Chapter 17| Stars And Solar System | Class- 8 DAV Science Solutions

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DAV Class- 8 | Stars and Solar System Question and Answer

Something To Know

A. Fill in the blanks:

1. The spiral shaped galaxy in which our solar system is located is known as the Milky Way.

2.The various shapes of the bright part of the moon as seen by us during the month are called Phases of the moon.

3. The temperature on moon ranges from 100 °C at ‘noon’ to -173 °C at ‘night’.

4. The planet known to have the largest number of natural satellites at present is saturn.

5.The comet, which ‘visits’ the earth every 76 years, is the Haley’s Comet.

6. Asteroids are found between the orbits of Mars and Jupiter.

B. Match the following statements:

Ans:

Column I	Column II
(1) Star nearest to the Earth	(b)Sun
(2) Brightest star in the night sky	(f) Sirius
(3) Star which appear stationary from the earth	(d) Pole Star
(4) Constellation	(a)Orion
(5) The largest asteroid	(c)ceres
(6) Global Communication	(e)Geo-Stationary Satellite

C. Tick the correct Option:

1.A star is twenty light years away from the earth. Suppose it brightens up suddenly today. After how much time shall we see this change?

Ans:20 Years

2.Three stars A, B and C are observed in the night sky. The colours of these stars are—Star

Ans. Star B < Star C < Star A

3.Stars like the Sun appear to move from east to west around the earth. This means that earth rotates from—

Ans. West to East

4. Phases of moon are observed because—

Ans. It is only sunlight which is reflected by some parts of the moon that reaches the earth.

5. The change in seasons on the earth occurs because—

Ans. The axis of rotation of the earth is tilted with respect to its orbit.

6. The diagram shows the various positions of a comet in its orbit. In which position will the tail of the comet appear to be the longest?

Ans: Position A

D. Answer the following questions in brief:

1.Name the first two stars closest to us. Ans. Sun, Sirius

2. Name the brightest star in the sky.

(a) During day time	(b) During night
(a) Sun	(b) Alpha Centauri

3. Identify the planet with the help of the given clue.

(a) Largest planet	(a) Jupiter
(b) Closest to the sun	(b) Mercury
(c) This planet has two moons named, Phobos and Deimos	(c) Mars
(d) Red planet	(d) Mars
(e) Has a unique and special system of rings	(e) Saturn
(f) Has the largest number of moons	(f) Saturn
(g) Often known as morning or evening star	(g) Venus
(h) Named after the Roman Sea god	(h) Neptune

4. Define the following:

Ans.

Milky Way : (a) The spiral shaped galaxy containing our Solar System is called the Milky Way.

Celestial objects: (b) Natural objects that exist in outer space are called celestial objects.

Pole Star (c) The star which appears stationary when seen from the earth.

Constellation :(d) A group of stars which makes a recognizable shape or pattern is called a constellation.

Asteroids (e) The minor celestial objects which move around the sun between the orbits of Mars and Jupiter are called asteroids.

Geostationary satellites (f) Geostationary satellites appear to remain fixed with respect to a particular point on the earth.

Elliptical orbit (g) These are the celestial bodies which move around the sun in highly elliptical orbit.

Light year (h) The distance travelled by light in one year is called a light year.

Meteor (i) A piece of rock, or metal, that burns and glows brightly in the sky when it enters the earth’s atmosphere, is called meteor.

Meteorite (j) A piece of rock which falls on the earth from outer space is called meteorite.

5. Name the visible layer of the sun. Give an estimate of its temperature.

Ans. The visible layer of the Sun is called the photosphere. Its temperature is 6,000 K.

E. Answer the following questions

1.How is Pole Star located in the sky? Explain with a diagram.

Ans. Locate the Big Dipper in the northern sky. The two stars at the top are called pointers. The line joining these two stars points towards the Pole Star.
Ursa Major

2. Differentiate between the following by giving examples: (a) Stars and constellation (b) Stars and planets (c) Terrestrial planets and Jovian planets (d) Artificial and natural satellites

Ans. (a) Star is a single unit, while a constellation is composed of many stars. Sirius is a star, while Orion is a constellation.

(b) Stars have their own light, while planets do not have their own light. Alpha Centauri is a star, while Mars is a planet.

(c) Terrestrial planets are made up rocks, while Jovian planets are made up of gases. Mars is a terrestrial planet, while Jupiter is a Jovian planet.

(d) Artificial satellites are man-made, while natural satellites are formed through natural processes. Moon is a natural satellite, while Aryabhata is an artificial satellite.

3. Identify, and name the constellations X, Y and Z and answer the following questions.

Constellabon Cantellabon v Conseellabon (a) Name the constellation that can be used to locate star Sirius.

(b) Name the constellation that can be used to locate the Pole Star.

(c) Name the constellation visible during the (i) spring season, (ii) winter season. (d) Name the stars A and B in the constellation marked as ‘X’.

Ans. X is Orion, Y is Big Dipper and Z is Cassiopeia (a) Orion (b) Big Dipper (c) Ursa Major is visible during spring season, while Cassiopeia is visible during winter season. (d) A is Betalgeuse, and B is Riget

4. Give reasons for the following:

(a) Uranus is observed to have a blue green’ colour.

(b) Venus is the hottest planet even though mercury is closest to the sun.

(d) A star appears to rise four minutes earlier in the sky every day than the previous day.

(e) Comets become visible only when they are near the sun.

Ans. (a) Uranus appears to have a blue green colour because of presence of methane in its cold and clear atmosphere.

(b) There is very high percentage of carbon dioxide in the atmosphere of Venus. This created greenhouse effect making Venus the hottest planet.

(c) The period of rotation and revolution of the moon is same. Due to this relative position of the earth, the sun and the bright portion of the moon keeps on changing every day. Hence, the shape and size of the bright side of moon appears to change gradually every day.

(d) This happens because of revolution and rotation of the earth. The apparent position of the star changes on a daily basis due to this. (e) Comets are very small. But they emit a trail of vapour when they come closer to the sun. The ‘tail’ of the comet becomes longer when it comes closer to the sun. Due to this, a comet becomes visible only when it is near the sun.

5. State, in brief, how artificial satellites are used in transmitting television programmes over large distances.

Ans. A satellite receives signal from a ground station on the earth. The amplifiers in the satellite first amplify this signal. After that, the satellite re-transmits the signal back to a receiving station on the earth.

F. Value based Questions

Sumit was an extremely lively boy, always respectful towards his elders and teachers. He was also academically brilliant and always scored well. However, when he was in Class IX, his behaviour would often reflect some undesirable qualities. The school counsellor decided to talk to him. She told him that just as the moon reflects the light of the sun to illuminate itself, we too, can idolize inspirational sources and try to imbibe and radiate their positive energy. This way we cannot only brighten up our lives but also of the ones around us. Sumit understood her point and promised to tread on the path of improvement.

1. State the values displayed by the school counsellor.

Ans. Using real life examples to motivate the students 2. Name any two celestial objects, other than moon, which do not have their own light. Ans. Mars, Venus 3. Have a group discussion on the importance of ‘having the right company’ specially during the ‘teen years. Ans. Do it yourself

Something To Do

Do it yourself

Chapter 17| Stars and Solar System | Class- 8 DAV Science Solutions