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
Sol. (c) A constellation

Q.2 Which of the following is not a planet of the sun?
(a) Sirius
(b) Mercury
(c) Saturn
(d) Earth
Sol. (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 moon’s surface.
(d) The thickness of the moon’s atmosphere is not constant.
Sol. (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 _________.
Sol. (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.                  ( )
Sol. (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)

Q.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
Sol.       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

Q.7 In which part of the sky can you find venus if it is visible as an evening star?
Sol. Venus is visible in the western horizon after sunset in the sky.

Q.8 Name the largest planet of the solar system.
Sol. The largest planet of the solar system is jupiter.

Q.9 What is a constellation? Name any two constellations.
Sol. The different known shapes that are formed by a group of stars is known as a constellation. Example: ursa major and orion.

Q.10 Draw sketches to show the relative positions of prominent stars in (a) Ursa major and (b) Orion.
Sol. The sketches are as follows:
(a) Ursa major:(b) Orion:

Q.11 Name two objects other than planets which are members of the solar system.
Sol. The two objects other than planets which are members of the solar system are comets and asteroids.

Q.12 Explain how you can locate the pole star with the help of ursa major.
Sol. To find the location of pole star with the help of ursa major, consider the two stars at the end of the bowl of ursa major. Now, draw an imaginary straight line in northern direction connecting these two stars. The imaginary line would meet a star known as pole star. The distance of pole star is around five times away from the bowl.

Q.13 Do all the stars in the sky move? Explain.
Sol. No, all the stars do not move. The movement of all stars in the sky is from east to west except pole star. With respect to earth, the pole star looks stationary because it is located above the axis of rotation of the earth in the north direction.

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?
Sol. The distance in-between stars and between earth and stars are in range of millions of kilometres. So, these distances cannot be expressed in kilometres; hence, distance between stars is expressed in light years.
One light year is the distance travelled by light in one year. One light year is equal to 9.46 × 10¹² km.
A star located at eight light years away from earth means that the distance between the star and the earth is equal to the distance travelled by light in years. In figures, eight light years will be equal to 8 x 9.46 × 10¹² km = 7.6 × 10¹³ km.

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 accomodate?
Sol. Given that the radius of jupiter is 11 times the radius of the earth. Suppose the radius of earth be r, then the radius of the jupiter will be 11r.
Therefore, ratio of volumes of jupiter and earth = (volume of jupiter)/(volume of earth)
= (4/3 π (11r³))/ (4/3 π (r³))
= 1331/1
= 1331:1
Hence, jupiter can accommodate 1331 number of earths.

Q.16 Boojho made the following sketch (fig.) Of the solar system. Is the sketch correct? If not, correct it.Sol. The sketch made by boojho is not correct because the position of mars, venus, uranus and neptune are wrong. The position of mars & venus and uranus & neptune should be interchanged. The correct sketch is as shown below: