Friday, November 29, 2013

8th CBSE Chapter-STARS AND THE SOLAR SYSTEM Solved Questions

 Q1. Define light year.

Ans. Light year is the distance travelled by the light in one year.

Q2. Name the star nearest to the earth after sun.

Ans. Proxima centuari.

Q3. Why do stars shine?

Ans. Stars are giant ball of gases in space that shine through the darkness and are held together by the
force of gravitation. These gasses are hydrogen and helium. Some of the hydrogen is converted into helium. A star shines due to this reaction nit’s core releasing energy that radiates into the outer space.

Q4. What are constellations?

Ans. Group of stars that make an imaginary shape in the night sky is called constellations. There are 88
constellations known so far. Examples ursa major, Ursa Minor, Orion, Aries cancer, Cassiopeia, Gemini, Leo.

Q5. Write short note on pole star.

Ans. Pole star rises in the east at night and sets in the west in the early morning. Pole star is situated
above the axis of rotation of the earth, so it appears stationary from the earth. So it is used for
navigation. Pole star shows north direction.

Q6. What is a galaxy?

Ans. Galaxies are huge collection of star, other celestial bodies, dust and gases. These celestial bodies
are held together by the force of gravitation. We also live in a galaxy. Our galaxy is known as the Milky
Way.

Q7. Why cannot we see the back side of the moon from the earth?

Ans. We cannot we see the back side of the moon from the earth because the time taken by the moon
to complete one rotation on its axis is same as that moon completes one revolution around the earth.

Q8. What do you understand by the waxing and waning of the moon?

Ans. When the moon grows we say it is waxing and when it shrinks back to a new moon it is said to be waning.

Q9. Why do we see the phases of the moon?

Ans. We see only that part of the moon which reflects the sunlight towards us. T he part of the moon
that reflects light keeps on changing daily. This happens because the moon revolves around the earth
and the earth along with the moon revolves around the sun. Therefore we see the phases of the moon.

Q10. What are craters?

Ans. Moon has depressions called craters. The moon surface is rocky and is covered with dust.

Q11.Define comets.

Ans. Comets are celestial objects that revolve around the sun in very long periods of revolution. A
comet appears like a ball of fire with long bright tail as it approaches the sun. The tail always points
away from the sun, and its size increases as it approaches the sun. The famous Haley’s comet appears
after every 76 years. It last appeared in 1986.

Q12. What are planets?

Ans. A Planet is a large round heavenly body that orbits a star and shines with light reflected from the
star. There are 8 planets in the solar system that revolve around the sun in elliptical orbits and they also
rotate about their own axes. They look bright to us but they do not twinkle like stars.

Q13. Write short note on Orion constellation.

Ans. This constellation can be seen in winters. It is also called the hunter. It ha 7 prominent stars that
represent the belt of hunter and four stars forms a quadrilateral. The brightest star Sirius is located near
to Orion.

Q14. Define solar system.

Ans. 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.

Q15. Explain with the help of diagram, different phases of the moon.

Ans. When the moon is in between the earth and the sun, we do not see the moon at all. It is called the
new moon (amavasya).

Two or three days after this, we see only a part of the moon. This is called the crescent moon.
Gradually, the shape of the moon becomes bigger and bigger, with in a week we see half of the moon,
This is called the first quarter.

When we see more than half of the moon, it is called the gibbous moon.

On the fifteenth day after the new moon, we see the full moon (purnima), when the earth comes
between the sun and the moon.

Thereafter the bright portion of the moon reduces, and 15 days after the full moon we again have the
new moon.

Q16. What are asteroids?

Ans. Asteroids are large gap between the orbits of mars and Jupiter. A large number of rocks called
asteroids lie in this space. The largest asteroid is Ceres. The size of asteroid varies from a kilometer to a
few hundred kilometers.

Q17. Define comets.

Ans. Comets are celestial objects that revolve around the sun in very long periods of revolution. A
comet appears like a ball of fire with long bright tail as it approaches the sun. The tail always points
away from the sun, and its size increases as it approaches the sun. The famous Haley’s comet appears
after every 76 years. It last appeared in 1986.

Q18. Give some applications of artificial satellites.

Ans. (a) Artificial satellites are very useful to us.
(b) They help in television and radio transmission.
(c) They help in telephone communication.
(d) They help us to study and forecast weather by sending cloud pictures to the earth, taken from space.
(e) They help in locating minerals and studying agricultural yields on the earth by photographing land from above. This is known as remote sensing which means collecting information from distance.
(f) They help scientist know more about the universe by collecting information about space.

Q19. Write short note on Orion constellation.

Ans. This constellation can be seen in winters. It is also called the hunter. It ha 7 prominent stars that
represent the belt of hunter and four stars forms a quadrilateral. The brightest star Sirius is located near
to Orion.

 Q20.. What is a galaxy?

Ans. Galaxies are huge collection of star, other celestial bodies, dust and gases. These celestial bodies
are held together by the force of gravitation. We also live in a galaxy. Our galaxy is known as the Milky
Way.

Q21. Define solar system.

Ans. 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.

Q22. Name the star nearest to the earth after sun.

Ans. Proxima centuari.

Q23. Why do stars shine?

Ans. Stars are giant ball of gases in space that shine through the darkness and are held together by the
force of gravitation. These gasses are hydrogen and helium. Some of the hydrogen is converted into
helium. A star shines due to this reaction in it’s core releasing energy that radiates into the outer space.

Q24. Why cannot we see the back side of the moon from the earth?

Ans. We cannot we see the back side of the moon from the earth because the time taken by the moon
to complete one rotation on its axis is same as that moon completes one revolution around the earth.

Q25. What do you understand by the waxing and waning of the moon?

Ans. When the moon grows we say it is waxing and when it shrinks back to a new moon it is said to be waning.

Q26. Why do we see the phases of the moon?


Ans. We see only that part of the moon which reflects the sunlight towards us. T he part of the moon
that reflects light keeps on changing daily. This happens because the moon revolves around the earth
and the earth along with the moon revolves around the sun. Therefore we see the phases of the moon.

Q27. What are craters?

Ans. Moon has depressions called craters. The moon surface is rocky and is covered with dust.

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