Lakhmir Singh & Manjit Kaur: Stars and the Solar System- 2 | Lakhmir Singh & Manjit Kaur Solutions: Class 8 Science PDF Download

Q.36. Which celestial objects are also called minor planets?

Asteroids are the celestial objects which are also called minor planets. Asteroids can only be seen through large telescopes.

Q.37. Name one natural and one artificial satellite of the Earth.

Moon is the natural satellite of the Earth. Aryabhatta was the first Indian artificial satellite of the Earth.

Q.38. Name the agency responsible for the development of space science programs in India.

ISRO also known as Indian Space Research Organisation is the agency responsible for the development of space science programs in India.

Q.39. Name the first artificial satellite launched by India.

Aryabhatta was the first artificial satellite launched by India.

Q.40. Name the technique of collecting information about the Earth from an orbiting satellite.

Artificial satellites are used for forecasting weather, transmitting television and radio signals. They are also used for telecommunication and remote sensing.

Q.41. Write the full name of INSAT.

INSAT stands for the Indian National Satellite System. It is a series of multipurpose geostationary satellites launched by ISRO to satisfy the telecommunications, broadcasting, meteorology, and search and rescue operations.

Q.42. Write the full name of IRS.

IRS stands for Indian Remote Sensing satellite program.

Q.43. Name two constellations which are visible in the sky:
(a) in the summer season.
(b) in the winter season.

(a) Ursa Major can be seen during summer time in the early part of the night. It has seven prominent stars.
(b) Cassiopeia is another prominent constellation in the northern sky. It is visible during winter in the early part of the night. It looks like a distorted letter W or M.

Q.44. State whether the following statements are true or false:
(a) Constellation Orion can be seen only with a telescope.
(b) Pole Star is a member of the Solar System.
(c) Mercury is the smallest planet of the Solar System.
(d) Uranus is the farthest planet in the Solar System.
(e) There are nine planets in the Solar System.
(f) Comets are members of the Solar System.
(g) INSAT is an artificial satellite.

(a) This statement is False.
Orion is clearly visible in the night sky from November to February.
(b) This statement is False.
Pole star is a name of Polaris in the constellation Ursa Minor, after its property of being the naked-eye star closest to the Earth’s celestial north pole.
(c) This statement is True.
Mercury is the planet nearest to the Sun. It is the smallest planet of our Solar System.
(d) This statement is False.
Neptune is the farthest planet in the Solar System.
(e) This statement is False.
There are eight planets in the Solar System. In 2006, the International Astronomical Union (IAU) adopted a new definition of a planet. Pluto does not fit this definition. It is no longer a planet of the solar system.
(f) This statement is True.
Comets are the members of the Solar System. They revolve around the Sun in highly elliptical orbits.
(g) This statement is True.
Artificial satellites are man-made. They are launched from the Earth.

Q.45. Fill in the following blanks with suitable words:
(a) The stars appear to ________ in the sky.
(b) The Sun is a ________ whereas Orion is a ________ 
(c) The group of stars that appears to form a recognizable pattern in the sky is known as ________ 
(d) The brightest star in the night sky is ________ 
(e) Ursa Major constellation appears to revolve around the ________ star in the night sky.
(f) Orion constellation can be used to locate the position of ________ star whereas Ursa Major constellation can be used to locate the  ________ star in the night sky.
(g) The planet which is farthest from the Sun is ________ 
(h) The planet which appears reddish in colour is ________ 
(i) The small heavenly bodies revolving around the Sun between the orbits of Mars and Jupiter are called ________ 
(j) Asteroids are found between the orbits of ________ and ________ 
(k) Shooting stars are actually not ________ 
(l) A celestial body that revolves around a planet is known as ________ 
(m) A meteoroid becomes a ________ on entering Earth’s atmosphere.
(n) The long-distance transmission of television programmes has been made possible with the help of ________ satellites.

