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The Solar System
1. The Sun

How much do you know about this giant ball of energy in the sky?
Yes, we are talking about the sun. The sun is a star, a hot ball of glowing gases, mainly of
hydrogen and helium in the heart of our solar system. Our sun is the only source of light and
heat without which we would not be able to live. All the lives on the earth depend on the
energy that comes from the sun. It controls our climate and weather. The sun is the nearest
star to the earth. It is about 150 million km away from the earth. Weight of the sun is 3,00,000
times of the earth’s weight. The temperature at the surface of the sun is about 6000°C while
at the centre of the sun, it is about 15,000,000°C (15 million°C). The sun is the centre of our
solar system. All the planets revolve around it.

2. PlaneTS
The word planet has been derived from the Greek word The moon is the only place in
‘planetai’ meaning ‘wanderers’. They are heavenly our solar system, other than

bodies which revolve around the sun in an orbit. They do earth, where humans have
visited. On July 29, 1969,
not have their own heat and light. They shine merely by astronauts Neil Armstrong and
the reflection of the sun light. They are made up of solid Edwin Aldrin landed the Lunar
materials. While revolving around the sun, the planets Module of Apollo 11 on the
also rotate on their own axis. moon’s surface.

1. The Mercury : It is the closest planet to the sun. It is the smallest planet in the solar
system. Its day temperature is about 400°C and night temperature is –70°C. It has no
moon.

2. The Venus : It is the second planet from the sun. It is very hot. It is also called evening
star or morning star, so it is known as the jewel of the sky. It is very similar to the
Earth, so it is called Earth’s sister. It has no moon and rotates from east to west. It is
named after the Roman goddess of love and beauty.

3. The Earth : The earth is the third planet from the sun. It is the fifth largest planet in our
solar system. It is a unique planet because life is known to exist only on this planet. It
is spherical in shape, but slightly flattened at the poles, so scientists have described it

6 Social Studies-6