NCERT solutions for class 8 Science Chapter 17 Stars And The Solar System

Solution for Exercise

Q.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


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Answer :

(c) A constellation

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


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Answer :

(a) Sirius

Q.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.


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Answer :

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

Q.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 _________ .


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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__.

Q.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.


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Answer :

(a) False
(b) True
(c) False
(d) True
(e) False
(f) False

Q.6 Match items in column A with one or more items in column B.

Column A
(i) Inner planets
(ii) Outer planets
(iii) Constellation
(iv) Satellite of the Earth
Column B
(a) Saturn
(b) Pole star
(c) Great Bear
(d) Moon
(e) Earth
(f) Orion
(g) Mars


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Answer :

Column A
(i) Inner planets
(ii) Outer planets
(iii) Constellation
(iv) Satellite of the Earth
Column B
(g) Mars, (e) Earth
(a) Saturn
(c) Great Bear, Orion
(d) Moon

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


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Answer :

In west side of sky .

Q.8 Name the largest planet of the solar system.


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Answer :

Jupiter

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


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Answer :

A group of stars which has a recognizable shape is called a constellation.
Example: Ursa Major, Orion

Q.10 Draw sketches to show the relative positions of prominent stars in
(i) Ursa Major and
(ii) Orion


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Answer :

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


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Answer :

Comets and asteroids

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


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Answer :

In order to locate the Pole star in the sky, first of all Ursa Major or Big Dipper constellation must be located. The bowl of the Big Dipper consists of four bright stars (as shown in the given figure).

Consider two stars at the end of this bowl. Now, draw an imaginary straight line towards the Northern direction connecting these two stars (as shown in the given figure).

This imaginary line meets a star called the Pole Star. The length of the imaginary line from the bowl is about five times the distance between the two stars of the bowl.

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


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Answer :

No. The Earth rotates from West to East on its axis. Hence, all stars in the sky (except the Pole star) appear to move from East to West. With reference to the Earth, the Pole star does not appear to move in the sky because it is located above the axis of rotation of the Earth in the north direction. It appears to remain stationary at a point in the sky.

Q.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?


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Answer :

The distance of the stars from the Earth and the distance between the stars are very large. It is inconvenient to express these distances in kilometer (km). Thus, these large distances are expressed in light years. One light year is the distance travelled by light in one year. One light year is equal to 9.46 x 1012km.
A star is located eight light years away from the Earth. This means that the distance between the star and the Earth is equivalent to the distance travelled by light in eight years, i.e., a star is located 8 x (9.46 x 1012) = 7.6 x 1013km away from the Earth.

Q.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?


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Answer :

Let us consider Jupiter and Earth are two spheres with radii R and R’ respectively. Given in the question that radius of Jupiter is 11 times the radius of the Earth.
So, R’= 11R
Volume of sphere of radius r is given as = 4?3?r3
Volume of Earth = 4?3?r3
And, volume of Jupiter = ?(R1)3
=4?3 ?(R1)3=1331[4/3?R3]
The ratio of the volume of Jupiter and earth
=volume of Jupiter volume of Earth =1331(4/3?R3)4/3?R3=1331
Therefore, this ratio suggests that Jupiter can fit 1331 number of Earth in it.

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


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Answer :

No, the sketch made by Boojho is not correct. The correct sketch is given below:



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