NCERT Solutions For Class 8 Science Chapter – 17
Q1. Which of the following is NOT a member of the solar system?
- An asteroid
- A satellite
- A constellation
- A comet
Answer:-
©Constellation
Q2. Which of the following is Not a planet of the sun?
- Sirius
- Mercury
- Saturn
- Earth
Answer:-
- Sirius
Q3. Phases of the moon occur because
- We can see only that part of the moon which reflects light towards us.
- Our distance from the moon keeps changing.
- The shadow of the Earth covers a only part of the moon surface
- The thickness of the moons atmosphere is not constant.
Answer:-
- Phases of the moon occur because we can see only that part of the moon which reflects light towards us.
Q4. Fill in the blanks:
- The planet which is farthest from the sun is _______.
- The planet which appears reddish in colour is _________.
- A group of stars that appear to form a pattern in the sky is known as a _______.
- A celestial body that revolves around a planet is known as a _________.
- Shooting stars are actually not _________.
- Asteroids are found between the orbits of ______ and _______.
Answer:-
- Mars
- Constellation
- Satellite
- Stars
- Mars Jupiter.
Q5. Mark the following statements as True or False.
- Pole star is a member of the solar system.
- Mercury is the smallest planet of the solar system.
- Uranus is the farthest planet in the solar system.
- INSAT is an artificial satellite.
- There are nine planets in the solar system.
- Constellation Orion can be seen only with a telescope
Answer:-
- False
- True
- False
- True
- False
- False
Q6. Match items n column A with one or more items in column B.
| A | B |
| (i) Inner plants | (a) Saturn |
| (ii) Outer plants | (b) Pole star |
| (iii) Constellations | ( c) Great Bear |
| (iv) Satellite of the Earth | ( d) Moon |
| ( e) Earth | |
| ( f) Orion | |
| ( g) Mars |
Answer:-
| A | B |
| (i) Inner planets | ( g) , ( e) Mars , Earth |
| (ii) Outer planets | ( a) Saturn |
| (iii) Constellations | ( c) ,( f) Great Bear, Orion |
| (iv) Satellite of the Earth | ( d) Moon |
Q7. In which part of the sky can you find Venus if it is visible as an evening star?
Answer:-
Venus appears in the western sky after sunset and is called the evening star.
Q8. Name the largest planet of the solar system.
Answer:-
The largest planet of the solar system is Jupiter.
Q9. What is constellations ? Name any two constellations.
Answer:-
A constellations is a group of stars that form a recognisable pattern in the sky. The two well known constellations are Ursa major and Orion
Q10. Draw sketches to show the relative position of prominent stars in (a) Ursa Major and (b) Orion
Answer:-
a) Orion seems to be like a hunter. The three bright stars appear in the belt, while four bright stars are arranged in the form of a quadrilateral.
(b) Ursa Major seems to be like a big dipper. There are four stars in the bowl of the dipper and three bright stars in the handle.
Q11. Name any two objects than planets which are members of the solar system.
Answer:-
- Asteroids
A collection of a large number of small objects,gases and dust are revolving around the sun. They occupy a large gap between the orbits of Mars and Jupiter. However, these are not planets These celestial objects are known as asteroids.
- Meteors
Meteors are small celestial objects that are seen as brights steaks of light in the sky . They burnt out on entering the Earth atmosphere because of the heat produced by friction. This results in bright streaks in the sky. They are not planets.
Q12. Explain how you can locate the Pole star with the help of Ursa Major.
Answer:-
For locating the pole stars in the sky first the big dipper or the Ursa Major constellations must be found The bowl of the big dipper consists of the four right stars.
Imagine the two stars at the end of this bowl. Then make an imaginary straight line towards the northern direction connecting these two stars.
This imaginary lines meets a star a called the Pole star The length of the imaginary line from the bowl is about five times the is distance between the two stars of the bowl.
Q13. Do all the stars in the sky move? Explain.
Answer:-
No. Earth rotates from West to East on its axis. Hence all the stars in the sky appear to move from East to West. With reference to the Earth, the pole does not appear to move in the sky because it is located above the x – axis of rotation of the Earth in the north direction. It appears to remain stationary at a point in the sky.
Q14. 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 the stars from the Earth and the distance between the stars are very large. It is inconvenient to express these distances in Kilometers 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 t 9.46 x 1012 km.
A star is located eight light years away from Earth. This means that the distance between the star and the Earth is equivalent to the distance travelled by light in eight years A star is located 8 x (9.46 x 1012) = 7.6 x 1013 km away from the Earth.
Q15. 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:-
Earth and Jupiter can be considered as two spheres with radii R and R’ respectively. Given that the radius of Jupiter is 11 times the radius of the Earth.
Thus, R’ = 11R
Volume of a sphere of radius r is given as = 4/3 ∏r3
Volume of Jupiter = 1331
The ratio of the volumes of Jupiter and Earth
= Volume of Earth/Volume of Jupiter
= 1331
Hence, this ratio suggests that Jupiter can accommodate 1331 number of Earths within it.
Q16. Boojho made the following sketch of the solar system Is the sketch correct ? If not correct it.
Answer:-
Planets of the solar system in sequence of their distances from the sun are: Mercury, Venus , Earth , MARS , JUPITER , Saturn , Uranus, and Neptune Therefore Boojho sketch of the solar system is not correct because he has interchanged the positions of Mars and Venus and also the positions of Uranus and Neptune Also he has shown the Asteroid belt in the gap between the orbits of Jupiter and Saturn This is not correct The asteroid belt is located between the orbits of Mars and Jupiter. The correct sketch of the solar system is shown in the given figure.
