Choose the correct answer in Questions 1-3.
Question 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
Solution 1.
(c) A constellation
Question 2. Which of the following is NOT a planet of the sun?
(a) Sirius
(b) Mercury
(c) Saturn
(d) Earth
Solution 2.
(a) Sirius
Question 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.
Solution 3.
(a) we can see only that part of the moon which reflects light towards us.
Question 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 _________ .
Solution 4.
(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 a satellite.
(e) Shooting stars are actually not stars.
(f) Asteroids are found between the orbits of Mars and Jupiter.
Question 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. ( )
Solution 5.
(a) Pole star is a member of the solar system. False
(b) Mercury is the smallest planet in 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
Question 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 |
Solution 6.
| 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 |
Question 7. In which part of the sky can you find Venus if it is visible as an evening star?
Solution 7. In the western part of the sky after sunset Venus is visible as an evening star.
Question 8. Name the largest planet in the solar system.
Solution 8. The largest planet in the solar system is Jupiter.
Question 9. What is a constellation? Name any two constellations.
Solution 9. A group of stars that form a definite pattern in the sky is called a constellation.
Two constellations are: Ursa Major and Orion
Question 10. Draw sketches to show the relative positions of prominent stars in (a) Ursa Major and (b) Orion
Solution 10.
- a) Orion is also known as the hunter. The middle three stars look like the belt of the hunter while a quadrilateral is formed by the four bright stars.
- b) Ursa Major looks like a big dipper. Ursa major consists of seven stars it looks like a ladle. The handle of the ladle has three stars and the bow has four stars.
Question 11. Name two objects other than planets which are members of the solar system.
Solution 11.
- Meteors
Some small objects enter the earth’s atmosphere with a high speed and evaporate because it gets heated by the friction due to the atmosphere. These small objects are commonly known as shooting stars but they are meteors.
2. Asteroids
There is a belt of small objects between mars and Jupiter. These small objects revolve around the sun and are known as asteroids.
Question 12. Explain how you can locate the Pole Star with the help of Ursa Major.
Solution 12. Ursa major consists of seven stars it looks like a ladle. The handle of the ladle has three stars and the bow has four stars.
If we extend the imaginary straight line passing through the last two stars of the Ursa major to about five times the distance between these two stars this extended line will lead to the pole star. The pole star does not move from its place.
If we extend the imaginary straight line passing through the last two stars of the Ursa major to about five times the distance between these two stars this extended line will lead to the pole star. The pole star does not move from its place.
Question 13. Do all the stars in the sky move? Explain.
Solution 13. No, none of the stars moves from their place. Our earth rotates on its axis from west to east which is why all the stars seem to move from west to east. The Pole star does not seem to move because it is situated above the axis of rotation of the Earth in the north direction.
Question 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?
Solution 14. The distances which are very huge are expressed as the light years which is why the distance between stars is expressed in light years.
A star is eight light-years away from the Earth means the distance between the earth and the star is equal to the distance travelled by the light in eight years, i.e., the distance of the star is 8 x (9.6 x 1012) = 7.6 x 1013 km away from Earth.
Question 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?
Solution 15.
Let us consider Jupiter and Earth are two spheres with radii R and R,’ respectively. Given in the question that the radius of Jupiter is 11 times the radius of the Earth.
So, R’= 11R
The volume of a sphere of radius r is given as = 4⁄3πr3
The volume of Earth = 4⁄3πr3
And, the volume of Jupiter = π(R1)3
=4⁄3 π(R1)3=1331[4/3πR3]
The ratio of the volume of Jupiter and Earth
=volume of Jupiter volume of Earth =1331(4/3πR3)4/3πR3=1331
Therefore, this ratio suggests that Jupiter can fit 1331 Earth in it.
Question 16. Boojho made the following sketch (Fig. 17.29) of the solar system. Is the sketch correct? If not, correct it.
Solution 16. No, the diagram is not correct because the correct sequence of the planets in the solar system is Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. The place of the asteroid belt is in between Jupiter and mars. This diagram depicts the wrong place of the asteroid belt. The correct diagram of the solar system is given below:
