class 8 science textbook solutions

Stars and the Solar System – Class 8 Science Textbook Solution


Chapter 17 Stars and the Solar System


Choose the correct answer in s 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:
(а) 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:
1.    The planet which is farthest from the sun is _________
2.    The planet which appears reddish in colour is _________
3.    A group of stars that appear to form a pattern in the sky is known as a _________
4.    A celestial body that revolves around a planet is known as _________
5.    Shooting stars are actually not _________
6.    Asteroids are found between the orbits of _________ and _________
Answer:

1.    The planet which is farthest from the Sun is Neptune.
2.    The planet which appears reddish in colour is Mars.
3.    A group of stars that appear to form a pattern in the sky is known as a constellation.
4.    A celestial body that revolves around a planet is known as a satellite.
5.    Shooting stars are actually not stars.
6.    Asteroids are found between the orbits of Mars and Jupiter.
 

5. Mark the following statements is true (T) or false (F):
1.    Pole star is a member of the solar system. ( )
2.    Mercury is the smallest planet in the solar system. ( )
3.    Uranus is the farthest planet in our solar system. ( )
4.    INSAT is an artificial satellite. ( )
5.    There are nine planets in our solar system. ( )
6.    Constellation Orion can be seen only with the telescope. ( )
Answer:

1.    Pole star is a member of the solar system. (F)
2.    Mercury is the smallest planet in the solar system. (T)
3.    Uranus is the farthest planet in our solar system. (F)
4.    INSAT is an artificial satellite. (T)
5.    There are nine planets in our solar system. (F)
6.    Constellation Orion can be seen only with the telescope. (F)
 

6. Match items in Column A with one or more items of Column B:

 

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

8. Name the largest planet of the solar system.
Answer:
Jupiter.
 

9. What is a constellation? Name any two constellations.
Answer:
The stars forming a group that has a recognizable shape is called a constellation.
•    Ursa major
•    Orion
 

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

(a) Ursa major and
(b) Orion

11. Name two objects other than planets which are members of the solar system.
Answer:
Meteors and Asteroids.
 

12. Explain how you can locate the pole star with the help of Ursa Major.
Answer:
To locate the pole star we should look towards the northern part of the sky and identify Ursa Major. We may look at the two stars at the end of Ursa Major. A straight line passing through these stars is imagined and is extended towards the north direction. This line will lead to a star which is not too bright. This is the Pole star.
 

13. Do all the stars in the sky move? Explain.
Answer:
No, no star moves in the sky. They appear to move from east to west because the Earth rotates from west to east about its axis.
 

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 of stars is so large that it cannot be expressed in terms of kilometers. That is why very large distances are expressed in another unit known as light year. One light-year is the distance traveled by light in one year. If the distance of a star is eight light-years, it means that this distance is the distance travelled by light in eight years.
  

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:
If the radius of the Earth is r.
Then, the radius of Jupiter is 11r.
So, ratio of the volumes of Jupiter and the Earth is = 43π(11r)343πr3 = 1331 : 1
So, 1331 Earth can accommodate Jupiter.
 

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


Answer:

No, the sketch is not correct. The correct sketch is

 

Stars and the Solar System Additional s and Answers

 

1. Why the village sky was so different from the night sky in big cities?
Answer:
The village sky is fascinating because there is no bright light and the atmosphere is clear.
 

2. Do you find any star-like object which dies not twinkle?
Answer:
Yes, this object is a planet.
 

3. What are new moon day and full moon day?
Answer:
New moon day is the day when the moon is not visible to us. Full moon day is the day when the moon appears as a full circle.
 

4. What is the crescent moon?
Answer:
The next day after the new moon day, only a small part of the moon appears in the sky, which is called the crescent moon.
 

5. Why does Sun which is also a star appear so large compared to the other stars?
Answer:
The stars are million times farther away than the Sun. This means that Sun is nearest to the Earth. That is why the Sun appears so bright.
 

6. What is a light-year?
Answer:
Large distances expressed are expressed in a unit called year. It is the distance travelled by light in one year. The speed of light is about 300,000 km per second.
 

7. What is the Solar system?
Answer:
The Sun and the celestial bodies which revolve around it form the solar system.
 

8. What keeps objects revolving around Sun?
Answer:
The gravitational attraction between the Sun and objects keeps them revolving around it.
 

9. Name the star which is nearest to earth.
Answer:
Sun.
 

10. Draw the diagram of the solar system.
Answer:

11. Name the planet nearest to Sun.
Answer:
Mercury (Budh).
 

12. Why is it very difficult to observe it?
Answer:
It is very difficult to observe it because it is very close to the sun. Most of the time it is hidden in the glare of the sun.
 

13.
Name the planet which shows phases like the moon?
Answer:
Venus.
 

14. Name the planet which is the second planet in terms of its distance from the sun?
Answer:
Venus.
 

15. Name the plant in the solar system on which life is known to exist.
Answer:
Earth.
 

16. Why does life exist on earth?
Answer:
Some special environmental conditions are responsible for the existence and continuation of life on the Earth. These include just the right distance from the Sun so that it has the right temperature range, the presence of water and a suitable atmosphere, and a blanket of ozone.
 

17. Name the star which has a slightly reddish appearance.
Answer:
Mars.
 

18. What is the other name of Mars?
Answer:
Red Planet.
 

19. Name the largest planet.
Answer:
Jupiter.
 

20. Name the planet which has a maximum number of moons and how many moons it has?
Answer:
Saturn has a maximum number of moons. It has 30 moons.
 

21.
Name the outermost planets of the solar system.
Answer:
Uranus and Neptune.
 

22. What are asteroids?
Answer:
There is a large gap in between the orbits of Mars and Jupiter (Fig.). This gap is occupied by a large number of small objects that revolve around the Sun. These are called asteroids.
 

23. What are meteors?
Answer:
Meteors are very small stone-like objects revolving around the sun. They are seen as a bright streak of light that flashes for a moment across the sky.
 

24. What is the other name of meteors?
Answer:
Another name of meteors is Shooting Stars.
 

25. What are artificial satellites?
Answer:
Artificial satellites are man-made satellites revolving around the earth.
 

26. Mention the names of few artificial satellites.
Answer:
INSAT-3E, Kalpana Chawla-I, Sputnik-I, Aryabhatta, IRS, etc.

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