(a) twinkle.
Stars twinkle because we are able to see them through the thick layers of turbulent atmosphere.
(b) Star and constellation.
The constellation Orion is visible during winter in the late evenings. It also has seven or eight bright stars.
(c) Constellation.
The stars forming a group that has a recognisable shape is called a constellation. We can easily identify them in the night sky.
(d) Sirius.
Sirius is a star system and the brightest star in the Earth’s night sky.
(e) Pole.
Ursa Major can be seen during summer time in the early part of the night. It has seven prominent stars.
(f) Sirius and Pole.
Orion is clearly visible in the night sky from November to February. The pole star is the star which remains fixed at the same place in the sky in the North.
(g) Neptune.
Neptune is the farthest planet from the Sun. It is the fourth largest planet in the Solar System.
(h) Mars.
Mars appears slightly reddish in colour and is also called the red planet. It has two small natural satellites.
(i) Asteroids.
Asteroids are the celestial objects which are also called minor planets. Asteroids can only be seen through large telescopes.
(j) Mars and Jupiter.
Asteroids are the celestial objects which are also called minor planets. Asteroids can only be seen through large telescopes.
(k) Stars.
Meteors are commonly known as shooting stars, although they are not stars. A meteor is usually a small object that occasionally enters the earth’s atmosphere.
(l) Satellite.
A body revolving around another body is called a satellite. Moon is the natural satellite of the Earth. Some planets also have natural satellites.
(m) Meteor.
Meteors are commonly known as shooting stars, although they are not stars. A meteor is usually a small object that occasionally enters the earth’s atmosphere.
(n) Artificial.
Artificial satellites are man-made. They are launched from the Earth.

Q.46. What is meant by ‘celestial objects’? Name any three celestial objects.

The stars, the planets, the moon and many other objects in the sky are called celestial objects. The moon is the brightest object in the night sky. Stars are celestial bodies that emit light of their own. Our sun is also a star. Moon is the natural satellite of the Earth. The Sun and the celestial bodies which revolve around it form the solar system. These celestial bodies include the planets, comets, asteroids and meteors.

Q.47. What is a star? Name the star nearest to the Earth.

Stars are celestial bodies that emit light of their own. Our sun is also a star. It is convenient to express distances of stars in light years. Stars appear to move from east to west. The pole star appears to be stationary from the Earth, because it is situated close to the direction of the axis of rotation of the Earth. Some groups of stars appear to form recognizable groups known as constellation. The Sun is the star nearest to the Earth. It is the source of almost all energy on the Earth. The Sun is the main source of heat and light for all the planets.

Q.48. Why does Pole Star appear to be stationary in the sky?

The pole star appears to be stationary from the Earth, because it is situated close to the direction of the axis of rotation of the Earth. The Pole Star is not visible from the southern hemisphere. Some of the northern constellations like Ursa Major may also not be visible from some points in the southern hemisphere.

Q.49. Do all the stars in the sky move? Explain.

The stars appear to move in the sky. It appears because of the motion of the Earth. Earth is spinning around its own axis and also moves around the Sun. As a result, the stars also appear to move from east to west. A star which rises in the east in the evening, sets in the west in the early morning. All the stars do not appear to move. For example, pole star does not appear to move because it is situated in the direction of earth’s axis.

Q.50. What is a constellation? Name any two constellations.

The stars forming a group that has a recognisable shape is called a constellation. We can easily identify them in the night sky. Ursa Major and Orion are the examples of the constellations. Ursa Major is the constellation which reminds us of a large ladle or a question mark in the night sky. It is also known as the Big Dipper, the Great Bear or the Saptarshi. There are seven prominent stars in this constellation. It appears like a big ladle or a question mark. The constellation Orion is visible during winter in the late evenings. It also has seven or eight bright stars. It is also called the Hunter. The three middle stars represent the belt of the hunter. The four bright stars appear to be arranged in the form of a quadrilateral.

Q.51.
(A) How much time does light take to reach us from the Sun?

Sunlight travels at the speed of light. Light emitted from the surface of the Sun has to travel across the vacuum of space to reach our eyes. It takes an average of 8 minutes and 20 seconds for the sunlight to travel from the Sun to the Earth.

(B) How much time does light take to reach us from the next nearest star ‘Proxima Centauri’?

