Question 1: Answer the following questions briefly.
(a) How does a planet differ from a star?
(b) What is meant by the ‘Solar System’?
(c) Name all the planets according to their distance from the sun.
(d) Why is the Earth called a unique planet?
(e) Why do we see only one side of the moon always?
(f) What is the Universe?
Answer:
(a)
| Star |
Planet |
|
Stars have their own heat and light. It is very big and hot ball of fire made up of gases. They twinkle because they give a large amount of heat and light. Stars are countless.
Example: Vega, Sirius etc.
|
Planets do not have their own heat and light. They receive
heat and light from the sun. They do not twinkle like the stars do. There are 8 planets in our solar system.
Example: Earth, Jupiter etc.
|
(b) The sun, eight planets, satellite and some celestial bodies (asteroids and meteoroids) are bounded together by gravitational energy in a pattern to form solar system. There are four inner planets and four outer planets in the solar system. Inner planets are closer to the sun and are small. They are Mercury, Venus, Earth and Mars. They are separated from the outer planets by the Asteroid belt. The outer planets are far away from sun and huge in size. They are Jupiter, Saturn, Uranus and Neptune. The smallest planet in our solar system Is Mercury and the largest one is Jupiter. Our solar system comes in Milky Way galaxy.
(c) There are 8 planets. The planets according to their distance from the sun are as follows:
1. Mercury: It is the closest planet to the sun and as well as the smallest planet. Its distance from the sun is about 57.9 million km.
2. Venus: It is the second closest planet to the sun. Its distance from the sun is about 108 million km away.
3. Earth: It is the third closest planet to the sun. Its distance from the sun is about 150 million km away.
4. Mars: It is the fourth closest planet to the sun. Its distance from the sun is about 228 million km away.
5. Jupiter: It is the fifth closest planet to the sun. Its distance from the sun is about 778.3 million km away.
6. Saturn: It is the third farthest planet from the sun. Its distance from the sun is about 1429.4 million km.
7. Uranus: It is the second farthest planet from the sun. Its distance from the sun is about 2871 million km.
8. Neptune: It is the farthest planet from the sun. Its distance from the sun is about 4504.3 million km away.
(d) Earth is called a unique planet because of following reasons:
1. It is the only planet where life exists. The air contains some life supporting gases like O 2 .
2. The temperature of the earth is neither too hot nor too cold. Conditions favorable to support life are probably found only on earth.
3. There is water present in the earth which is very essential for the survival. There are so many geographical features on Earth like volcanoes, islands, mountains, oceans, deserts, grasslands, forests etc.
4. Abundance of water makes the Earth which is also known as ‘blue planet’. The Earth is also the densest planet in the solar system.
(e) We only see one side of the moon because the moon takes 27 days to complete one orbit around the earth. It takes some time to spin once on its axis. The side of moon that faces the Earth is called ‘near side’ and the opposite one is known as ‘far side’.
(f) The vast expanse of space or the largest unit in which life exists is called Universe. It is infinite in volume. The three most common elements in universe are Hydrogen (H 2 ), Helium (He) and Oxygen (O 2 ). The universe is so dark that it is invisible and is also called as ‘dark matter’.
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