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SAI INTERNATIONAL SCHOOL
Class 8
Lesson Notes
Subject-Physics
CH- Stars and Solar system
Subtopic- Constellations

 Light Year
 The distance between celestial objects is described in light years.
 A light year is defined as the distance traveled by light in one year.
 The speed of light = 300,000 km per second
 The distance between the sun and the earth = 8 light minutes
 The distance between Alpha Centauri and the earth = 4.3 light years
 The Stars
 The stars are celestial bodies comprising of hot gases (mainly helium and
hydrogen). All the stars emit their own light.
 All the stars are not the same. They may vary in brightness, size, colours and
temperature.
 The significance of the Pole Star
The pole star also called as Polaris is situated close to the earth's axis of
rotation. As a result, the position of the pole star appears to be fixed. This is unlike
the other stars as their position keeps on changing with respect to the earth.

 Constellations: A constellation is described as a group of stars that form a
recognizable shape or pattern.

Major Constellations