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2nd Proof, , Chapter 17 : Stars and the Solar System, , 17, , Stars and the Solar System, Introduction, , 1., , The star-like objects which do not appear to twinkle in the night sky are planets., , 2., , The stars are the brightest object in the night sky. (  or ), , 3., , What are called celestial objects?, , A., , The stars, the planets, the moon and many other objects in the sky are called celestial objects., , 4., , The study of celestial objects and associated phenomena is called astronomy., , (), , The Moon, 5., , The shape of the moon appears to change daily. ( or ), , 6., , Explain the full moon day and new moon day., , A., , The day on which the full disc of the moon is visible is known as full moon day. Thereafter, every, , (), , night the size of the bright part of the moon appears to become thinner and thinner. On the, fifteenth day the moon is not visible. This day is known as New moon day., 7., , The various shapes of the bright part of the moon as seen during a month are called phases of, the moon., , 8., , Explain phases of the moon in detail., , A., , The various shapes of the bright part of the moon as seen during a month are called phases of the, moon. The day on which the full disc of the moon is visible is known as full moon day. Thereafter,, every night the size of the bright part of the moon appears to become thinner and thinner. On the, fifteenth day the moon is not visible. This day is known as new moon day. The next day only a small, portion of the moon appears in the sky. This is known as the crescent moon. Then again the moon, grows larger every day. On the fifteenth day once again we get a full view of the moon., , 9., , Phases of the moon occur because ________________. ***, , (A), , (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., 10., , Moon has its own light. ( or ), , 11., , Though the moon does not produce its own light, we can see it. Give reason., , (), , A., , Moon does not produce its own light but the sunlight falling on it gets reflected towards the earth., , 84, , I am ‘Confident’... I am a Change Maker.

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2nd Proof, , Standard, , : 8 | Science, , Moon is visible to us due to this sunlight which is reflected back to us., 12., A., , Why does the moon change its shape every day?, The Moon doesn’t emit (give off) light itself, the ‘moonlight’ we see is actually the Sun’s light reflected, off the lunar surface. So, as the Moon orbits the Earth, the Sun lights up different parts of it, making, it seem as if the Moon is changing shape., , 13., , The size of the illuminated part of the moon visible from the earth increases every day after the, New moon day., , 14., , Before the full moon day, the sunlit part of the moon visible from the Earth decreases in size every, day. ( or ), , 15., A., , ( ), , We can always see one side of the moon. Give reason., The moon completes one rotation on its axis as it completes one revolution around the Earth. Thus, the side of the moon which is facing the earth remains always towards the earth and we can always, see only one side of the moon., , 16., , The moon completes one revolution around the earth in the same time which it takes to complete, one rotation on its axis., , 17., , The moon’s surface is dusty and barren. ( or ), , 18., , The moon has no atmosphere and has no water., , 19., , Can we hear any sound on the moon?, , A., , (), , No, we cannot hear any sound on the moon’s surface because sound requires medium for, transmission. But the moon has no atmosphere and thus sound can not reach our ears., , 20., A., 21., , Who was the first person to step on the moon?, The American astronaut Neil Armstrong landed on the moon for the first time, on July 21, 1969., The other astronaut who went to the moon with Neil Armstrong was _______., (A) Rakesh Sharma, , (B) Edwin Aldrin, , (C) Kalpana Chawla, , (B), , (D) None of these, , The Stars, 22., , The sun is a star. ( or ), , 23., , Why do the stars appear to us like points?, , A., 24., A., , (), , The stars are millions of times far away from the sun, so the stars appear to us like points., What is a light year?, The distance travelled by the light in one year is called a light year., , 25., , The speed of light is about 300,000 km per second., , 26., , The distance of the sun from the earth is _______, (A) 8 light year, , (B) 8 light minutes, , (B), (C) 4.3 light years, , I am ‘Confident’... I am a Change Maker., , (D) 4.3 light minutes, 85