The next nearest star to Earth is ‘Proxima Centauri’. It is 4.24 light years from the Sun. Its light will take 4.24 years to reach us.

Q.52. What is Solar System? Name the different types of celestial objects which are members of the Solar System.

The Sun and the celestial bodies which revolve around it form the Solar System. It consists of large number of bodies such as planets, comets, asteroids and meteors. The Gravitational force keeps the members of the Solar System bound to the Sun. The Sun is the star having a system of planets with one planet called Earth with life on it. Comets are the member of the Solar System which appears in the sky like a bright ball of light with a long glowing tail. Asteroids are the celestial objects which are also called minor planets. Asteroids can only be seen through large telescopes. Meteors are commonly known as shooting stars, although they are not stars. A meteor is usually a small object that occasionally enters the earth’s atmosphere.

Q.53. What are planets? How many planets are there in the Solar System?

Planets are the members of the Solar System. They look like stars but they do not have light of their own. They reflect the sunlight that fall on them. They keep changing their positions with respect to the stars. A planet revolves around the Sun in a definite path. This path is called an orbit. The time taken by a planet to complete one revolution is called its period of revolution. As the distance of the planet increases from the Sun, the period of revolution increases. A planet also rotates on its axis besides revolving around the Sun. The time taken by the planet to complete one rotation is called its period of rotation. Some planets have moons or satellites revolving around them.

Q.54. Name all the planets of the Solar System in the order of their increasing distances from the Sun.

The Sun and the celestial bodies which revolve around it form the Solar System. The Gravitational force keeps the members of the Solar System bound to the Sun. The Earth is a planet. It is the member of the Solar system. The eight planets in their order of their increasing distance from the Sun are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

Q.55. What are inner planets and outer planets? Name them.

There are eight planets in the Solar System. The first four planets, Mercury, Venus, Earth and Mars are much nearer the Sun than the other four planets. They are called the inner planets. The inner planets have very few moons. The planets outside the orbit of Mars, namely Jupiter, Saturn, Uranus and Neptune are much farther off than the inner planets. They are called the outer planets. They have a ring system around them. The outer planets have large number of moons. The outer planets can be seen only with the help of large telescopes.

Q.56. Why is it difficult to observe the planet Mercury?

Mercury is the nearest planet to the Sun. It is the smallest planet of our Solar System. It is very close to the Sun which makes it very difficult to observe. This is because most of the time it hidden in the glare of the Sun. However, it can be observed just before sunrise or just after sunset, near the horizon. Mercury has no satellite of its own.

Q.57. State one way in which the planets can be distinguished from the stars in the night sky.

Planets are the members of the Solar System. They look like stars but they do not have light of their own. They reflect the sunlight that fall on them. Whereas the stars emit light of their own. The Sun is also a star.

Q.58. What are the various environmental conditions available on Earth which are responsible for the existence and continuation of life on Earth?

Earth is the only planet of the Solar System having life on it. The special environment conditions are responsible for the existence and the continuation of life on the Earth. These conditions include the right distance from the Sun, so it has the right temperature, the presence of water, suitable atmosphere and a blanket of ozone.

Q.59. State one important consequence of each of the following:
(a) Rotation of Earth on its axis.
(b) Motion of tilted Earth around the Sun.

(a) The Earth rotates on its axis taking approximately 24 hours to complete one rotation. Rotation of Earth causes the day night cycle which also creates a corresponding cycle of temperature and humidity.
(b) The plane in which the Earth revolves round the Sun is called the orbital plane of the Earth. The axis of rotation of the Earth is not perpendicular to the plane of its orbit. These two planes are inclined to each other at an angle of 23.5° This tilt is responsible for the change of seasons on the Earth.

Q.60. What is a satellite? Name the natural satellite of the Earth.

Any celestial body revolving around another celestial body is called its satellite. The Earth is the satellite of the Sun because it revolves around the Sun. The bodies revolving around the planets are considered as satellites of the planet. Moon is the natural satellite of Earth.

Q.61. Moon does not have light of its own. How are we able to see the Moon?

