The DAV Class 8 Science Solutions and DAV Class 8 Science Chapter 17 Question Answer – Stars and Solar System are essential study tools for DAV public school students in Class 8.
DAV Class 8 Science Ch 17 Question Answer – Stars and Solar System
DAV Class 8 Science Ch 17 Solutions – Stars and Solar System
Something To Know
A. Fill in the blanks:
Question 1.
The spiral shaped galaxy in which our solar system is located is known as the ________ .
Answer:
Milky way
Question 2.
The various shapes of the bright part of the moon as seen by us during the month are called ________ of the moon.
Answer:
phases
Question 3.
The temperature on moon ranges from at ‘noon’ to ________ at ‘night’.
Answer:
100°C and -173°C
Question 4.
The planet known to have the largest number of natural satellites at present is ________ .
Answer:
Saturn
Question 5.
The comet, which Visits’ the earth every 76 years, is the ________ .
Answer:
Haley’s Comet
Question 6.
Asteroids are found between the orbits of ________ and ________ .
Answer:
Mars, Jupiter
B. Match the following:
| Column I | Column II |
| (1) Star nearest to the Earth | (a) Orion |
| (2) Brightest star in the night sky | (b) Sun |
| (3) Star which appear stationary from the earth | (c) Ceres |
| (4) Constellation | (d) Pole star |
| (5) The largest asteroid | (e) Geo-stationaxy satellite |
| (6) Global communication | (f) Sirius |
Answer:
| 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-stationaiy satellite |
C. Tick (✓) the correct option:
Question 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?
(a) 20 years
(b) 10 years
(c) 5 years
(d) 4.3 years
Answer:
(a) 20 years
Question 2.
Three stars A, B and C are observed in the night sky. The colours of these stars are-
Star A: Blue colour
Star B: Red colour
Star C: White colour
The correct sequence, in terms of increasing order of their surface temperature is—
(a) Star A > Star B > Star C
(b) Star A = Star B = Star C
(c) Star B > Star C > Star A
(d) Star B < Star C < Star A
Answer:
(d) Star B < Star C < Star A
Question 3.
Stars like the Sun appear to move from east to west around the earth. This means that earth rotates from-
(a) West to East
(b) East to West
(c) North to South
(d) South to North
Answer:
(a) West to East
Question 4.
Phases of moon are observed because-
(a) The moon does not reflect sunlight at all.
(b) It is only sunlight, reflected by some parts of the moon that reaches the earth.
(c) The shadow of the earth falls on the moon.
(d) Only some parts of moon can emit light.
Answer:
(b) It is only sunlight which is reflected by some parts of the moon that reaches the earth.
Question 5.
The change in seasons on the earth occurs because-
(a) The distance between the sun and the earth is not constant.
(b) The axis of rotation of the earth is tilted with respect to its orbit.
(c) Earth’s atmosphere has an ozone layer.
(d) The axis of rotation of the earth is perpendicular to the plane of its orbit.
Answer:
(d) The axis of rotation of the earth is tilted with respect to its orbit.
Question 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?
(a) Position A
(b) Position C
(c) Position B
(d) Position D
Answer:
(a) Position A
D. Answer the following questions in brief:
Question 1.
Name the first two stars closest to us.
Answer:
Sun, Sirius
Question 2.
Name the brightest star in the sky.
(a) During day time
(b) During night
Answer:
(a) Sun
(b) Alpha Centauri
Question 3.
Identify the planet with the help of the given clue.
(a) Largest planet
(b) Closest to the sun
(c) This planet has two moons named, Phobos and Deimos
(d) Red planet
(e) Has a unique and special system of rings
(f) Has the largest number of moons
(g) Often known as morning or evening star
(h) Named after the Roman Sea god
Answer:
(a) Jupiter
(b) Mercury
(c) Mars
(d) Mars
(e) Saturn
(f) Saturn
(g) Venus
(h) Neptune
Question 4.
Define the following:
(a) Milky way
(b) Celestial objects
(c) Pole Star
(d) Constellation
(e) Asteroids
(f) Geo-stationary satellites
(g) Comets
(h) Light year
(i) Meteors
(j) Meteorites
Answer:
(a) The spiral shaped galaxy containing our Solar System is called the Milky Way.
(b) Natural objects that exist in outer space are called celestial objects.
(c) The star which appears stationary when seen from the earth.
(d) A group of stars which makes a recognizable shape or pattern is called a constellation.
(e) The minor celestial objects which move around the sun between the orbits of Mars and Jupiter are called asteroids.
(f) Geostationary satellites appear to remain fixed with respect to a particular point on the earth.
(g) These are the celestial bodies which move around the sun in highly elliptical orbit.
(h) The distance travelled by light in one year is called a light year.
(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.
(j) A piece of rock which falls on the earth from outer space is called meteorite.
Question 5.
Name the visible layer of the sun. Give an estimate of its temperature.
Answer:
The visible layer of the Sun is called the photosphere. Its temperature is 6,000 K.
E. Answer the following questions:
Question 1.
How is Pole Star located in the sky? Explain with a diagram.
