1 UNIVERSE. I. Tick ( ) the most appropriate answer. 1. Our solar system belongs to:

Transcription

1 1 UNIVERSE I. Tick ( ) the most appropriate answer. 1. Our solar system belongs to: (a) elliptical galaxy (b) spiral galaxy (c) irregular galaxy (d) none of these 2. The name of our galaxy is: (a) andromeda galaxy (b) milky way galaxy (c) whirlpool galaxy (d) none of these 3. Shooting star is a: (a) comet (b) meteor (c) meteorite (d) none of these 4. The planet farthest from the Sun is: (a) Jupiter (b) Uranus (c) Saturn (d) Neptune 5. The planet nearest to the Sun is: (a) Venus (b) Mars (c) Mercury (d) Earth 6. A star like body with a long tail is called: (a) comet (b) meteor (c) pluton (d) none of these 7. The instrument used to observe stars and other heavenly bodies is: (a) periscope (b) microscope (c) telescope (d) endoscope 8. The first satellite put into space by India is: (a) Insat (b) Aryabhatta (c) Rohini (d) Bhaskara 9. The branch of science that studies the heavenly bodies of the universe is called: (a) astrology (b) astronomy (c) biology (d) anatomy 10. Pole Star belongs to the constellation: (a) Ursa Major (b) Ursa Minor (c) Orion (d) Scorpio 11. The planet with rings around itself is: (a) Uranus (b) Jupiter (c) Saturn (d) Pluto 12. The planet farthest from the sun is: (a) Jupiter (b) Neptune (c) Mercury (d) Saturn 13. The star nearest to the earth (other than the sun) is: 1

2 (a) Betelguese (b) Sirius (c) Regel (d) Proxima centauri 14. The streak of light caused by a heavenly body burning completely while moving through the atmosphere is called: (a) a comet (b) a meteor (c) an asteroid (d) a meteorite 15. Our solar system belongs to the : (a) Whirl pool galaxy (b) Seyfert galaxy (c) Milky Way galaxy (d) Radio galaxy 16. The time taken by the light to reach the Earth from the Sun is : (a) 8 minutes and 20 seconds (b) 20 minutes and 8 seconds (c) 6 minutes and 14 seconds (d) 14 minutes and 6 seconds 17. The largest planet of the solar system is: (a) Saturn (b) Uranus (c) Neptune (d) Jupiter 18. Saturn has: (a) 22 moons (b) 39 moons (c) 30 moons (d) 48 moons 19. The coldest planet of the solar system is: (a) Neptune (b) Mercury (c) Venus (d) Mars 20. The diameter of moon is: (a) 3076 km (b) 3476 km (c) 3746 km (d) 3646 km 21. The rock objects that orbit the Sun between the inner and outer planets are: (a) comets (b) meteors (c) asteroids (d) moons 22. Solar eclipse occurs during: (a) full moon (b) new moon (c) first quarter (d) last quarter 23. Ocean tides are caused by the gravitational pull of: (a) the moon (b) the sun (c) both the moon and the sun (d) none of these Ans. 1. (a) 2. (b) 3. (b) 4. (d) 5. (c) 6. (a) 7. (c) 8. (b) 9. (b) 10. (b) 11. (c) 12. (b) 13. (d) 14. (b) 15. (c) 16. (a) 17. (d) 18. (c) 19. (a) 20. (b) 21. (c) 22. (b) 23. (a) II (A). Complete the given sentences with appropriate words. 1. is a vast unimaginable space, which encompasses 2

3 the stars, planets and everything which can be imagined. 2. A vast collection of billions of, along with vast amount of and dust in an isolated place in the universe is called galaxy. 3. Our Sun is a medium star in the galaxy called. 4. The light of the Sun reaches the Earth in minutes and 20 seconds. 5. The Sun is times heavier than Earth. 6. The temperature of the gas particles in the of the Sun can be as high as 1,700,000 C. 7. The middle region of Sun s atmosphere is called. 8. The average temperature of Sun s is 6000 C. 9. The shape of solar system resembles an inverted. 10. The nearest pluton which does not revolve around the Sun in the same plane, as the other planets do is. 11. The time taken by the Moon to complete one revolution around the Earth with reference to Sun is called month. 12. The time taken by the Moon to complete one revolution around the Earth is called month. 13. A group of stars forming a recognisable shape is known as. 14. The is the star nearest to the earth. 15. is the only planet where life exists in our solar system. 16. are the building blocks of the universe. 17. The temperature of the Sun at the centre is C. 18. is the only planet which rotates on its axis from east to west. 19. is a periodic comet. 20. All stars except the star appear to move from east to west. 21. Moon is a celestial body that revolves round the. 22. There are number of constellations known. 3

