NCERT Exemplar Solutions Class 8 Science Stars and the Solar System

Multiple Choice Questions...........................

Question 1:  Morning star is the name given to

(a) pole star

(b) star Sirius

(c) planet Jupiter

(d) planet Venus 

Solution 1: (d) planet, Venus.

Venus shines brighter than any other star and can be seen in the eastern sky before sunrise.

Question 2: Which of the following figures depicts the position of pole star correctly?

Solution 2:

 (a) Since the pole star is located in the north direction of the earth's axis, the response is a).

Question 3:  Sun appears to move from east to west around the earth. This means that earth rotates from

(a) east to west

(b) west to east

(c) north to south

(d) west to north 

Solution 3:  (b) west to east 

The sun appears to rotate around the planet from east to west, indicating that the earth is spinning in the opposite direction.

Question 4:  An astronaut standing on the surface of the moon throws a ball upwards. The ball would

(a) directly fall down from the point it is released.

(b) hang in space.

(c) go up and then come back to the surface of the moon.

(d) keep going up never to come back. 

Solution 4:  (c) go up and then come back to the surface of the moon.

Since the acceleration of gravity on the moon is smaller than on Earth, the ball will rise and then return to the moon's surface.

Question 5: Suppose a new planet is discovered between Uranus and Neptune. Its time period would be

(a) less than that of Neptune.

(b) more than that of Neptune.

(c) equal to that of Neptune or Uranus.

(d) less than that of Uranus. 

Solution 5: (a) less than that of Neptune. 

We already know that the length of time is equal to the distance from the sun. As a result, every new planet discovered between Uranus and Neptune would have a shorter period than Neptune but a longer period than Uranus.

Question 6:  The change in seasons on the earth occurs because

(a) the distance between the earth and the sun is not constant.

(b) the axis of rotation of the earth is parallel to the plane of its orbit.

(c) the axis of rotation of the earth is perpendicular to the plane of its orbit.

(d) the axis of rotation of the earth is tilted with respect to the plane of its orbit.  

Solution 6:  (d) the axis of rotation of the earth is tilted with respect to the plane of its orbit. 

The earth's axis of rotation is not perpendicular to its orbital plane. On Earth, the tilt causes the seasons to shift.

Question 7: The first of a month is the new moon day. On fifteenth of the same month, which of the following figures would represent the phase of the moon?

Solution 7: (a) After 15 days, it will be full moon day, and we will be able to see the full moon as seen in option a).

Very Short Answer Questions...........................

Question 8:  Do stars emit light only during night? 

Solution 8:  Stars emit light all the time, but due to the sun's blinding brightness, we can't see them during the day.

Question 9: Paheli and Boojho observe a bright object in the night sky which was not twinkling. Paheli says, it is a star and Boojho says it is a planet. Who is correct? 

Solution 9:  Boojho is correct since only planets can twinkle, while stars can twinkle while emanating light from a great distance.

Question 10: State whether the following statements are ‘True’ or ‘False’.

(a) The planet nearest to us is Jupiter.

(b) All the stars are at the same distance from us.

(c) The planets do not emit light of their own.

(d) The planets keep changing their position with respect to stars.

(e) The planet Venus appears in the eastern sky before sunrise.

(f) The plane in which the earth revolves around the sun is called the equatorial plane of earth. 

Solution 10:

(a) False - The planets Mars and Venus are the closest to Earth.

(b) False - Different stars are located at different distances from us.

(c) True

(d) True

(e) True

(f) False - In the orbital plane, the Earth orbits around the sun.

Question 11: John saw the full moon on a particular day. After how many days will he be able to see the full moon again? 

Solution 11:  John saw the full moon on a particular day. After approximately 29 days he will be able to see the full moon again.

Question 12:  In the picture of rotating earth given in figure mark the position of the pole star.

Solution 12:

Question 13:  In the given figure out of the positions A, B, C and D which will indicate the position of the sun? Draw the sun at the appropriate position.

Solution 13:

Question 14: In the given figure mark the arrows (←), (→), (↓), or (↑) to show the direction of sunlight.

Solution 14:

Short Answer Questions...........................

Question 15: A star is ten light-years away from the earth. Suppose it brightens up suddenly today. After how much time shall we see this change? 

Solution 15:  After ten years, we will find a difference.

Question 16:  Meteors are not visible during the daytime. Explain the reason.  

Solution 16:   Meteors are not apparent during the day because their visibility is too low in comparison to that of the sun.

Question 17: Why does the moon change its shape daily?

Solution 17:  We just see the part of the moon from which the sun's light is reflected back to us. As a result, the moon's form varies on a regular basis.

Question 18: Paheli saw the moon through a glass window at 8:00 p.m. She marked the position of the moon on the glass pane. She got up at 4 a.m. in the morning. Will the moon be visible at the same position?

 Solution 18:  No, because the moon's location changes during the night.

Long Answer Questions...........................

Question 19: Suppose the moon emits light of its own. Would it still have phases? Justify your answer

 Solution 19: Since the moon does not emit its own light, it merely reflects the sun's. There are phases visible because of reflections of various intensities of light fall on the moon due to the earth's revolution. The moon glows constantly as a result of this, forming stages

Question 20: Figure given below 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?

Solution 20:

At location B, the tail will be the longest.

Question 21:  Explain why we always see the same side of the moon. 

Solution 21:   Since the moon's time of revolution around the planet is equal to the period of rotation of the moon on its axis, we still see the same side of the moon. As a result, we can only see the hand that is facing us.

Look at the given figure 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? 

Solution 22: 

(a) In the evening, we can see the full moon in the eastern sky.

(b) In the evening, we can see the crescent moon in the western sky.

Question 23:  Write the names of all planets in figure.

Solution 23:

Name of the planets are:

1. Mercury
2. Venus
3. Earth
4. Mars
5. Jupiter
6. Saturn
7. Uranus
8. Neptune

Question 24:  Suppose the distance between earth and sun becomes half of its present distance. What is likely to happen to life? 

Solution 24:  Since certain environmental conditions are required for the survival and continuation of life on Earth, life will cease to exist. The right distance between the earth and the Sun is needed for it to have the right temperature range, water, a sufficient atmosphere, and an ozone blanket.

Question 25:  Explain with a diagram of how you can locate pole star with the help of the constellation Great Bear (Ursa Major). 

Solution 25:   Locate Ursa Major's two end stars. Consider the figure below, which depicts a straight line passing through these stars. Extend this imaginary line in the direction of the north. This line will lead to a faintly glowing star. This is a supernova.