the
orbits of Mars and
Jupiter called asteroids
A comet us composed of dust and rock particles
mixed in with frozen water, methane and ammonia.
A comet circles the Sun in a very big elliptical orbit.
Some comets take thousands of years to orbit the
The most popular comet is Halley’s comet which
takes 76 years to orbit the Sun.
When a comet’s orbit take it close the Sun, the heat
from the Sun melts some of the ice. This creates a
hazy cloud that looks like a gigantic tail
Meteoroids are small rocky fragment of debris
floating through the space.
When the meteoroids float too near to Earth,
they will be pulled in by the force of Earth’s
Most of the meteoroids are so small that they are
completely vaporized in Earth’s atmosphere.
A meteoroids that burns up in Earth’s
atmosphere is called meteor, or commonly
known as shooting star.
If a meteoroids is large enough, it may not
completely burn up in the atmosphere. When it
hits Earth, its is called meteorite.
When a meteorite strikes on the surface of the
moon or planet, a hole is formed, called crater.
1. The Sun is a star located at the center
of our Solar System.
2. It is our nearest star and the engine
for all life on Earth.
3. The Sun contains 99.85% of all matter
in the Solar System.
Characteristics of the Sun
4. Our Sun is a medium-sized yellow star.
5. It is a huge, rotating ball of hot gas
with nuclear reactions that lights up
the Earth and provides us with heat
6. It is formed 4.5 billion years ago.
7. The characteristics of the Sun is the
summarized in the table below.
Distance from the Earth 149 680 000 km
Temperature of the Sun The surface temperature is
approximately 5500 ◦C. The
outer atmosphere of the Sun
is extremely hot, up to 1.5 to
2 million degrees.
Composition of the Sun Composed of about 76%
hydrogen and 22% helium.
Iron, nickel, silicon and
carbon make up the
remaining 2% by mass.
Radius (size) 109 times that of the Earth
Density 0.27 times that of the Earth
Mass 330 420 times that of the
The Sun has a four – part structure, from the inner core to
the outer corona. Each layer has its own characteristics
such as its temperature and density.
The center of the Sun is gaseous core. This is where the
nuclear reactions occur. The reactions produce a vast
amount of energy. The temperature at the core is about
15, 000,000 C.
The Structure of the Sun
(a) Photosphere is the visible surface of the Sun where
the Sun’s energy is seen as moving like boiling water.
(b) Photosphere produces the visible light we see and is
generally considered to be the surface of the Sun.
(c) It is one of the coolest layers of the Sun with
temperatures less than 6000 C.
(d) Large magnetic disturbance sometimes break through
he photosphere and cause sunspots.
(a) Just above the photosphere lies the chromosphere, a
red-glowing region of gas. It is considered to be part of the
(b) The temperature at the chromosphere is about 15
(c) The chromosphere is active with activity, mainly due to
the various magnetic fields. This causes various
phenomena such as sunspots, flares and prominences.
(d) The chromosphere can be seen by the naked eye
during a total solar eclipse.
(a) Above the chromosphere is the outermost, tenuous
atmosphere of the Sun, the corona.
(b) The corona is extremely hot. It has a temperature of
about 2 000 000 C.
(c) Prominences can remain relatively quiet and stable for
days and weeks, but when the magnetic fields that support
them change, they tend to erupt.
1. The Sun might look like an unchanging object in the sky,
yet many activities take place in it.
2. The Sun’s magnetic field controls the motion of the gases
in the corona, creating delicate streamers which is seen
from the Earth as flares and arching prominences.
3. Solar flares
(a) Solar flare is the explosive event in the solar surface.
It is the huge outburst of solar material which are
several thousand to million kilometers long.
Phenomena occurring at the surface of the Sun
(b) A flare may release an amount of energy equivalent to
100 million hydrogen bombs.
(a) Prominences are the masses of glowing gas above the
Sun’s bright surface. They are visible to the naked eye only
during total solar eclipses.
(b) They are suspended above the surface of the Sun by
loops of magnetic fields.
(c) Prominences can remain relatively quiet and stable for
days or weeks but when the magnetic fields that support
them change, they tend to erupt.
(d) Prominences are thousands to million of kilometers wide
(a) If we view the Sun’s image projected by telescope, we will
see one or more darker patches which are known as
(b) The spots are not genuinely black. They appear so
because they are cooler than the surrounding regions of the
(c) Spots generally appear in groups. Sunspots may
be huge, but they are not permanent.
(d) A major group of sunspots may last for six
months but the very small spots often have lifetimes
of less than a couple of hours
6. Solar wind is a flow of gases from the Sun that
disturbs and shakes the Earth’s magnetic field.
7. Solar flares often give off ultraviolet light and X-ray
that heat up the Earth’s upper atmosphere. This
“space weather” can change the orbits of the
satellites and shorten their lifetime.
8. The excessive radiation can physically damage the
satellites and pose a threat to astronauts. When the Earth’s
magnetic field is disturbed, it can also result in current
surges in power lines that destroy equipment and knock out
power over large areas.
9. Researchers suspect that long-term changes is solar
radiation cause substantial variations in the global climate.
For example, scientists have found a correlation between
low sunspot activity and severe Ethiopian droughts that
occurred over a period or more than four centuries.
1. Looking at the Sun improperly can harm your
eyes. Never watch the Sun with a telescope
or binoculars because the concentrated light
will turn your retina. Even staring at the Sun
for more than a couple of seconds can
damage your eyes.
