The Earth in the Solar System

Celestial Bodies

• The Sun, the Moon and all other objects shining in the night sky are called Celestial Bodies.
• The moon, stars and planets cannot be seen during the daytime because the very bright light of the Sun does not allow us to see them.

Stars

• Stars are celestial bodies that are very big and hot. They are made up of gases. They have their own heat and light, which they emit in large amounts. The Sun is also a star.
• Constellations are various patterns formed by different groups of stars. For example, Ursa Major or Big Bear.
• The North Star indicates the north direction. It is also called the Pole Star. It always remains in the same position in the sky. We can locate the Pole Star with the help of Saptarishi.

The Solar System

The Sun, eight planets, satellites and some other celestial bodies known as asteroids and meteoroids form the Solar System.

The Sun

• The Sun is in the centre of the solar system. It is huge and made up of extremely hot gases.
• It provides the pulling force that binds the solar system.
• It is the ultimate source of heat and light for the solar system.

Planets

• Planets are celestial bodies that do not have their own heat and light. They are lit by the light of the stars.
• Earth is a planet too. It gets all its heat and light from the Sun, our nearest star.
• There are eight planets in our Solar System – Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

The Earth

• It is the fifth largest planet by size and is slightly flattened at the poles.
• Its shape is described as a Geoid which means an Earth-like shape.

→ Conditions favourable to support life are probably found only on the earth.

→ It is neither too hot nor too cold.

→ It has water and air, which are very essential for our survival.

→ The air has life supporting gases like oxygen.

• From the outer space, the Earth appears blue because its two-thirds surface is covered by water. It is, therefore, called a blue planet.

Satellite

• It is a celestial body that moves around the planets in the same way as the planets move around the sun.
• A human-made satellite is an artificial body designed by scientists to gather information about the universe or for communication.
• It is carried by rocket and placed in the orbit around the Earth.

The Moon

• The Moon is a satellite and moves around the Earth.
• The only satellite of Earth.
• Its diameter is only one-quarter that of the Earth.
• It appears so big because it is nearer to Earth than other celestial bodies.
• It moves around the Earth in about 27 days and takes exactly the same time to complete one spin. Hence, only one side of the moon is visible to us on the earth.
• It has mountains, plains and depressions on its surface.
• The moon appears at different times, in different shapes and at different positions.

→ The Full Moon can be seen only once in about a month’s time on the Full Moon night or Poornima.

→ A fortnight later, it cannot be seen at all. It is the New Moon night or Amavasya.

Asteroids

• These are numerous tiny bodies which also move around the Sun like stars, planets and satellites.
• They are found between the orbits of Mars and Jupiter.

Meteoroids

• These are small pieces of rocks which move around the Sun.
• Sometimes they come near the Earth and tend to drop upon it.
• During this process, due to friction with the air, they get heated up and burn, causing a flash of light.
• Sometimes, a meteor without being completely burnt falls on the earth and creates a hollow.

Galaxy

• It is a huge system of billions of stars, and clouds of dust and gases.
• Our Solar System is a part of the Milky Way galaxy.
• Millions of such galaxies make up the Universe.

MCQs

1. Which of the following is a natural satellite?

(a) IRSA

(b) EDUSAT

(c) Moon

(d) INSAT-I

► (c) Moon

2. Asteroids are found between the orbit of______

(a) Mars and Venus

(b) Mars and Mercury

(c) Mars and Saturn

(d) Mars and Jupiter

► (d) Mars and Jupiter

3. ____ is the closest celestial body to our earth.

(a) Earth

(b) Galaxy

(c) Moon

(d) Planet

► (c) Moon

4. What is the largest Planet in the Solar System?

(a) Venus

(b) Mercury

(c) Earth

(d) Jupiter

► (d) Jupiter

5. Why is the earth called as Blue Planet?

(a) Air colour is blue

(b) Land colour is blue

(c) Building having blue colour

(d) Two-third surface is covered by water

► (d) Two-third surface is covered by water

6. Stars appear to move from

(a) West to east

(b) East to west

(c) North to south

(d) South to west

► (b) East to west

7. All the planets move around the sun in an _________

(a) Rectangular path

(b) Straight path

(c) Elliptical path

(d) Circular path

► (c) Elliptical path

8. A huge system of stars is called _______

(a) Moon

(b) Earth

(c) Galaxy

(d) Planet

► (c) Galaxy

9. Which is the nearest star to the earth

(a) Mercury

(b) Moon

(c) Venus

(d) Sun

► (d) Sun

10. How many days does it take the earth to revolve around the sun?

(a) 120

(b) 365 (1/4)

(c) 20

(d) 541

► (b) 365 (1/4)

11. Which is the brightest planet in the universe?

(a) Mercury

(b) Venus

(c) Earth

(d) Saturn

► (b) Venus

12. The polar star indicates to which direction?

(a) North

(b) East

(c) South

(d) West

► (a) North

13. Which is the closest planet to the Sun

(a) Earth

(b) Venus

(c) Mars

(d) Mercury

► (d) Mercury

14. The planet known as the Earth twin is________

(a) Mars

(b) Saturn

(c) Venus

(d) Mercury

► (c) Venus

15. Which star is the head of the solar system

(a) Earth

(b) Moon

(c) Sun

(d) Big bear

► (c) Sun

16. How many planets are there in our solar system?

(a) Five

(b) Eight

(c) Six

(d) Nine

► (b) Eight

17. Moon appears big because

(a) It is very big than the earth

(b) It is bigger than the sun

(c) It is near to the earth

(d) It is far away from the earth

► (c) It is near to the earth

18. The three quarters of Sun is made up of

(a) Methane

(b) Magnesium

(c) Hydrogen

(d) Water

► (c) Hydrogen