4 23. The only planet which does not revolve around the Sun in the same plane as the other planets do is. Ans. 1. Universe 2. Stars, hydrogen 3. Milky Way , corona 7. chromosphere 8. photosphere 9. Saucer 10. Pluto 11. synodic 12. sidereal 13. constellation 14. Sun 15. Earth 16. Galaxies million 18. Uranus 19. Halley s comet 20. Pole 21. Earth Uranus II (B). Give an appropriate word for the following. 1. The second closest star to the Earth is. 2. The total number of zodiacal constellations is. 3. The unit used to measure astronomical distances is. 4. The planet that has no atmosphere is. 5. Mars is called the planet. 6. The shape of the milky Way galaxy is. 7. The duration of time between one new Moon day and the next new Moon day is days. 8. The space research programmes of India are managed by. 9. The branch of science which deals about the universe and heavenly bodies is called. 10. The nearest star from the Earth is. 11. Pole star belongs to the constellation. 12. India s first satellite in space was. 13. The nearest planet from the Sun is. 14. The planet farthest from the Sun is. 15. Our solar system belongs to. 16. The streak of light caused by a heavenly body burning completely while moving through the atmosphere is called. 17. The planet with rings around itself is. 18. The time taken by the light to reach the Earth from the Sun is. 4

5 19. The planet which appears reddish in colour is. 20. Shooting stars are called. 21. The very small heavenly bodies revolving round the Sun between the orbits of Mars and Jupiter are called. 22. The temperature of the Sun at the centre is. Ans. 1. Proxima Centauri Light year 4. Mercury 5. Red 6. Spiral 7. 29½ 8. Indian space Research Organisation (ISRO) 9. Astronomy 10. Venus 11. Ursa Minor 12. Aryabhatta 13. Mercury 14. Neptune 15. Milky Way galaxy 16. Shooting Star 17. Saturn min. 20 sec 19. Mars 20. Meteors 21. Asteroids million C III (A). Write true or false for each statement given below. 1. Remote sensing is a technique of collection of information about an object, without a physical contact. 2. The device which receives and then transmits electromagnetic signal in an artificial satellites is called transponder. 3. The remote sensing satellites are placed in geostationary orbit. 4. The distance of geostationary orbit from the Earth is 15,000 km. 5. The temperature of the chromosphere is 1,700,000 C. 6. The plane of the orbits of all the planets around the Sun is same. 7. Planet Jupiter has 60 moons revolving around it. 8. High tides are formed on Full Moon and New Moon days only. 9. Lunar eclipse lasts longer because the Earth forms a very big shadow. 10. A meteorite is a part of meteor, which failed to burn in Earth s atmosphere. 11. Pluto is the smallest planet of the solar system. 12. Comets are the members of the solar system. 13. Moon is a satellite of Earth. 14. Mercury has two satellites. 15. Moon is a luminous heavenly body. 5

6 Ans. 1. True 2. True 3. False 4. False 5. False 6. True 7. False 8. False 9. True 10. True 11. False 12. False 13. True 14. False 15. False III (B). Statements given below are incorrect. Write correct statements. 1. The main cause of tides in ocean is the gravitational pull of Sun and the Jupiter. Ans. The onain cause of the tides is the gravitational pull of the Moon on the Earth. 2. The shadow caused by heavenly bodies on one another is called meteor. Ans. The shadow caused by heavenly bodies on one another is called eclipse. 3. The solar eclipse takes place on New Moon night. Ans. The solar eclipse takes place on New Moon day. 4. The lunar eclipse takes on Full Moon day. Ans. The lunar eclipse takes on Full Moon night. 5. The lunar eclipse does not last longer as compared to solar eclipse. Ans. The solar eclipse does not last longer as compared to lunar eclipse. 6. Pole Star is one of the stars in Ursa Major. Ans. Pole Star is one of the Stars in Ursa Minor. 7. The Halley s comet appears in the sky after 67 years. Ans. The Halley s comet appears in the sky after 76 years. 8. In geostationary orbit, a satellite is at a distance of 53,880 km from the Earth. Ans. In geostationary orbit, a satellite is at a distance of 35,880 km from the Earth. 9. A satellite in a geostationary orbit is used for remote sensing. Ans. A satellite in a geostationary orbit is used for conveying messages like speech, fax etc, i.e. satellite communication. 10. A satellite in Sun-synchronous orbit is used for weather monitoring. Ans. A satellite in Sun-synchronous orbit is used for remote sensing. 11. Kilometre is a convenient unit for measuring distances in the universe. Ans. Light year or parsec is a convenient unit for measuring distances in 6

