NCERT Solutions for Class 8 Science Chapter 17 : Stars and the Solar System

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:

(c) Constellation A constellation is not a member of the solar system. Constellations are groups of stars that form recognizable shapes.

Question 2: Which of the following is NOT a planet of the sun?

(a) Sirius

(b) Mercury

(c) Saturn

(d) Earth

Answer:

(a) Sirius is a star and not a planet of the sun.

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) Phases of the moon occur because we can see only that part of the moon which reflects light towards us. Moon does not produce its own light. We are able to see the moon because the sunlight falling on it gets reflected towards us.

Thus, we see only that part of the moon from which the light of the sun gets reflected 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 a___.

(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 a satellite.

(e) Shooting stars are actually not stars. (Shooting stars are not stars, they are meteors)

(f) Asteroids are found between the orbits of Mars and Jupiter. (Asteroids occupy a large gap between the orbits of Mars and Jupiter)

Question 5: Mark the following statement 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 Stars are not a member of the solar system. The sun and the celestial bodies revolving around it form the solar system.

(b) True Mercury is the smallest planet of the solar system.

(c) False Neptune is the farthest planet in the solar system.

(d) True INSAT is an artificial satellite.

(e) False There are eight planets in the solar system. They are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

(f) False Constellation Orion can be seen during winters around late evenings. It is one of the most magnificent constellations in the sky, visible to the naked eyes.

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

Answer:

Answer:

Venus appears in the western sky after sunset and is called the evening star.

Answer:

The largest planet of the solar system is Jupiter.

Answer:

A constellation is a group of stars that form a recognizable pattern in the sky. The two well known constellations are Ursa Major and Orion.

Answer:

(a) Ursa Major appears like a big dipper. There are three bright stars in the handle and four stars in the bowl of the dipper (as shown in the given figure).

(b) Orion appears like a hunter. Three bright stars appear in the belt, while five bright stars are arranged in the form of a quadrilateral (as shown in the given figure).

Answer:

(i) 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.

(ii) Meteors are small celestial objects that are seen as bright streaks of light in the sky. They burnt out on entering the Earth’s atmosphere because of the heat produced by friction. This results in bright streaks in the sky. They are not planets.

Answer:

In order to locate the Pole star in the sky, first of all Ursa Major or Big Dipper constellation must be located. The bowl of the Big Dipper consists of four bright stars (as shown in the given figure).

Consider two stars at the end of this bowl. Now, draw an imaginary straight line towards the Northern direction connecting these two stars (as shown in the given figure).

This imaginary line meets a star called the Pole Star. The length of the imaginary line from the bowl is about five times the distance between the two stars of the bowl.

Answer:

No. The Earth rotates from West to East on its axis. Hence, all stars in the sky (except the Pole star) appear to move from East to West. With reference to the Earth, the Pole star does not appear to move in the sky because it is located above the axis of rotation of the Earth in the north direction. It appears to remain stationary at a point in the sky.

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 kilometer (km). 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 to 9.46 × 1012 km. A star is located eight light years away from the Earth.

This means that the distance between the star and the Earth is equivalent to the distance travelled by light in eight years, i.e., a star is located 8 × (9.46 × 1012) = 7.6 × 1013 km away from the Earth.

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.

Hence, this ratio suggests that Jupiter can accommodate 1331 number of Earths within it

Question 16: Boojho made the following sketch (Fig. 17.29) 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’s 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.