NOTES PREPARED BY
ASHAQ HUSSAIN BHAT
TEACHER SCHOOL
EDUCATION DEPARTMENT
JAMMU AND KASHMIR
CHAPTER 15
Stars And The Solar System
Celestial Objects: Objects in the sky.
Full moon day: Day on which the whole disc of the moon is visible.
Constellation: Starts forming a group that has a re cognizable shape.
Solar system: Consists of planets, comets, asteroids and meteors.
Orbit: The path of planet on which it revolves around the sun.
Asteroids : Large number of small objects in the gap between orbits of Mars & Jupiter that revolve around the Sun.
Comets:Celestial bodies that revolve around the Sun is, highly, elliptical orbits.
Meteors: Shooting stars, bright streak of light in the sky, usually, a small heavenly object moving around the sun.
INTEXT QUESTIONS (Page 190)
Q.1. What are the celestial bodies? Name any three celestial bodies?
Ans:-. The stars, the planets, the moon and many other objects in the sky are called celestial bodies. The carth, moon, planets, sun, stars, meteors, comets etc., are the celestial bodies.
Q.2. Why do you classify the sun as a star?
Ans. The sun dominates the solar systems and accounts for 99.9% of total matter of the whole system. The sun is the source of all the energy in solar system and shine with its own light that's why we classify it as a star.
Q.3. Why do the star appear like point objects?
Ans. The stars appear, like; point objects because they are very far away from the earth
Q.4. What is a constellation? How does the constellation differ from a star.
Ans. Constellations are small group of stars appearing in the space in specific shape. The difference between constellation and star is stars appear to move from east to west but constellations are fixed
Q.5. Name a star which appears stationery from the earth, in which constellation is it situated?
Ans. The pole star appears stationery from the earth. It is situated in Ursa Minor constellation.
Q.6. What is "a light minute"? How many light minutes is the earth from the sun?
Ans. The distance travelled by the light at a speed of 300,000 km/s in one minute is called a light minute.
1 light minute= 300,000 km/s x 1 minute
= 300,000 km/s x 1 minute
= 18,000,000 km = 18x106 km
The sun is at a distance of 1.5x10⁸ km from the earth. The distance of the sun from the earth is 150 million kilometers.
Q.7 How much time is involved from one new moon to another new moon as seen from the surface of the earth?
Aus. Fitteen days time is involved from one new moon to the another new moon as seen from the surface of the earth.
Q.8. In how much time does the moon complete one rotation about its axis?
Ans. The moon complete one rotation about its axis in 27%, days.
INTEXT QUESTIONS (PAGE 197)
Q1. What is a planet? How many planets revolve around the sun?
Ans. The planets are the celestial bodies which revolve around a star, like the sun. Eight planets revolve around the sun.
Q.2. Name the planet which (i) is nearest to the sun (ii) is farthest from the sun (iii) supports life.
Ans. Mercury is the nearest and neptune is the farthest planet from the sun. The Earth is the planet of the sun which supports life.
Q.3. Name the planet which (i) revolves around the sun from east to west (ii) intersects the orbit of another planet?
Ans:-
(1) Venus revolves around the sun from east to west.
(ii) Pluto cuts the orbit of planet neptune.
Q.4. Name one planet that was predicted before its discovery.
Ans. Neptune was predicted before its discovery by U. J. Levessier in 1846.
Q.5.Name the planet having (i) largest number of moons (ii) a system of number of rings.
Ans. (i) The planet, Saturn having largest number of moons (30) and
(ii) it is also having a system of number of rings.
Q.6.What is Solar System? Name all the planets of Solar Systems in the increasing order of distance from the sun?
Ans:- Solar System consists of planets, comets, asteroids and meteors. Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune are the planets of solar system in the increasing order of distance from the sun.
TEXT BOOK EXERCISES
Q.1. Fill in the blanks by choosing correct words from the following list:
List: Meteorite, Pluto, Moon, Planets, Universe, Core, comet , Constellation
(1)The branch of science, which deals with the study of .......... is called astronomy
ii)The unburnt part of a meteor, which reaches the earth is called...............
(iii) The heavenly bodies, which revolve around the sun are called.........
(iv) The heavenly bodies, which revolve around the planets are called.............
(v) The orbit of .….......is not in the same place as that of the other planets.
(vi) A heavenly body with along tail, moving around the sum in an elliptical path is called ..........
(vii) In the .......... of the sun, hydrogen gas fuses with the liberation of the energy.
(vii) A group of stars, which resembles an animal or some other known object is called ..........
Ans.
(i) Universe;
(ii) meteorite;
(iii) planets;
(iv) moon;
(v) pluto;
(vi) comet;
(vii) core;
(viii) constellation.
Q.2. Statments given below are incorrect. Write correct statements.
(i) Halley's comet visit our solar system after 26 years.
Correct statement: Halley's comet visit our solar system after 76 years.
(ii) Helium as constitutes most of the atmosphere of the sun and stars.
Correct statement: Fusion of hydrogen and helium gas constitutes most of the atmosphere of the sun and stars.
(iii) Pole star is nearest to our solar system.
