### Stars and the Solar System - Exemplar Solutions 4

CBSE Class 8 Science
NCERT Exemplar Solutions
CHAPTER – 17
STARS AND SOLAR SYSTEM

19. Suppose the moon emits light of its own. Would it still have phases ? Justify your answer.
Ans: No, the phases are seen because the moon does not emit its own light and reflects the light of sun falling on its surface. Only that particular part of the moon is visible to us whose reflected light reaches us.

20. Fig. 17.6 shows comets without their tail. Show the tails of the comets at position A, B, and C. In which position, will the tail be longest ?
Ans: A comet appears generally as a bright head with a long tail that grows in size as it approaches close to sun. Therefore, at position B its tail will be long. The tail of the comet always points away from the sun.

21. Explain why we always see the same side of moon.
Ans: We always see the same side of moon because the period of rotation of the moon on its axis is equal to the period of its revolution round the earth.

22. Look at Fig. 17.7 carefully and answer the following question :
(a) In which part of the sky would you see the full moon in the evening ?
(b) In which part of the sky would you see the crescent moon in the evening ?
Ans: (a) We see the full moon in the evening in the eastern part of the sky.
(b) We see crescent moon in the evening in the western part of the sky.

23. Write the names of all planets in Fig. 17.8.
Ans:

24. Suppose the distance between earth and sun becomes half of its present distance. What is likely to happen to life ?
Ans: The sun continuously emits huge amounts of heat and light and acts as the sources of almost all energy on the Earth. If the sun gets closer to earth the survival won’t be possible due to excessive heat from sun. Life would no longer exist on earth.

25. Explain with a diagram how you can locate pole star with the help of the constellation Great Bear (Ursa Major).
Ans: Locate the two end stars of Ursa Major. Imagine a straight line passing through these stars as shown in the figure below. Extend this imaginary line towards the north direction. This line will lead to a star which is not too bright. This is pole star.