Q: Answer the following questions briefly:
a) How does a planet differ from a star ?
Ans: The differences between a planet and a star are:
- Stars have their own light and heat while planets don’t have their own light and heat.
- Planets have satellites revolving around them while stars don’t have any satellites.
- There are 8 planets in our galaxy while stars are innumerable.
b) What is meant by the ‘Solar system’ ?
Ans: The sun, eight planets, satellites and some other celestial bodies known as asteroids and meteoroids form the ‘solar system’.
c) Name all the planets according to their distance from the sun.
Ans: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
d) Why is the Earth called a unique planet ?
Ans: Earth is called a unique planet because:
- Conditions favourable 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 essential for our survival.
- The air has life supporting gases like oxygen.
e) Why do we see only one side of the moon always ?
Ans: The moon moves around the sun in about 27 days. It takes exactly the same time to complete one spin. As a result, only one side of the moon is always visible to us.
f) What is the universe ?
Ans: The universe is made up of vast number of galaxies.