The sun, eight
planets, satellites and some other celestial bodies known as asteroids and
meteoroids form the solar system. We often call it a solar family, with the sun
as its Head.
The Sun
The sun is the
centre of the solar system. It is huge and made up of extremely hot gases. It
provides the pulling force that binds the solar system. The sun is the ultimate
source of heat and light for the solar system. The sun is about 150 million km
away from the earth.
Planets
There are eight
planets in our solar system. In order of their distance from the sun, they are:
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
All the eight planets of the solar
system move around the sun in fixed paths. These paths are elongated. They are
called orbits. Mercury is nearest to the sun. It takes only about
88 days to complete one round along its orbit. Venus is considered as
‘Earths-twin’ because its size and shape are very much similar to that of the
earth.
Till recently (August 2006), Pluto
was also considered a planet. However, in a meeting of the International
Astronomical Union, a decision was taken that Pluto like other celestial
objects discovered in recent past may be called “dwarf planets”.
The Earth
The earth is
the third nearest planet to the sun. In size, it is the fifth largest planet.
It is slightly flattened at the poles. That is why, its shape is described as a
Geoid. Geoid means an earth-like
shape.
Conditions favorable to support life
are probably found only on the earth. The earth is neither too hot nor too
cold. It has water and air, which are very essential for our survival. The air
has life-supporting gases like oxygen.
From the outer space, the earth
appears blue because its two-thirds (about 71%) surface is covered by water. It
is therefore, called a blue planet.
The Moon
Our earth has only
one satellite, that is, moon. Its diameter is only one-quarter that of
the earth. It appears so big because it is nearer to our planet than other
celestial bodies. It is about 3,84,400 km away from us.
The moon moves around the earth in
about 27 days. It takes exactly the same time to complete one spin. As a
result, only one side of the moon is visible to us on the earth. The moon does
not have conditions favorable for life. It has neither water nor air.
Asteroids
Apart from the stars, planets and satellites,
there are numerous tiny bodies which also which also move around the sun. These
bodies are called asteroids. They are found between the orbits of
Mars and Jupiter.
Meteoroids
The small pieces of
rocks which move around the sun are called meteoroids.
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