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2nd Proof, , Chapter 17 : Stars and the Solar System, 27., , 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?***, , A., , The distance between any two stars is generally so big that it can’t be read in kilometres conveniently., Thus, such large distances are expressed in another unit known as the light year., A star is 8 light years away from the earth means that the distance between the star and the earth is, equal to the distance covered by the light in eight years or we can say that the light from that star, takes eight years to reach the earth., , 28., A., , Why are the stars visible only at night?, The stars are present in the sky during the day-time also. However, they are not visible then because, of the bright sunlight., , 29., A., , Why do we see the sun and the other stars rising in the east and setting in the west?, The sun and the other stars remain stationary but the earth rotates on its orbit from west to east, and hence the stars appear to be moving in the direction opposite to the motion of the earth. This is, the reason due to which the sun and the stars appear to rise in the east and set in the west., , 30., A., , Do all the stars in the sky move? Explain. ***, No, the stars in the sky don’t really move. But due to the revolution of the earth they seem to be, moving from the east to west direction. The stars which appear to be rising in the evening in the, east direction set down in the west direction in the early morning., The pole star which is situated in the north direction of the earth’s axis does not appear to move., , 31., , The Pole star is always seen in the North direction., , 32., , Give reason: The Pole star does not appear to move at all and is always seen in the North, direction., , A., , The Pole star lies close to the axis of rotation of the earth, thus it does not appear to move at all and, is always seen in the North direction., Constellations, , 33., , A group of stars that appear to form a pattern in the sky is known as a constellation. ***, , 34., , What is a constellation? Name any two constellations.***, , A., , The group of stars that forms a recognizable pattern in the sky is known as a constellation., Two constellations are; Ursa Major and Orion, , 35., A., 36., , The Ursa Major (Saptarshi) constellation can be seen during which season?, Ursa Major constellation can be seen during summer time in the early part of the night., Ursa Major is also known as _____________., (A) Big Dipper, , 86, , (B) the Great Bear, , (D), (C) the Saptarshi, , I am ‘Confident’... I am a Change Maker., , (D) All of these

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2nd Proof, , Standard, , : 8 | Science, , 37., , The Ursa Major constellation appears like a big ladle or a question mark. ( or ), , 38., , All the stars appear to revolve around the Pole star., , 39., , The pole star is not visible from the southern hemisphere. ( or ), , (), , 40., , Ursa Major may not be visible from some points in the ___________., , (B), , 41., A., , (A) Northern Hemisphere, , (B) Southern Hemisphere, , (C) Poles, , (D) None of these, , (), , Explain how you can locate the Pole Star with the help of Ursa Major.***, For locating the pole stars in the sky, first the big dipper or the Ursa Major constellation must be, found . The bowl of the big dipper consists of the four bright stars., , Imagine the two stars at the end of this bowl. Then make an imaginary straight line towards the, northern direction connecting these two stars., , This imaginary line meets the 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., 42., , The Orion constellation can be seen in the late evenings in the winter season., , 43., , The Orion constellation contains 10 bright stars. ( or ), , (), , 44., , Orion is also called the _____________., , (C), , (A) Ursa Major, 45., A., 46., , (B) Deer, , (C) Hunter, , (D) Magha, , Name the brightest star in the sky., Sirius, Constellation Orion can be seen only with a telescope. ( or )***, I am ‘Confident’... I am a Change Maker., , (), 87

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2nd Proof, , Chapter 17 : Stars and the Solar System, 47., , Draw sketches to show the relative positions of prominent stars in, (a) Ursa Major and (b) Orion, , A., , (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., , 48., A., , Describe the constellation ‘Cassiopeia’., Cassiopeia is a 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, , 49., , Differentiate between the constellations Ursa Major and Cassiopeia., Ursa Major Constellation, , Cassiopeia Constellation, , (1) The number of stars in the Ursa Major, constellation is 7., , (1) The number of stars in the constellation, Cassiopeia is 5., , (2) The constellation Ursa Major is shaped, like a large spoon or a question mark., (3) It is visible during summer time., , (2) The shape of the Cassiopeia constellation is, similar to the distorted letter ‘M’ or ‘W’., (3) It is visible during winter time., , The Solar System, 50., , The Sun and the celestial bodies which revolve around it form the solar system., , 51., , Name two objects other than planets which are members of the solar system.***, , A., 52., , 88, , Comets and asteroids., Which of the following is NOT a member of the solar system?***, (A) An asteroid, , (B) A satellite, , (C) A constellation, , (D) A comet, I am ‘Confident’... I am a Change Maker., , (C)

