Page 185 - Science Class 08

Some other important facts about the sun:
1. Name the celes al bodies you can see in
the night sky without using telescope.
2. What is a telescope?
3. What is astrology?
4. What is astronomy?
5. What is Andromeda?
6. In which galaxy does our solar system
exist?
7. Why do stars appear twinkling?
8. What do you mean by constella on?
9. Why is the constella on Orion also called
the hunter?
THE SOLAR SYSTEM
The solar system is referred to the family of sun
which include eight planets and their satellites.
These planets are— Mercury, Venus, Earth,
Mars, Jupiter, Saturn, Uranus and Neptune. Till
a few years back Pluto was also considered as a
planet. But, in 2006 scien sts decided that
Pluto is too small to be called a planet.
Uranus
Saturn Neptune
Jupiter
Mars
Sun
Venus
Earth
Mercury
It is now considered as a ‘dwarf planet’.
Let’s study about the solar system in detail:
The Sun
Since our sun is a star, it is also made up of hot
glowing gases. It is at the centre of the solar
system. It contains 99 percent of ma er in the
solar system. It is about 150,000,000 km away
from Earth. The sun also rotates in its axis.
Science-8
v The sun is composed by several different
regions. But, we can see only its three
outer regions. These regions made up the
sun’s atmosphere.
v The photosphere is the innermost layer of
the atmosphere. It is the layer you see when
you look at the sun. Most of the light that
reaches the earth comes from this layer.
v The chromosphere is the middle layer of
the atmosphere. It is visible during total
solar eclipse.
v The outermost layer of the sun, the corona
is visible during a total solar eclipse. The
corona extends from about 2500 km above
the photosphere to beyond the earth’s
orbit.
v Nuclear fusion reac ons occur in the core
of the sun. Temperature in the core rises up
to 15 million °C. The energy produced in
the fusion reac ons moves out of the core
by radia on and conven on.
v The sun is about 1.4 million kilometres in
diameter. This is about 110 mes the
diameter of the earth.
v The temperature at the surface of the sun
is about 6000 °C.
The Planets
There are eight planets in our solar system
(Pluto has been excluded from the list of
planets). On the basis of the distances from the
sun, planets have been divided into two
groups. The four nearest planets to the sun like
Mercury, Venus, Earth and Mars have been put
in a group called inner planets. These planets
receive substan al amount of solar radia on.
The other four planets are very far away from
the sun. These planets are called outer planets.
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