7 the universe. 12. Earth is the largest planet of the solar system. Ans. Jupiter is the largest planet of the solar system. 13. Mercury is seen in the sky just before sunrise. Ans. Venus is seen in the sky just before sunrise. 14. Orion is a member of the solar family. Ans. Orion is a constellation. It is not a member of the solar family. 15. Moon is a luminous body. Ans. Moon is a non-luminous body. 16. The Sun is a glowing ball of gases, mostly hydrogen and helium. Ans. The Sun is a glowing ball of gases, the chief gas hydrogen. 17. Meteors form craters on the surface of the earth. Ans. Meteorites form craters on the surface of the Earth. 18. Ursa Major is a asteroid. Ans. Ursa Major is a constellation. 19. A comet s tail always points towards the Sun. Ans. A comet s tail always points away from the Sun. IV. Match the following. 1. Shooting star (a) Ursa Major 2. Constellation (b) Milky Way 3. Brightest planet (c) Moon 4. Artificial satellite (d) Halley 5. Galaxy (e) Meteors 6. Periodic comet (f) Sun 7. Natural satellite (g) Venus 8. Star (h) INSAT Ans. 1. (e), 2. (a), 3. (g), 4. (h), 5. (b), 6. (d), 7.(c), 8. (f) V. Differentiate between the following. 1. Star and planet Ans. Star and planet: Stars are heavenly bodies which twinkle in the sky and have their own heat and light while planets are heavenly bodies which do not twinkle and do not have their own heat and light. 7

8 Planets get their light from the stars and move in definite orbits around the stars 2. Planet and satellite Ans. Planet and satellite: Planets are heavenly bodies which revolve around the sun while satellites are heavenly bodies that revolve around the planets. 3. Star and shooting star Ans. Star and shooting star: The heavenly bodies which twinkle and have their own heat and light are called stars. When a meteor enters the Earth s atmosphere, it glows and burns, its path appears as a streak of light in the night sky, it is called shooting star. 4. Meteors and meteorites Ans. Meteors and meteorites: Meteors are heavenly bodies made up of rocks and metals and when enters Earth s atmosphere, glow and burn due to friction of air. Some of the large meteors which do not burn completely on entering the atmosphere of the earth reach the earth s surface. They are called meteorites. 5. Galaxy and constellation Ans. Galaxy and constellation: A large group of stars, dust and low density gases, bound together by their own gravity, is called a galaxy. The stars which appear in the from of closed groups and form recognisable patterns are known as constellations. VI. Give reasons for the following. 1. Sun appears to move from east to west. Ans. Since Earth moves from west to east on its axis, so the Sun appears to move from east to west. 2. Pole Star appears to be stationary. Ans. Pole Star appears to be stationary because the pole Star lies on the axis of rotation of the Earth. The position of pole Star does not change with time when the Earth spins about its axis. 3. Neptune is the coldest planet. Ans. Amongst the planets Neptune is the farthest from the sun, so it is the coldest planet. 8

9 4. Life is possible only on the Earth. Ans. Earth is the only planet which has water and air which are essential for life. So life is possible only on the Earth. 5. Mercury and Venus are called the morning and evening stars. Ans. Mercury and Venus are known as morning and evening stars because they can be seen in the east before sunrise and in the west just after sunset. 6. Meteors become luminous on entering the Earth s atmosphere. Ans. When a meteor enters the Earth s atmosphere, it gets heated due to friction of air. The heat produced is so high that the meteor becomes luminous. 7. Kilometre is not a convenient unit to measure distances in the universe. Ans. The Stars are very far from each other. So kilometre is not a convenient unit to measure distances in the universe. The distance in the universe is measured in terms of light year and parsec. 8. Constellations seem to be moving from east to west. Ans. Since our Earth rotates from west to east on its axis, so constellations seem to be moving from east to west. 9. Not many meteorites hit the Earth s surface. Ans. All meteorites are meteors when in space. Most of them burn to ashes when enters the Earth s atmosphere due to friction of air. So only some meteorites which do not burn completely on entering the Earth s atmosphere hit the Earth s surface. 10. We always see only one face of the Moon. Ans. Moon completes one revolution around the Earth in 27.3 days. It also rotates once on its axis in the same period of time. So, we always see only on face of the Moon. VII. Answer the following questions: 1. (a) Define the following: (i) Galaxy (ii) Universe (b) Approximately how many galaxies are in the universe? (c) Name the galaxy in which our Sun is located. (d) Name the galaxy, which is nearest to our galaxy. 9