Answer:
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.
Question 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
Answer:
(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.
Question 3.
Identify, and name the constellations X, Y and Z and answer the following questions.
(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’.
Answer:
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
Question 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.
(c) The shape and size of bright side of moon appears to change (gradually) every day.
(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.
Answer:
(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.
Question 5.
State, in brief, how artificial satellites are used in transmitting television programmes over large distances.
Answer:
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.
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.
Question 1.
State the values displayed by the school counsellor.
Answer:
Using real life examples to motivate the students
Question 2.
Name any two celestial objects, other than moon, which do not have their own light.
Answer:
Mars, Venus
Question 3.
Have a group discussion on the importance of “having the right company’ specially during the ‘teen years’.
Answer:
Do it yourself
Something To Do
Question 1.
Visit any of the ancient astronomical observation built by Maharaja Jai Singh (of Jaipur) at Delhi (Jantar Mantar), Jaipur, Mathura, Ujjain or Varanasi. Try to learn about the instruments and techniques used by astronomers of those times.
Answer:
Do it yourself
Question 2.
Obtain information about the different Indian satellites and their significant uses.
Answer:
Do it yourself.
Question 3.
If possible, visit a planetarium. There are planetariums in many cities. In a planetarium, one can see the motion of stars, planets and constellations on a large dome.
Answer:
Do it yourself.
Question 4.
Observe the sky on a clear night and try to locate the Pole Star and some other star patterns you know of. Also, learn to identify planets visible to the unaided eye.
Answer:
Do it yourself.
Question 5.
Select any one planet from the eight listed planets. Collect as much information about this planet as you can. (Use internet resources/encyclopedia, etc.). Prepare a report. Tty to give details about the following in your report.
(a) Discovery of this planet
(b) Its special features, if any.
(c) Would human beings be able to survive on this planet?
Answer:
Do it yourself.
DAV Class 8 Science Chapter 17 Solutions – Stars and Solar System Important Questions and Answers
I. Fill in the blanks:
Question 1.
A ________ emits it own light.
Answer:
Star
Question 2.
A planet or a satellite reflects the light of the ________ .
Answer:
Star
Question 3.
We live in the ________ galaxy.
Answer:
Milky way
Question 4.
________ has rings around it.
Answer:
Saturn
Question 5.
No moon is visible on a ________ moon day.
Answer:
New
Question 6.
The planet with the least density is ________ .
Ans.
Saturn
II. Tick the correct answer:
Question 1.
Which of the following is the largest planet?
(a) Jupiter
(b) Saturn
(c) Uranus
(d) Neptun
Answer:
(a) Jupiter
Question 2.
What is the position of the earth from sun?
(a) First
(b) Second
(c) Third
(d) Fourth
Answer:
(c) Third
Question 3.
Which is the farthest planet from the sun?
(a) Uranus
(b) Neptune
(c) Pluto
(d) Saturn
Answer:
(b) Neptune
Question 4.
How many planets are there in the solar system?
(a) 6
(b) 7
(c) 8
(d) 9
Answer:
(c) 8
Question 5.
Which of these is a Jovian planet?
(a) Mercury
(b) Mars
(c) Jupiter
(d) Venus
Answer:
(c) Jupiter
Question 6.
Which of these is a terrestrial planet?
(a) Jupiter
(b) Saturn
(c) Uranus
(d) Earth
Answer:
(d) Earth
III. Answer the following questions:
Question 1.
What is a light year?
Answer:
The distance covered by light in one year is called a light year. One light year is equal to 9.4 x 1012 m.
Question 2.
Why do different stars appear of different colours?
Answer:
The colour of a star depends on its surface’s temperature. Stars with lower temperature appear red, those with high temperature appear white and the stars with very high temperature appear blue.
Question 3.
What do you understand by constellation?
Answer:
A group of stars appear to form some kind of pattern. Such groups of stars are called constellations. We can see certain recognizable patterns in different constellations.
Question 4.
What are the main types of planets?
Answer:
Planets can be divided into two categories:
- Terrestrial Planets: These are smaller in size and are made up of rocks. Mercuiy, Venus, Earth and Mars are terrestrial planets.
- Jovian Planets: These are very large in size and are mainly made up of gases. Jupiter, Saturn, Uranus and Neptune are the Jovian planets.
Question 5.
Write a brief note on Jupiter.
Answer:
This is the largest planet in the solar system. Its volume is 1300 times the volume of the earth. Jupiter is mainly composed of hydrogen and helium. Its cloud cover is made up of methane (in gaseous form) and some ammonia in crystalline form. There are 28 moons of Jupiter.
Question 6.
What is a comet?
Answer:
Comets are relatively small and icy celestial bodies. When a comet comes near the sun, some ice turns into gas. This leaves a long trail which appears as the tail of the comet.
IV. Projects:
Question 1.
Use balloons and papier-mache to make a model of the solar system. Display it in your classroom.
Answer:
Do it yourself
Question 2.
Write the names of five constellations and describe the shapes formed by them.
Answer:
Do it yourself