Chapter 17 Stars and the Solar System

Class 8 Science Chapter 17 |
Stars and the solar System NCERT Solutions

Choose the correct answer in Questions 1-3.
1. Which of the following is NOT a member of the solar system?
(a) An asteroid              (b) A satellite
(c) A constellation          (d) A comet

Answer: (c) A constellation

2. Which of the following is NOT a planet of the sun?
(a) Sirius                     (b) Mercury
(c) Saturn                    (d) Earth

Answer: (a) Sirius

3. Phases of the moon occur because
(a) we can see only that part of the moon which reflects light
towards us.
(b) our distance from the moon keeps changing.
(c) the shadow of the Earth covers only a part of the moon’s surface.
(d) the thickness of the moon’s atmosphere is not constant.

Answer: (a) we can see only that part of the moon which reflects light
towards us.

4. Fill in the blanks.
(a) The planet which is farthest from the Sun is ____________ .
(b) The planet which appears reddish in colour is ____________ .
(c) A group of stars that appear to form a pattern in the sky is known as a __________.
(d) A celestial body that revolves around a planet is known as __________.
(e) Shooting stars are actually not ____________.
(f) Asteroids are found between the orbits of _________ and _________ .

Answer:

(a) The planet which is farthest from the Sun is Neptune .
(b) The planet which appears reddish in colour is Mars.
(c) A group of stars that appear to form a pattern in the sky is known as  Constellation.
(d) A celestial body that revolves around a planet is known as satellite.
(e) Shooting stars are actually not stars.
(f) Asteroids are found between the orbits of Mars and Jupiter .

5. Mark the following statements as true (T) or false (F).
(a) Pole star is a member of the solar system. ( )
(b) Mercury is the smallest planet of the solar system. ( )
(c) Uranus is the farthest planet in the solar system. ( )
(d) INSAT is an artificial satellite. ( )
(e) There are nine planets in the solar system. ( )
(f) Constellation Orion can be seen only with a telescope. ( )

Answer:
(a) Pole star is a member of the solar system. (F)
(b) Mercury is the smallest planet of the solar system. (T)
(c) Uranus is the farthest planet in the solar system. (F)
(d) INSAT is an artificial satellite. (T)
(e) There are nine planets in the solar system. (F)
(f) Constellation Orion can be seen only with a telescope. (F)

6. Match items in column A with one or more items in column B.
Column A                             Column B
(i) Inner planets                   (a) Saturn
(ii) Outer planets                  (b) Pole star
(iii) Constellation                  (c) Great Bear
(iv) Satellite of the Earth     (d) Moon
                                                  (e) Earth
                                                  (f) Orion
                                                 (g) Mars

Answer:
(i) Inner planets                  (g) Mars (e) Earth
(ii) Outer planets                 (a) Saturn
(iii) Constellation                 (c) Great Bear (f) Orion
(iv) Satellite of the Earth      (d) Moon

7. In which part of the sky can you find Venus if it is visible as an evening star?

Answer:
Venus appears in the western horizon.It becomes visible after sunset and that is why called as evening star.

8. Name the largest planet of the solar system.

Answer:
Jupiter is the largest planet of solar system.

9. What is a constellation? Name any two constellations.

Answer:
A constellation is defined as group of stars that form an imaginary recognisable pattern.

For ex: Ursa major and Orion

10. Draw sketches to show the relative positions of prominent stars in
(a) Ursa Major and (b) Orion

Answer: Ursa Major

Orion

11. Name two objects other than planets which are members of the solar system.

Answer: Asteroids and Meteors

12. Explain how you can locate the Pole Star with the help of Ursa Major.

Answer:
To locate pole star in the sky, first of all Ursa major has to be located.Consider two stars at the end of the bowl. Draw an imaginary straight line towards the northern direction.Connecting these two stars.This imaginary line will meet at Pole star.The length of the imaginary line will be about five times the distance between the two stars of bowl.

13. Do all the stars in the sky move? Explain.

Answer:
The earth rotates from west to east on its axis. All stars in the sky appears to move from east to west. But the pole star does not appear to move in the sky because it is located above the axis of rotation of earth.

14. Why is the distance between stars expressed in light years? What do you
understand by the statement that a star is eight light years away from the Earth?

Answer:
The distance between stars and earth is million of kilometers. Thus these large distances are expressed in light year. One light year is equal to 9.46 ×10¹² Km. It is the distance travelled by light in one year. A star is 8 light years away from earth means that the distance between the star and earth is equivalent to distance travelled by light in eight years i.e. a star is located 8 × ( 9.46 ×10¹²) = 7.6 × 10¹³km away from the earth.

15. The radius of Jupiter is 11 times the radius of the Earth. Calculate the ratio of the volumes of Jupiter and the Earth. How many Earths can Jupiter accommodate?

Answer:
Radius of Earth = R

The radius of Jupiter=R’

The radius of Jupiter is 11 times the radius of earth.

Volume of Earth= 4/3 π R³

Volume of Jupiter = 4/3 π (R’)³

= 4/3 π (11R)³

= 1331( 4/3 π R³)

Ratio of Volume of Jupiter and earth= 1331:1

So Jupiter can accomodate 1331 Earth.

16. Boojho made the following sketch (Fig. 17.29) of the solar system. Is the
sketch correct? If not, correct it.

Answer :
Boojho’s sketch of the solar system is not correct because he has interchanged the position of Mars and Venus and also the position of Uranus and Neptune.