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2nd Proof, , Standard, 53., A., , : 8 | Science, , Give reason: The objects like planets, comets, etc. keep revolving around the sun., The gravitational attraction between the Sun and the celestial objects like planets, comets, etc. keeps, them revolving around it., , 54., , There are nine planets in the solar system. ( or ) ***, , 55., , Write the names of the planets of the solar system in their order of distance from the, , (), , sun. Which of these planets can be seen with the naked eye?, A., , Planets of the solar system are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune., Out of which Mercury, Venus, Mars, Jupiter and Saturn can be seen with the naked eye. While, Uranus and Neptune cannot be seen with the naked eye., , 56., , Which of the following is not a planet of the sun? ***, (A) Sirius, , 57., , (B) Mercury, , (A), (C) Saturn, , (D) Earth, , According to the new definition of a planet adopted by IAU (International Astronomical Union),, Pluto is no longer a planet of the solar system ., , 58., , The sun is the nearest star from us., , 59., , The sun constantly emits huge amounts of heat and light., , 60., , The moon is the main source of heat and light for all the planets.( or ), , 61., , The planets keep changing their positions with respect to the stars., , 62., , Differentiate between the stars and planets., Stars, (1) The stars have light of their own., , (), , Planets, (1) The planets do not have light of their own., They reflect the sunlight that falls on them., , (2) The stars appear twinkling., , (2) The planets appear statically illuminated., , (3) They do not change their positions., , (3) The planets keep changing their positions, with respect to the stars., , 63., A., 64., , What is an orbit?, A definite path in which a planet revolves around the sun is called an orbit., The time taken by a planet to complete one revolution around the sun is called its period of, revolution., , 65., , The period of revolution decreases as the distance of the planet from the sun increases. ( or ) (), , 66., , Give a reason: The planets do not collide while orbiting the sun., , A., , Every planet is at a different distance from the Sun and has a fixed orbit in which it revolves around, the Sun. The Sun’s gravitational force holds the planets in this place and they do not collide with, each other as their orbits are non-intersecting., I am ‘Confident’... I am a Change Maker., , 89

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2nd Proof, , Chapter 17 : Stars and the Solar System, 67., , The planets revolve around the sun as well as on their own axis. ( or ), , 68., , What do you mean by the period of rotation of a planet?, , A., 69., A., , (), , The time taken by a planet to complete one rotation is called its period of rotation., Define satellite., Any celestial body revolving around another celestial body is called its satellite., , 70., , A celestial body that revolves around a planet is known as a satellite. ***, , 71., , The moon is a satellite of the earth., , 72., , What are artificial satellites?, , A., 73., , Man-made satellites revolving around the earth are called artificial satellites., _____is the nearest planet to the Sun., (A) Mercury, , (B) Mars, , (A), (C) Earth, , 74., , Mercury is the smallest planet of the solar system. ( or )***, , 75., , Write five sentences about the planet Mercury., , A., , (D) Jupiter, (), , (1) It is the closest planet to the Sun in the Solar System., (2) It is the smallest planet of the solar system., (3) It is very difficult to observe it, as most of the time it is hidden in the glare of the sun., (4) It can be observed just before sunrise or just after sunset, near the horizon., (5) It does not have a satellite of its own., , 76., , Mercury has five satellites. ( or ), , 77., , Venus is the closest planet to the earth., , 78., , The brightest looking planet in the solar system is __________., (A) Mercury, , 79., A., , (B) Venus, , (), , (C) Mars, , (B), (D) Jupiter, , In which part of the sky can you find Venus if it is visible as an evening star?***, The planet Venus is found in the western part of the sky after sunset and is said to be known as an, evening star., , 80., A., , In which direction does Venus rotate?, Venus rotates from east to west., , 81., , On Venus, the Sun rises in the west and sets in the east., , 82., , __________ is the only planet in the Solar System on which life is known to exist., (A) Mars, , 83., A., , (B) Earth, , (C) Venus, , (B), , (D) Mercury, , Why is life possible on Earth?, Some special environmental conditions are responsible for the existence and continuation of life on, the Earth. These include just the right distance from the Sun, so that it has the right temperature, range, the presence of water and suitable atmosphere and a blanket of ozone., , 90, , I am ‘Confident’... I am a Change Maker.

