NCERT Solutions for Class 8 Science Chapter 17 Stars And The Solar System are provided here with simple step-by-step explanations. These solutions for Stars And The Solar System are extremely popular among class 8 students for Science Stars And The Solar System Solutions come handy for quickly completing your homework and preparing for exams. All questions and answers from the NCERT Book of class 8 Science Chapter 17 are provided here for you for free. You will also love the ad-free experience on Meritnation’s NCERT Solutions. All NCERT Solutions for class 8 Science are prepared by experts and are 100% accurate.
Page No 97:
Question 1:
Morning star is the name given to
(a) pole star (c) planet Jupiter
(b) star Sirius (d) planet Venus
Answer:
Morning star is the nickname given to planet Venus. It is also called the evening star but is not a star. It's a planet.
Hence, the correct answer is option (d).
Page No 97:
Question 2:
Which of the following figures depicts the position of pole star correctly?
Answer:
Pole star is found near the north pole of the earth.
Hence, the correct answer is option (a).
Page No 97:
Question 3:
Sun appears to move from east to west around the earth. This means that earth rotates from
(a) east to west (c) north to south
(b) west to east (d) west to north
Answer:
The earth rotates from west to east because of which the sun rises in the east and sets in the west.
Hence, the correct answer is option (b).
Page No 98:
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.
Answer:
The ball will go up to a certain height and then fall down due to the gravity of the moon.
Hence, the correct answer is option (c).
Page No 98:
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.
Answer:
The time period will be more than uranus and less than neptune. We can figure this out using Kepler's third law which states that the square of time period is directly propotional to the cube of the distance from the sun.
Hence, the correct answer is option (a).
Page No 98:
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.
Answer:
Because the axis of rotation of the earth is tilted with respect to the plane of its orbit, different parts of the earth gets different amount of sun's direct rays which is one of the major cause of seasons.
Hence, the correct answer is option (d).
Page No 98:
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?
Answer:
The fifteenth day of the month will again be the full moon day.
Hence, the correct answer is option (a).
Page No 99:
Question 8:
Do stars emit light only during night?
Answer:
No. They emit light throughout the day, that is, always. But because of the excessive brightness of the sun during the daytime, we are unable to see their light.
Page No 99:
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?
Answer:
Boojho is correct becasue stars always twinkle. But planets or other celestial bodies which do not have their own heat and light do not twinkle since they are very near to us compared to the stars.
Page No 99:
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 equatorial plane of earth.
Answer:
(a) False. Becasue the nearest planet to us is Venus. It is also visible with our naked eyes.
(b)False. The stars are not all at the same distance from us. Some stars are closer and some are farther away. Also, they come in a variety of sizes and brightness.
(c)True. The planets do not have their heat and light. They reflect the light of the sun towards us like the moon.
(d) True. The planets move around the sun, so relative positions keep changing with respect to stars. So the stars appear to be at the fixed position with respect to each other whereas the distance between the planets keep on changing.
(e) True. Venus is the only planet that rotates clockwise, so it appears in the eastern sky in the morning before sunrise.
(f) False. The plane passing through the equator is called the equatorial plane. The plane in which the earth revolves around the sun is called ecliptic plane.
Page No 99:
Question 11:
John saw full moon on a particular day. After how many days will he be able to see the full moon again?
Answer:
The average time between two full moons is 29.53 days. Thus, John will see the full moon again after 29.53 days.
Page No 99:
Question 12:
In the picture of rotating earth given as the given figure mark the position of pole star.
Answer:
Position of polar star is as shown in the diagram.
Page No 100:
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.
Answer:
Sun will be at position C.
Page No 100:
Question 14:
In the given figure mark the arrows (←), (→), (↓), or (↑) to show the direction of sunlight.
Answer:
Page No 101:
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?
Answer:
A 'light year' is a unit of distance which is equal to the distance travelled by light in 1 year. Thus, the star which is ten light years away from the earth, will be visible to us after 10 years.
Page No 101:
Question 16:
Meteors are not visible during the daytime. Explain the reason.
Answer:
Meteors are not visible during the daytime because the brightness of a meteor is extremely small as compared to that of the sun.
Page No 101:
Question 17:
Why does the moon change its shape daily?
Answer:
The moon does not emit light itself, the 'moonlight' we see is actually the Sun's light reflected off the surface of the Moon. So, as the Moon orbits the Earth, the Sun lights up its different parts, due to which it seems as if the moon is changing shape.
Page No 101:
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?
Answer:
No, the moon will not be visible at the same position. As the moon revolves around the earth, its position keeps on changing. Hence, the moon will not be seen at the same position.
Page No 101:
Question 19:
Suppose the moon emits light of its own. Would it still have phases? Justify your answer.
Answer:
No, it will not have the phases. As, the phases are seen because the moon does not emit its own light and reflects the incident light of the sun on its some part. If the moon has its own light, then phases will not be seen anymore.
Page No 101:
Question 20:
In the given figure 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?
Answer:
The tail will be longest at position B as shown in the figure.
Page No 102:
Question 21:
Explain why we always see the same side of moon.
Answer:
The moon rotates around the earth in an orbit, and at the same time it rotates on its own axis too. The time period to complete one rotation around its axis is the same as the time period to complete one revolution around the earth in the orbit. So, the moon always shows the same side to us.
Page No 102:
Question 22:
Look in 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?
Answer:
(a) In eastern part of the sky, we will see the full moon in the evening.
(b) In western part of the sky, we will see the crescent moon in the evening.
Page No 102:
Question 23:
Write the names of all planets in the given figure.
Answer:
Increasing order of distance of planets from the sun is:
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Mercury is the closest while Neptune is the farthest planet from the sun as shown in figure:
Page No 103:
Question 24:
Suppose the distance between earth and sun becomes half of its present distance. What is likely to happen to life?
Answer:
The right distance from the sun maintains the right temperature range, suitable for the presence of water, a suitable atmosphere and a blanket of ozone to exist life on the planet earth. If the distance between earth and sun becomes half of its present distance, life will no longer exist on the planet earth. The harmful ultraviolet rays from the sun may burn species on the earth. The rotation and the acceleration due to gravity will also be affected and hence the environmental synchronization may spoil.
Page No 103:
Question 25:
Explain with a diagram how you can locate pole star with the help of the constellation Great Bear (Ursa Major).
Answer:
First, we have to locate the two end stars of Ursa Major. Then imagine a dotted straight line passing through these stars as shown in the figure. Now, proceed this imaginary line towards the north direction as shown. This extended straight imaginary line will indicate a star which is not too bright. This is the pole star.
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