NCERT Solutions Class 8 Science
The NCERT Solutions in English Language for Class 8 Science Chapter – 17 (Stars and the Solar System) has been provided here to help the students in solving the questions from this exercise.
Chapter – 17 (Stars and the Solar System)
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 a 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. (False)
(b) Mercury is the smallest planet of the solar system. (True)
(c) Uranus is the farthest planet in the solar system. (False)
(d) INSAT is an artificial satellite. (True)
(e) There are nine planets in the solar system. (False)
(f) Constellation Orion can be seen only with a telescope. (False)
6. Match items in column A with one or more items in column B.
| A | 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 –
| A | B |
| (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 – The planet Venus is found in the western part of the sky after sunset and is said to be known as an evening star.
8. Name the largest planet of the solar system.
Answer – Jupiter is the largest planet of the solar system.
9. What is a constellation? Name any two constellations.
Answer – The group of stars that forms a recognisable pattern in the sky is known as a constellation. Two constellations are Ursa Major and Orion.
10. Draw sketches to show the relative positions of prominent stars in
(a) Ursa Major and
(b) Orion
Answer –
(a) Ursa Major – There are seven prominent & noticeable stars in this constellation. It appears like a big ladle where three stars form a handle & four stars form a bowl. It also appears like a question mark
(b) Orion – It is one of the most magnificent constellations in the sky. It also has seven or eight bright stars that appear like a hunter in the sky.
11. Name two objects other than planets which are members of the solar system.
Answer – Asteroids and Meteors are the members of the solar system other than planets.
Meteors – Meteors are small celestial objects that are seen as bright streaks of light in the sky. Due to the heat produced by the friction of the Earth’s atmosphere, the Meteors are burnt out while entering in, this causes the bright streaks in the sky. They are not planets.
Asteroids – The Asteroids are the collection of a huge number of small objects; gasses and dust revolving around the sun. Between the orbits of Mars and Jupiter, they occupy the large gap. These are not planets. They are the celestial bodies and are known as Asteroids.
12. Explain how you can locate the Pole Star with the help of Ursa Major.
Answer – Pole star is situated at the end of the Ursa Major. If a straight line starting from the last two stars is extended towards the north direction, it will lead to the Pole star.
13. Do all the stars in the sky move? Explain.
Answer – All the stars in the sky do not move, but they appear to move from east to west. This is actually due to the rotation of earth on its axis. Earth moves from west to east. So it appears as the stars are rising from east and as the day dawn they sets in the west.
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 – Stars are millions of kilometres away from the earth. It is not convenient to express such a large distance in the units of km. So the distance of stars from the earth is expressed in time taken by light to travel in one year. Eight light years means time taken by light to travel 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 – The volume of sphere = ℼr3
Let the radius of the earth be ‘r’
The radius of Jupiter = 11×r
The volume of earth = ℼr3
The volume of Jupiter = ℼ(11r)3
= ×
× (11r)3
Required ratio = Volume of the Jupiter / Volume of the Earth
= ×
× (11r)3 :
×
× r3
= 1331 : 1
The volume of Jupiter is 1331 times the volume of the earth. Thus, around 1331 earths can fit into one jupiter.
16. Boojho made the following sketch (Fig. 17.29) of the solar system. Is the sketch correct? If not, correct it.
Answer – No, the sketch is not correct because the positions of planets Mars and Venus are interchanged. And the positions of Uranus and Neptune are interchanged. Also, the Asteroid belt is shown in the gap between the orbits of Jupiter and Saturn which is not correct. The asteroid belt is located between the orbits of Mars and Jupiter. The correct fig is given below.