Correct statement: Pole star is situated on the axis of the earth.
(iv) Astronomers have divided the sky into 68 constellations.
Correct statement: Astronomers have divided the whole sky into 88 constellations.
(v) Metors on burning leave behind gold dust and light.
Correct statement: Meteors on burning leave behind a brilliant flash of light.
(vi) The orbit of the neptune is different from the orbits of the other planets in the solar system.
Correct statement: The orbit of the neptune creates some disturbance in the orbit of Uranus.
(vii) Mars is the second planet nearest to the sun.
Correct statement: Venus is the second planet nearest to the sun.
(viii) Moon revolves around the earth in 21% days.
Correct statement: Moon revolves around the earth in 27%, days.
Q.3. Answer the following questions :
(i) What is universe ? Name six different kinds of heavenly bodies found in the universe.
Aus.The vast unimaginable space which encompasses most distant stars, planets and anything else, which exists is called universe. The carth, the moon, the planets, the sun, the stars, the comets etc. are the different kinds of heavenly bodies found in the universe.
(ii)With the reference to the average distance from the sun, state:
(a) the serial number of the planet earth
(b) the average distance of the earth from the sun
(c) the time in which the sunlight reaches the earth?
Ans. (a) Earth is the third planet from the sun.
(b) The average distance of the earth from the sun is 149.6 million km.
(c) 8 minutes and 20 seconds sunlight takes the time to reach the earth.
(iii) (a) Name the natural satellite of the earth?
(b) In how many days does this satellite complete one revolution around the earth?
(c) In how many days does this satellite rotate around its own
(d) How does the gravity of this satellite compare with the earth?
(e) State the maximum temperature on the day side and minimum temperature on the night side of this satellite?
Ans. (a) The moon is the natural satellite of the earth.
(b) The moon completes one revolution around the Earth in 29% days
(c) The moon rotate around its own axis in 27⅓ days.
(d) The moon has no atmosphere and hence, no life on it. Its gravitational pull is one sixth on the earth.
(e) On the day side of the moon, the temperature could be as high be as low as 150°C. as 110°C and the temperature on the night side of the moon could
(iv) What do you understand by the following terms:
(a) New moon (b) full moon
Ans. (a) On the new moon day, the moon is between the sun and the earth and hence it is not visible. earth. Thus, the reflected light from the moon does not reach the
(b) On full moon day the earth is between the sun and the moon, such that the night side of the earth is facing the day side of the moon. This is called Full Moon day.
(v) (a) Define Solar System
Ans. The sun and its family, viz. planets, satellites, comets, asteroids etc. is called solar system.
(b) Name all the planets in the solar system in the order of their distance from the sun?
Ans. All the planets in the solar system in the order of their distance from the sun are:
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto.
(vi) (a) How many moons mars have?
Ans. The mars have 2 moons.
(b) Write the name of these moons.
Ans. Photos and Deimos are the two moons of the Mars.
(vii) What is a Comet? Why does a comet develop a tail while approaching the sun?
Ans. The bright "stars-like", objects with a long tail, approaching the sun in a highly elliptical orbit are called comets.
A comet develops a tail while approaching the sun because of the pressure of solar radiations.
(viii) What is star? What makes the star give about vast amount energy?
Ans. A self-luminous heavenly body in the space is called star. Stars produce heat energy and light energy due to the fusion of hydrogen.
(ix) (a) How are meteors different from stars?
The different between meteors and stars is:
Meteors
(i) The material of Meteors are mostly made of rocks, metals and dust.
(ii) The meteors produce heat energy and light energy due to the friction of the earth's atmosphere.
(iii) The meteors are very small pieces of rocks
(iv) The meteors last for a few seconds
Stars
(i) The material of the stars mostly consists of hydrogen and helium.
(ii) Star produce heat energy and light energy due to the fusion of hydrogen.
(iii) Stars are extremely big.
(iv) Stars last for billion of years seconds.
(b)How are meteors different from meteorites?
Ans. The different between meteors and meteorites is;
Meteor : Meteor is a heavenly body of very small mass, travelling in the space between the planets, when they reach the earth, gel burnt due to friction of the air. So, they shine in the sky as a bright streak of light lasting in moments.
Meteorites: Larger sized meteors are called meteorites. Being larger sized, they do not burn completely on reaching the earth atmosphere. So, they land on the earth and cause deep depression on the surface where they fall.
ADDITIONAL SHORT ANSWER TYPE
Q.1. Why the moon changes its shape?
Ans. As moon does not produce its own light. We see the moon because the sunlight falling on it gets reflected towards us. We, therefore see only that part of the moon, from which the light of the sun is reflected towards us.
Q.2. Why we do not see the stars during the day. Why are they visible only at night?
Ans. In fact, the stars are present in the sky during the day-time also. However, they are not visible then because of the bright sunlight.
Q.3. Whether Pluto is still a part of our solar system?
Ans. You might have heard from your parents that there are nine planets in our solar system. This was true till 2006. Pluto was the farthest planet from the sun. The International Astronomical Union (IAU) at a meeting held on 24 August 2006 adopted a new definition of planet Pluto does not fit in this definition. It is no more a planet of the solar system. So, the solar system now consists of only eight planets.
