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Looking up into the sky at night you can see many stars and
other objects. Early mariners used the stars for navigation. Today we know much
more about the stars, planets, Sun, moon and other objects in our sky. Stars
change over time. It may take millions to billions of years for a star to live
out its life. That is a very, very long time! Stars are formed initially from
gas and dust. They are composed mainly of the hydrogen gas. They are very hot
and give off huge amounts of energy in the form of heat and light.
Our Sun is a medium sized star and has a life span of about 10 billion years, after which it will cease to exist. Stars are very
far away from the Earth. The closest Star is about 23.5 trillion miles away.
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| Stars are contained in galaxies. A galaxy contains not only
stars, but clouds of gas and dust. There are billions of stars in the sky, which
are far away from the Earth. You can see the stars as twinkling dots of light in the
sky. Almost 2000 stars can be seen with your eyes and more stars can be seen
with binoculars and telescopes. A star is a big ball of gas, which gives off
both heat and light. |
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| Why do stars twinkle? Light comes from the stars in straight lines. When light comes to the Earth, it
passes through layers of air that form the Earths' atmosphere. The air makes
the light bent many times and in random directions. We will see the stars
twinkling, when the light bends from the stars as it goes through the air. |
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| Why can we see the sun but seldom
see the stars during the daytime? Stars are always in the sky. Our
sun makes so much light, it hides the other stars in the day time. At night,
when the sun is not there in our part of the sky, we can see the other stars. |
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The Stars you see at night are very much like the Sun,
but they are very far away. Hence, they appear to be smaller than the Sun.
Stars appear in groups and single. A group of stars forms a constellation.
You see different constellations at different times of the year. People in
different parts of the world assumed different shapes and gave them
different names.
One of the numerous constellations that we see in the
night sky is the Big Dipper or the Great Bear; it is made up
of 7 stars. Four stars form a quadrilateral, to form the body of the bear
and 3 stars form the tail. These star patterns appear to move across the sky
as the Earth rotates. As the Earth revolves around the Sun, you see these
star patterns in different parts of the sky.
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In spring the big dipper
is high in the sky and looks upside
down.
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In summer the big dipper
moves down with its
handle pointing up.
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In autumn the big dipper
is low and looks as if it can hold
water. |
In winter the big dipper
has moved up with its handle
pointing down. |