2. Those who live at far northern and
southern latitudes on the Earth may
occasionally observe a spectacular light
show in the sky that is caused by solar
wind. Solar flares not only emit radiation
such as X-rays but also atomic particles.
When the strong solar wind distorts the
Earth’s magnetic field, it affects the
motion of charged particles. These
particles crash into the upper atmosphere,
exciting the gas atoms there and causing
them to glow. The glow can be seen from
the ground as aurora.
1. The Sun generates its energy by a nuclear reaction
called nuclear fusion.
2. The Sun is a powerful fusion reactor.
3. Fusion occurs at the center of the Sun.
4. At the Sun’s core, hydrogen atoms bang into each other
constantly and fuse into atoms of helium.
5. Energy is released when the nuclear reactions inside the
Sun convert hydrogen to helium.
Generation of energy
by the Sun
7. Every second, the sun converts about 4
million tons of hydrogen to helium and energy
and radiates it into space.
8. The Earth only intercepts one billionth of the
Sun’s light energy.
6. During the fusion process, a small amount of
energy mass is converted to a large amount
Stars and Galaxies
A star is a self- luminous gaseous body.
The Sun is an example of a star. It is a self-
luminous sphere of gas and plasma that is held
together by its own gravity and energized by
nuclear reactions in its interior.
Stars come in different sizes.
Type Size (relative to the diameter of the
Supergiant 100 to 1000 times bigger
Giant 10 to 100 times bigger
White dwarf 1000 times smaller
Types of Stars according to sizes
Stars also vary in brightness and colour
according to their approximate surface
Sirius and Rigel are examples of bright stars.
Classification of Stars
Colour Temperature Example
Blue > 25, 000 Spica
Bluish- white 11,000 – 25, 000 Rigel
White 7500 – 11, 000 Vega
Yellowish- white 6, 000 – 7, 500 Capella
Yellow 5, 000 – 6, 000 Sun
Orange 3, 500 – 5, 000 Arcturus
Red < 3,500 Antares
Constellation is a group of stars with a
pattern of maybe an animal or a
Most of the constellations were named
after animals or characters in ancient
Up to date, modern astronomers had
named 88 constellations.
Locating stars and constellations sky is
fascilitated by a star map it varies depending on
In order to use the star map effectively, you need
to know your latitude and longitude on the
surface of the Earth, and also the offset of your
timezone from Greenwich meridian.
The signs of zodiac are Aries, Taurus,
Gemini, Cancer, Leo, Virgo, Libra, Scorpio,
Sagittarius, Capricornus, Aquarius and
Formation of Stars
Stars are formed from nebulae.
Nebulae are clouds of gas and dust. They glow by
reflecting the light of nearby stars. Nebulae are
regarded as regions in which fresh stars are being
formed out of the interstellar material.
A star is born when enormous clouds of dust and
gas in a nebula collapse under the force of the
The collapse causes the cloud to spin
progressively faster and condenses the material
that makes up a nebula.
As these material is condensed and compressed
by the gravitational force, its temperature begins to
rise at its centre.
When the temperature has risen sufficiently,
nuclear fusion occurs in the core and energy in the
form of heat and light travels out from the centre. It
glows and turns into a star.
As long as there is still material within the star, the
nuclear fusion process can continue and the star
will continue to glow.
Death of Stars
The destruction of a star begins when it has
used up its core hydrogen fuel.
The core will shrink and heat up, whereas the
outer layers will expand and cool.
During this time, the star will turn into a red
giant. It is tens or even hundreds of times larger
For a medium- sized star like our Sun, its outer
layers will disperse into space. The core that is
left will become a white dwarf.
Giant stars will expand further to become
supergiants and blow up in a supernova explosion.
The star will end up as a neutron star.
For the very big stars, however they will become
The gravity around a black hole is so strong that
absolutely nothing, not even light, can escape.
The universe consists of everything that exists
around us. All matter and energy are part of the
There are millions of galaxies in our universe.
A galaxy is a system of stars. It is like an island in
space made up of gas, dust and millions of stars.
Our solar system is located in the Milky Way
Milky Way is a fairly large spiral galaxy. It consists
of about 200 billion stars with our own Sun being
one of them.
Galaxies come in various shapes, they can be
spiral, elliptical or irregular.
The existence of the Universe
We should be thankful for the existence of the
universe and appreciate the uniqueness, order,
beauty and harmony of the universe as a gift
The universe is so vast, nobody has seen the
edge of it. The Earth is less than a speck of dust
in the universe.
All that exists in the universe is not permanent.
Therefore, we should value our life and make it
The importance of the Sun
to life on Earth
There could be no life on Earth without the Sun.
The Sun is a source of light and heat for life on
Plants transform solar energy into chemical energy
stored in food through a process called
photosynthesis. Therefore, the Sun is that the
bottom of all food chains.
Modern humans use energy from the Sun as a
clean, inexpensive source of power in the form of
The Sun also serves as an important role in helping
us to understand the rest of the universe. It is the
only star close enough to us and serves as the key
in understanding other stars.
The importance of the Moon to life
The Earth has a large satellite which is called
The Moon is directly or indirectly influencing
the life on Earth.
The most obvious influence of the Moon on the
Earth is the ocean tides.
The regular rise and fall of sea level creates a
unique environment for life on Earth.
The Moon has also encourage the development of
intelligence of humans, specially in mathematics,
arts and sciences.
By observing changes in the Moon’s phase and
brightness, humans have developed the calendars.
It helps them to plan their life accordingly.
When Galileo turned his telescope towards the
Moon, it spurred the high technological development
in space exploration.