Q.4. The Earth revolves around the Sun. Does it make Earth a satellite of the Sun?
Ans. Generally, we use the term 'satellite' for the bodies revolving around a planet. Moon is a natural satellite of the earth. So, earth can be said to be a satellite of sun.
Q.5. If I am 13 years old, how many times have I gone round the sun.
Ans. As earth completes one revolution around the sun in one year. So I have 13 times gone round the sun.
Q.6. What do you understand by solar system? Give its constituents.
Ans. The sun and the celestial bodies, which revolve around it form consists of large number of bodies, such as, the solar system. planets, comets, asteroids and meteors. The attraction of the sun keeps all these objects revolving around it.
Q.7. Name the planet of sun in order of distance from sun.
Ans. The eight planets in their order of distance from the Sun are:
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
Q.8. What do you understand by orbit and period of revolution of a planet.
Ans. A planet has definite path, in which it revolve around the Sun. This path is called an orbit. The time taken by a planet to complete one revolution is called its period of revolution. The period of revolution increases as the distance of the planet from the sun increases.
Q.9. Is Sun a star?Explain.
Ans. The Sun is the nearest star from us. It is continuously emitting huge amounts of heat and light The Sun is the source of almost all energy on the earth. In fact, the sun is the main source of heat and light to all the planets that revolve around it.
Q.10. Write the applications of artificial satellites.
Ans. Artificial satellites have many practical applications. They are used in weather forecasting, television and radio transmission, communication and remote sensing.
Q.11. How big is the sun as compared to earth?
Ans. The diameter of the sun is 1,400,000km (approx).This diameter is 109 times the diameter of the earth. Thus, sun is, approximately, 300,000 times heavier than the earth.
Q12. What is a Light Year?
Ans. The distance travelled by the light at a speed of 300,000 km/s in one year (365 days) is called light year.
1 light year = Speed of light x 365 days
= 300,000 km/s x 365 x 24 x 60 × 60s
= 9.46 x 10¹² km
Q.13. Why do the stars appear to move from east to west?
Ans. It is because the earth rotates about its north-south axis from west to east. Thus, due to relative motion, all heavenly bodies (stars, planets, moon),etc., appear to move from east to west.
LONG ANSWER TYPE QUESTIONS
Q.14. Write short notes on the following-
(a) Asteroid
(b) Comets
(d) Meteorites
(c) Meteors
Ans. (a) Asteroids: There is a large gap in 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. Each asteroid has its own orbit and the orbits of all of them are spread over a large distance forming a band. Asteroids can only be seen through a large telescope.
(b) Comets : Comets are celestial bodies that revolve around the sun in highly elliptical orbits. However, their period of revolution round the sun is usually very large. A Comet appears, generally,as a bright head with a long tail. The length of the tail of the is always directed away from the sun. comet grows in size as it approaches the sun. The tail of a comet
(e) Meteors: At night, when the sky is clear and the moon is not there, you may sometimes see bright streaks of light in the sky. These are commonly known as shooting stars, although they are not stars. They are called meteors. A meteor is, usually, a small heavenly object moving around the sun. Occasionally, a meteor enters the earth's atmosphere. At that time it has a very high speed. The friction due to atmosphere heats up a meteor. It glows and evaporates in a very short time. That is why the bright streak appears for a very short time.
(d) Meteorites: Some meteors are so large that a part of them reaches the surface of the earth before they evaporate completely. These are called meteorites. Meteorites help scientists in investigating the nature of the material from which solar system was formed.
Q.15.How are Stars different from Planet?
Ans.
Stars
1. Stars have their own light.
2. Stars produce their own energy due to the fusion of hydrogen.
3. Stars appear to twinkle at night.
4. Stars have enormous mass.
5. Stars do not change their relative positon in the sky everyday.
6. Stars appear to move from east to west.
Planet
1.Planets do not have their own light.
2. Planets do not produce their own energy. They have to depends upon the energy of stars (Sun).
3. Planets do not twinkle at night.
4. Planets have insignificant mass, compared to the stars.
5.Planets changes their position in the sky on a daily basis.
6.Planets appear to rotate from the west to east (except venus) in the sky.
Q.16. What is star? What makes the star to give about vast amount of energy.
Ans. A self-luminous heavenly body in the space is called star. All stars are Gaint ball of hydrogen gas and this includes our sun also, which is a medium star. At the core of this giant hydrogen cloud, the temperature is from 2 million to 5 million degree celcius. At such a high temperature, the hydrogen gas fuses to form a heavier gas called Helium and this pattern goes on with the liberation of huge amount of heat and light energy. Thus, the fusion of hydrogen gas within the core of star give vast amount of energy.
Q.17. Write various uses of artificial satellites.
Ans. Various uses of artificial satellites are as follows:
1. They can be used to forecast weather.
2. They facilitate radio and television programme transmission.
3. Artificial satellites enable long distance telephone communication.
4. They help to locate mineral and metal deposits.
5. Artificial satellites fitted with telescopes and software programmes gather and process data on space phenomena, thus, enhancing our knowledge and understanding of the universe.
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