10 Ans. (a) (i) Galaxy: The vast collection of billions of stars, along with a vast amount of hydrogen and dust in an isolated place in the universe, is called galaxy. (ii) Universe: The vast unimaginable space, which encompasses most of the distant stars, planets and everything else is called universe. (b) There are about 100 billion galaxies scattered all over the universe. (c) Our sun is located in Milky Way galaxy. (d) The galaxy which is nearest to our galaxy is andromeda galaxy. 2. (a) What is solar system? (b) Name all the planets around the Sun in the order of increasing distance from the Sun. (c) Which is the largest planet? (d) Name the planet on which life exists. (e) Name two planets which do not have Moon around them. Ans. (a) The Sun and eight planets, along with their natural satellites (moon) and the plutons, constitute solar system. (b) The planets in order of increasing distance from the Sun are (i) Mercury (ii) Venus (iii) Earth (iv) Mars (v) Jupiter (vi) Saturn (vii) Uranus (viii) Neptune. (c) Jupiter is the largest planet. (d) Life exists on Earth. (e) Mercury and Venus have no moon. 3. What do you understand by the following terms: (a) Sidereal month of Moon (b) Synodic month of Moon Ans. (a) Sidereal month of Moon: The Moon revolves around the Earth once in about days. This time taken by the Moon to complete one revolution around the Earth is called Sidereal month. (b) Synodic month of Moon. The period from new Moon to new Moon or full Moon to full Moon is about 29½ days. This time taken by the moon to complete one revolution around the Earth 10

11 with reference to Sun, is called Synodic month. 4. Why no life exists on the surface of Moon? Give two reasons. Ans. No life exists on the surface of Moon because: (i) There is no water on Moon (ii) There is no atmosphere on Moon. 5. What do you understand by the term Phases of Moon? Ans. The waxing or waning of the disc of the Moon every night as it revolves around the Earth is called phases of the Moon. 6. (a) What are tides? (b) What is the main cause of high tides? (c) How is high tide formed? (d) Give any two advantages of high tides. Ans. (a) The regular rise or fall of water level of sea, due to gravitational pull of the Moon is called tide. (b) The main cause of tide is gravitational pull of the Moon on the Earth. (c) The mass of sea water is strongly attracted by the Moon due to its gravitational pull. Thus the sea water tends to bulge outwards towards the Moon. At the opposite side sea water will be attracted less. Thus, on the whole, sea water bulges up on the side towards Moon and on opposite side resulting in the rise in level of sea water, which is called high tide. (d) The two advantages of high tides are: (i) High tides help in bringing larger ships to harbour. (ii) High tides help in generating electric current at suitable places. 7. (a) Draw a neat diagram for the formation of lunar eclipse. (b) On which day does lunar eclipse take place, according to lunar calendar? (c) Why does lunar eclipse last longer as compared to solar eclipse? (d) Why is lunar eclipse a fairly common phenomenon as compared to the solar eclipse? 11

12 Ans. (a) (b) According to lunar calendar, lunar eclipse takes place on full Moon night. (c) Lunar eclipse lasts for a long time because the Moon has to pass through a very large shadow of the Earth. (d) During lunar eclipse, the Moon completely disappears in the shadow of the Earth and has to pass through a very large shadow of Earth. So it lasts for a longer time and fairly common as compared to solar eclipse. 8. (a) What do you understand by the term constellation? (b) In which constellation is located pole star? (c) By drawing neat diagrams, show the constellations of (i) Ursa Major (ii) Orion (iii) Cassiopeia. Ans. (a) A group of few stars whose arrangement can be compared to the figure of some animal or any other known thing is called constellation. (b) Pole star belongs to Ursa Minor. (c) 12

13 9. (a) Write a brief note on comets. (b) After how many years does Halley s comet complete one revolution of the Sun? Ans. (a) comets are heavenly bodies which revolve around the Sun in an elliptical path. They appear in the sky like a ball of fire with a long tail. The tail of the comet always points away from the Sun. (b) Halley s comet takes 76 years to complete one revolution of the Sun. 10. Define : (a) Meteors, (b) Meteorites Ans. (a) The pieces of rocks floating in spaces which get heated up on entering into Earth s atmosphere and thus, appear like stars are called meteors. (b) A part of meteor which fails to burn in Earth s atmosphere and hence reaches the surface of Earth is called meteorite. 11. (a) What is an artificial satellite? (b) Name three satellites put into the space by India. Ans. (a) Man made objects orbiting around the Earth in outer space, are called artificial satellites. (b) Some satellites launched by India are Aryabhatta, Bhaskara, Apple, Rohini etc. 12. (a) What do you understand by the term satellite communication? (b) Name and define the orbit in which a communication satellite is placed. (c) How are the messages exchanged through communication satellite? Ans. (a) The process of conveying messages like speech (in telephone), fax (in passing printed matter or pictures), radio and television broadcasts through satellites stationed in outer space in geostationary orbits, is called satellite communication. (b) The orbit in which a communication satellite is placed is called geostationary orbit. By geostationary orbit, we mean that satellite is so positioned in the outer space that to an independent observer on the Earth, it appears stationary. 13