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2nd Proof, , Standard, 84., A., , : 8 | Science, , Why does the earth appear blue-green from space?, From space, the earth appears blue-green due to the reflection of light from water and landmass, on its surface., , 85., , The axis of rotation of the earth is perpendicular to the plane of its orbit. ( or ), , (), , 86., , What is responsible for the change of seasons on the Earth?, , (C), , (A) Rotation of earth, , (B) Revolution of earth, , (C) The tilt of its axis, , (D) None of these, , 87., , Mars is the first planet outside the orbit of the earth., , 88., , The planet which appears reddish in colour is Mars. ***, , 89., , How many natural satellites does Mars have?, (A) 4, , 90., , A., 92., A., , (C) 2, , (D) 0, , Write a few points of difference between Mars and Venus., , A., , 91., , (B) 3, , (C), , Mars, , Venus, , (1) Mars is a red planet., , (1) Venus is the brightest planet., , (2) Mars has two satellites., , (2) Venus does not have a single satellite., , (3) It is a planet outside the Earth’s orbit., , (3) Venus lies within the Earth’s orbit., , Name the largest planet of the solar system. ***, Jupiter, Write a short note on Jupiter.,  Jupiter is the largest planet of the solar system.,  It is a giant planet having mass many times more than that of the earth.,  It rotates very rapidly on its axis.,  Jupiter has a large number of satellites. It also has faint rings around it.,  It appears quite bright in the sky.,  Jupiter with its four large moons can be observed with the help of a telescope., , 93., , Saturn appears ____________ in colour., (A) reddish, , (B) yellowish, , (B), (C) bluish, , (D) greenish, , 94., , The beautiful rings around Saturn makes it a unique planet of the solar system., , 95., , Saturn doesn’t have any satellites. ( or ), , (), , 96., , Saturn is the least dense among all the planets. ( or ), , ( ), , 97., , Which of the following planets has less density than water?, , (B), , (A) Venus, 98., , (B) Saturn, , (C) Mars, , Uranus is the farthest planet in the solar system. *** ( or ), I am ‘Confident’... I am a Change Maker., , (D) Mercury, (), 91

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2nd Proof, , Chapter 17 : Stars and the Solar System, 99., A., 100., A., , Name the planets which rotate from east to west?, Venus and Uranus rotate from east to west., What are the inner planets called? Name the inner planets., Mars and the planets within the orbit of Mars are called inner planets. These include the planets, Mercury, Venus, Earth and Mars., , 101., A., 102., A., , Give reason: Uranus, in its orbital motion, appears to roll on its side., Uranus has a highly tilted rotational axis, as a result, in its orbital motion it appears to roll on its side., What are the outer planets? Name them., 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., , 103., , The inner planets have a greater number of satellites as compared to the outer planets., ( or ), , 104., 105., , (), , The arrangement of rings around the outer planets is observed., Differentiate between inner planets and outer planets, , A., , Inner planets, , Outer planets, , (1) The first four planets, Mercury, Venus,, , (1) The planets outside the orbit of Mars, namely, , Earth and Mars are called the inner, , Jupiter, Saturn, Uranus and Neptune are, , planets., , called the outer planets., , (2) There are no ring systems around the, inner planets., , (2) There are ring systems around the outer, planets., , (3) The inner planets do not have a large, , (3) The outer planets have more satellites., , number of satellites., Some Other Members of the Solar System, 106., , Asteroids are found between the orbits of Mars and Jupiter .***, , 107., , What are asteroids?, , A., , There is a large gap in between the orbits of Mars and . This gap is occupied by a large number of, number small objects that revolve around the Sun. These are called asteroids. Asteroids can only be, seen through large telescopes., , 108., , Comets revolve around the sun in highly elliptical orbits., , 109., , A Comet appears generally as a ______________ head with a ______________ tail., (A) bright, long, , 110., 92, , (B) long, bright, , (C) round, short, , The tail of a comet is always directed away from the sun. ( or ), I am ‘Confident’... I am a Change Maker., , (A), , (D) long, bright, ()

