NCERT Class 8 Science Chapter 17 - Stars and the Solar System

Chapter 17 - Stars and the Solar System

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
Answer:
b) A satellite

Question 2: Which of the following is NOT a planet of the sun?
a) Sirius
b) Mercury
c) Saturn
d) Earth
Answer:
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.
Answer:
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 _________.
Answer:

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 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. ()
Answer:

a) False
b) True
c) False
d) True
e) False
f) False

Question 6: Match items in column A with one or more items in column B.

Match the following

Answer:

Match the following answer

Question 7: In which part of the sky can you find Venus if it is visible as an evening star?
Answer:
The Venus is found in the western part of the sky after sunset and is said to be known as an evening star.

Question 8: Name the largest planet of the solar system.
Answer:
The largest planet of the solar system is Jupiter. Jupiter's radius is 11 times that of Earth.

Question 9: What is a constellation? Name any two constellations.
Answer:
The stars forming a group that has a recognisable shape is called a constellation. The two constellations are ‘The Big Bear’ and ‘Orion’.

Question 10: Draw sketches to show the relative positions of prominent stars in
a) Ursa Major and b) Orion
Answer:

Question 10 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.

Question 11: Name two objects other than planets which are members of the solar system.
Answer:

• Meteors - Meteors are small celestial objects that are seen as bright streaks of light in the sky. Due to the heat produced by the friction of the Earth’s atmosphere, the Meteors are burnt out while entering in. This causes the bright streaks in the sky. They are not planets.
• Asteroids - The Asteroids are a collection of a huge number of small objects; gases and dust revolving around the sun. Between the orbits of Mars and Jupiter, they occupy the large gap also known as Asteroid Belt. These are not planets.

Question 12: Explain how you can locate the Pole Star with the help of Ursa Major.
Answer:
We can locate the Pole Star with the help of Ursa Major by first looking at the two stars at the end of Ursa Major. Imagine a straight line passing through these stars. Extend this imaginary line towards the north direction. (About five times the distance between the two stars.) This line will lead to a star which is not too bright. This is the Pole star.

Question 13: Do all the stars in the sky move? Explain.
Answer:
No, all the stars in the sky don’t move because the Earth rotates on its axis from west to east. Therefore, all the stars (except the pole star) seem to move from east to west. With reference to Earth, pole star in the sky does not seem to move because it is located above the axis of rotation of the Earth in the north direction. It seems to remain stationary at a point in the sky.

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?
Answer:
The distance of the star from the Earth and the distance between the stars is very large. This makes it difficult to measure in km. So, these huge distances are expressed in light-years. 1 light-year is equal to the distance travelled by the light in one single year. One light-year means 9.46 × 10¹² km. A distance between star and Earth is approximately 8 light-years. This means the distance between them is equal to the distance travelled by the light in 8 years, i.e. distance of the star is 8 × (9.6 × 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 accomodate?
Answer:
Let the radius of Earth be x.
Earth’s volume = 4/3 × π × (x)³
Radius of Jupiter = 11x
Volume of Jupiter = 4/3 × π × (11x)³ = 1331(4/3 × π × x³)
Volume of Jupiter/Volume of Earth = 1331 (4/3 × π × x³)/4÷3 × π × r³ = 1331
Therefore, 1331 Earths, the Jupiter can accommodate.

Question 16: Boojho made the following sketch (Fig. 17.29) of the solar system. Is the sketch correct? If not, correct it.

Fig 17.29

Answer: No, the diagram made by the Boojho is not correct, because in the solar system the sequence of the planets of their distance from the sun is wrong. The correct order will be:

Fig 17.29 Answer

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