14 (c) The messages are exchanged in communication satellites through transponder. The transponders receive audio and video electromagnetic signals from broadcasting station on the Earth and then transmit them back in all directions towards the Earth. 13. (a) What do you understand by the term remote sensing? (b) Into what kind of orbit are placed remote sensing satellites? (c) Name five kinds of surveys which can be achieved through remote sensing satellites. Ans. (a) The technique of collecting information about an object from a distance without making any physical contact with that object, is called remote sensing. (b) Remote sensing satellites are placed in sun-synchronous orbit. (c) The five kinds of surveys which can be achieved through remote sensing satellites are : (i) Ground water surveys. (ii) Forest cover surveys. (iii) Waste land surveys. (iv) Crop yield surveys. (v) Underground surveys of minerals, coal and petroleum. 14. How are artificial satellites employed for weather forecasting? Ans. Satellites employed for weather forecasting have highly sensitive instruments and cameras. They continuously gather information regarding temperature, pressure, etc, of the earth, these data are continuously relayed to meteorological stations on which generate charts regarding weather. These charts are then analysed by specialists to predict weather at a particular place. 15. Name two units in which large distances in the universe are measured. Ans. (i) light year (ii) parsec 16. What is light year? Ans. The distance traveled by light in one year is called light year. 17. What is relation between a light year and kilometre? Ans. 1 light year = km 18. What is relation between a light year and parsec? Ans. 1 parsec = 3.26 light year 19. Name the two heavenly bodies other than planets, which are the 14

15 members of solar system? Ans. Natural satellites and Sun are the members of solar system. 20. Many stars are much bigger than the Sun. Why do these appear much smaller than the Sun? Ans. Many stars are much bigger than the Sun but appear much smaller than the Sun because they are very far away from us. 21. A star is 5 light year away from the Earth. What does it mean? Ans. 1 light year = km. The above statement means that the star is km i.e., km away from the Earth. 22. (a) What is an eclipse? (b) On which day solar eclipse takes place according to lunar calendar. (c) Draw a neat diagram for the formation of solar eclipse. (d) Why does solar eclipse last for a very small time at a given place? (e) Why solar eclipse does not take place every month? Ans. (a) The shadow cast by the heavenly bodies on each other is called an eclipse. (b) According to lunar calendar, solar eclipse takes place on new Moon day. (c) (d) Solar eclipse lasts for a very small time at a given place because shadow of the Moon is very small and hence the Earth, with revolving round the Sun, easily passes out of this shadow region. (e) Solar eclipse does not take place every month because many a times the shadow of the Moon does not reach the Earth. 23. Answer the following questions regarding our sun: (a) How far is it from the Earth? (b) How many times is it heavier than the Earth? 15

16 (c) What constitutes our sun? (d) What is the temperature of (i) photosphere (ii) core? Ans. (a) The Sun is 150 million kilometres form the Earth. (b) The Sun is approximately 300,000 times heavier than Earth. (c) The Sun is a huge ball of flaming gases. About 70% of the mass of the Sun is made of hydrogen gas, 28% of helium gas and 2% of heavier elements such as carbon, nitrogen, oxygen etc. (d) The temperature of photosphere is 6000 C and core is 15 million C. VIII. Practice for numerical problems: 1. The distance of the star Alpha Centauri from the Earth is 4.3 light years. Calculate the distance in kilometres. Ans. We know that, 1 light year = km 4.3 light years = km = km So, the distance of Alpha Centauri from the Earth is km. 2. A particular star is 10 parsec away from the Earth. Calculate the distance of that star in (a) light years. (b) kilometres. Ans. (a) (b) 1 parsec = 3.26 light year 10 parsec = light year = 32.6 light year. 1 light year = km 32.6 light years = km = km = km The star is 32.6 light years or km away from the earth. 3. Halley s Comet was last seen in In which year will it be seen again on Earth? Ans. Halleys comet will be seen again on Earth after 76 years i.e. in the year