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2nd Proof, , Standard, 111., , Halley’s comet appears after nearly every 76 years., , 112., , Shooting stars are actually not stars. ***, , 113., , Write a short note on meteors and meteorites., , A., , : 8 | Science, ,  A meteor is usually a small object that occasionally enters the earth’s atmosphere.,  At that time it has a very high speed. The friction due to the atmosphere heats it up. It glows, , and evaporates quickly. That is why the bright steak lasts for a very short time.,  These are commonly known as shooting stars, although they are not stars.,  Some meteors are large and so they can reach the Earth before they evaporate completely., , The body that reaches the Earth is called a meteorite.,  Meteorites help scientists in investigating the nature of the material from which the solar, , system was formed, 114., , The pole star is a member of the solar system. ( or ) ***, , 115., , What are artificial satellites? Name the satellites launched by India., , A., , (), , Man-made satellites, launched from the earth which revolve around the earth are called artificial, satellites. Satellites launched by India include Aryabhata, INSAT, IRS, KALPANA-1, EDUSAT, etc., , 116., , Man-made satellites that revolve around the earth are called asteroids. ( or ), , 117., , State the uses of artificial satellites., , A., , (), , Artificial satellites have many practical applications. They are used for forecasting weather,, transmitting television and radio signals. They are also used for telecommunication and remote, sensing., , 118., , INSAT is an artificial satellite. ( or )***, , 119., , Match items in column A with one or more items in column B.***, A, , B, , (), , Answer, , (1) Inner planets, , (A) Saturn, , (1) - G, E, , (2) Outer planets, , (B) Pole star, , (2) - A, , (3) Constellation, , (C) Great Bear, , (3) - C, F, , (4) Satellite of the Earth, , (D) Moon, , (4) - D, , (E) Earth, (F) Orion, (G) Mars, , I am ‘Confident’... I am a Change Maker., , 93

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2nd Proof, , Chapter 17 : Stars and the Solar System, (2), , 120., , A, , B, , Answer, , (1) Mercury, , (A) Brightest planet, , (1) - C, , (2) Mars, , (B) Largest planet, , (2) - E, , (3) Venus, , (C) Smallest planet, , (3) - A, , (4) Jupiter, , (D) Lowest density planet, , (4) - B, , (5) Saturn, , (E) Red planet, , (5) - D, , 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 accommodate?***, , A., , Let us consider Earth and Jupiter as two spheres with radii R and R,’ respectively. Given in the question, that the radius of Jupiter is 11 times the radius of the Earth., So, R’= 11R, Volume of sphere of radius r is, given as =, , 4,  r3, 3, ,  Volume of Earth =, , =, , 4,  R3, 3, , And, volume of Jupiter =, , 4, (R’)3, 3, , 4, (11R)3, 3, 4, =1331[ R3], 3, , =, , 121., , The ratio of the volume of Jupiter and Earth, , volume of Jupiter, volume of Earth, , 4,   1331 R3, = 3, 4,   R3, 3, 1331, = 1331 : 1, =, 1, Therefore, this ratio suggests that, Jupiter can fit 1331 number of Earth, in it., , Boojho made the following sketch of the solar system. Is the sketch correct? If not, correct, it.***, , 94, , I am ‘Confident’... I am a Change Maker.

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2nd Proof, , Standard, A., , : 8 | Science, , No, the diagram made by Boojho is not correct, because in the solar system the sequence of the, planets of their distance from the sun is like; Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus,, and Neptune. Here he had changed the positions of the planets Venus, Mars, Neptune and Uranus., Besides this, he had shown in the diagram that the Asteroids belt in the gap between the orbits of, Saturn and Jupiter. This is incorrect. The asteroid belt is located in the middle of the orbits of Jupiter, and Mars. The correct diagram of the solar system is given below:, , ********, , I am ‘Confident’... I am a Change Maker., , 95