Moon is the natural satellite of Earth. It revolves around the Earth. The moon completes one rotation on its axis as it completes one revolution around the Earth. The moon does not produce its own light. We are able to see the moon because the sunlight falling on it gets reflected towards us. Therefore, we are able to see only that part of moon, from which the light of the Sun is reflected towards us.

Q.62. Name the constellation which appears to have the shape of:
(a) a big bear
(b) a distorted W or M
(c) a hunter
(d) a big lion

(a) Ursa Major constellation is also known as the Big Dipper, the Great Bear or the Saptarshi. There are seven prominent stars in this constellation. It appears like a big ladle or a question mark.
(b) Cassiopeia is another prominent constellation in the northern sky. It is visible during winter in the early part of the night. It looks like a distorted letter W or M.
(c) The constellation Orion is has seven or eight bright stars. It is also called the Hunter. The three middle stars represent the belt of the hunter. The four bright stars appear to be arranged in the form of a quadrilateral.
(d) Leo Major appears to have the shape of a big lion. It is visible in the northern hemisphere around the spring. It is easily identifiable through may. Its brightest star is Regulus. Its most prominent pattern of stars is a backwards question mark called the Sickle.

Q.63. What are asteroids? Where are they located?

There is a large gap between the orbits of Mars and Jupiter. This gap is occupied by a large number of small objects that revolve around the Sun. These are called asteroids. Asteroids are the celestial objects which are also called minor planets. Asteroids can only be seen through large telescopes.

Q.64. State two differences between the artificial satellites of the Earth and its natural satellite Moon.

Natural satellites are formed by nature. Moon is the natural satellite of the Earth. Following are the differences between the Moon and the artificial satellites of the Earth:

Q.65. What is an artificial satellite? Name any two artificial satellites launched by our country.

Artificial satellites are manmade and are launched from the Earth. They revolve around the Earth much closer than earth’s natural satellite, the moon. They have many practical applications. They are used for forecasting weather, transmitting television and radio signals. They are also used for telecommunication and remote sensing. INSAT, IRS, Kalpana-1, EDUSAT are artificial satellites.

Q.66. State five uses of artificial satellites.

Artificial satellites are manmade and are launched from the Earth. They revolve around the Earth much closer than earth’s natural satellite, the moon. They have many practical applications. Following are the uses of artificial satellites:

• They are used for forecasting weather.
• They are used for transmitting television and radio signals.
• They are also used for telecommunication and remote sensing.
• They help in scientific research.
• They are used in Global positioning system (GPS).

Q.67. Define light year. How many kilometres make 1 light year?

Light year is the unit used to express distance between the various celestial bodies. Light year is the distance travelled by light in one year. The speed of light is 300,000 km per second. For example, the Sun is nearly 150,000,000 Km i.e. 150 million Km away from the Earth. The distance of the Sun from the Earth may be said to be about 8 light minutes. 1 light year = 9.46 × 1012 Km.

Q.68. What is a comet? Name the comet which was last seen in 1986 after a period of 76 years.

Comets are the member of the Solar System which appears in the sky like a bright ball of light with a long glowing tail. The length of the tail grows in size as it approaches the sun. The tail of a comet is always directed away from the sun. They revolve around the Sun in highly elliptical orbits. The period of revolution of comets around the Sun is usually very long. Many comets are known to appear periodically. Halley’s comet appears after nearly every 76 years. It was last seen in 1986.

Q.69. When does a comet become visible to us?

Comets are the member of the Solar System. They revolve around the Sun in highly elliptical orbits. The period of revolution of comets around the Sun is usually very long. Comets appear periodically. Comets are visible to us in the sky like a bright ball of light with a long glowing tail. The length of the tail grows in size as it approaches the sun. The tail of a comet is always directed away from the sun.

Q.70. What happens to the tail of a comet when it moves far away from the Sun?

Comets are the member of the Solar System. They revolve around the Sun in highly elliptical orbits. Comets appear periodically. Comets are visible to us in the sky like a bright ball of light with a long glowing tail. The length of the tail grows in size as it approaches the sun. The tail of a comet is always directed away from the sun.