“Stars and the Solar System” is Chapter 15 taken from the JKBOSE textbook of Science for students of Class 8th. In the previous post, I provided you with Questions and Answers for Chapter 14 Friction. This post is about the Stars and the Solar System Class 8 Question Answers. Before we move on to solutions you must have your basics clear. So, let me begin by giving you a brief overview of what you have studied in this chapter.
Stars and the Solar System Class 8 Question Answers
Overview of Chapter
- WHAT ARE HEAVENLY BODIES OR CELESTIAL BODIES?
- WHAT IS THE UNIVERSE?
- WHAT IS ASTRONOMY?
- NIGHT SKY.
- Why are stars not visible during the daytime?
- How do stars emit light?
- The Sun.
- What are the units of measuring the distance of stars from the Earth?
- THE SOLAR SYSTEM.
- OTHER HEAVENLY BODIES.
INTRODUCTION: This chapter deals with the sun, planets and other heavenly bodies in the universe. Like earth there are seven other planets in the solar system, there are also several satellites, and other heavenly bodies like asteroids, comets, meteors and meteorites etc in the sky. In this chapter, we have studied all these things.
WHAT ARE HEAVENLY BODIES OR CELESTIAL BODIES? The objects which are present in the sky or outer space are termed celestial objects. Bodies like stars, planets, satellites, asteroids, comets and meteoroids are celestial objects. They are also called heavenly objects or bodies.
WHAT IS THE UNIVERSE? The vast unimaginable space which has stars, planets and other heavenly objects in it is termed the universe.
WHAT IS ASTRONOMY? The branch of science that deals with the study of the universe are called astronomy. It involves the study of methods and instruments used for the study of the universe.
NIGHT SKY: During day time we can see only the sun in the sky. But during the night time, we can see many celestial objects in the sky. On a clear moonless night, we can see about 3000 stars in the sky. Stars appear to twinkle in the sky. We can also see some other star-like objects in the sky which do not twinkle. These are planets. These revolve around the sun. Moon is the most prominent object which we can see in the night sky. Sometimes we can see a streak of light flashing in the night sky. These are meteors.
- Why are stars not visible during the daytime? The stars are not visible during the daytime because of the glare of sunlight. The sunlight is so strong that it suppresses the light coming from the stars, so we cannot see them in the daytime.
- How do stars emit light? Stars are giant balls of hydrogen gas. The core of this giant hydrogen cloud has a temperature between 2 million to 5 million degree Celsius. At such a high-temperature fusion of hydrogen gas takes place with the liberation of a huge amount of heat and light energy.
- The Sun: Sun is a medium-sized star around which our earth and all other planets revolve. It is the source of all the energy present on earth. It is a sphere of hot gases mainly hydrogen. The distance of the sun is about 150 million kilometres. The diameter of the sun is 1,400,000 km which is 109 times more than that of the earth.
- What are the units of measuring the distance of stars from the Earth? The distance between the stars is extremely large and it is not convenient to express it in kilometres. So, it is expressed in light years. One light year means the distance covered by light in one year.
1 light year = 9.46 × 1012 km = 9.46 × 1015 m
The distance travelled by light in one minute is called a light minute.
1 light minute = 18 × 106 km = 18 × 109 m
CONSTELLATIONS: The group of stars which appears to form a recognizable shape or pattern is termed a constellation. The stars in the constellation always remain together and as a result shape of the constellation always remains the same. Some important and well-known constellations are:
- Ursa Major Constellation (Great Bear, Big Bear, Big Dipper or Plough) Saptarishsi (India)
- Orion Constellation.
- Cassiopeia Constellation.
- Leo Major Constellation.
PLANETS: Planets are the celestial bodies which revolve around the Sun in closed elliptical paths termed orbits. There are eight planets in the solar system. These are
- Mercury (Budha)
- Venus (Shukra)
- Earth (Prithvi)
- Mars (Mangal)
- Jupiter (Brihaspati or Guru)
- Saturn (Shani)
- Uranus (Arun or India)
Mercury is the smallest planet in the solar system whereas Jupiter is the biggest planet in the solar system.
THE SOLAR SYSTEM: The Sun with its family of planets, satellites, asteroids, comets and meters which revolve around the sun is called the solar system. Sun is at the centre of the solar system and all other objects are revolving around it.
OTHER HEAVENLY BODIES: The Solar system also has some other objects in it besides the Sun, planets and their satellites. These are asteroids, comets and meteoroids.
- Asteroids: Asteroids are small celestial objects which revolve around the Sun between the orbits of Mars and Jupiter. They can e seen only with help of a telescope.
- Comets: These are small celestial bodies which are made up of gases and dust and revolve around the sun in highly elliptical orbits. They become visible when they come close to Sun.
- Meteors: A meteor is seen as a bright streak of light that flashes for a moment across the sky. It is commonly called a shooting star.
- Meteorite: Meteorite is a meteor which does not burn up completely on entering the atmosphere and lands on the earth.
Stars and the Solar System Chapter 15 Questions
- Fill in the blanks by choosing the correct words from the following list:
List: meteorite, pluto, moon, planets, universe, core, comet, constellation
(i) The branch of science that deals with the study of the universe are called astronomy.
(ii) The unburnt part of a meteor which reaches the earth is called a meteorite.
(iii) The heavenly bodies which revolve around the sun are called planets.
(iv) The heavenly bodies which revolve around the planets are called a satellite.
(v) The orbit of pluto is not in the same plane as that of the other planets.
(vi) A heavenly body with a long tail, moving around the sun in an elliptical path is called a comet.
(vii) In core the of the sun, hydrogen gas fuses with the liberation of energy.
(viii) A group of stars which resembles an animal or some other known object is called a constellation.
- The statements given below are incorrect. Write correct statements.
(i) Halley’s comet visits our solar system after 26 years.
Ans. Halley’s comet visits our solar system after 76 years.
(ii) Helium gas constitutes most of the atmosphere of the sun and the stars.
Ans. Hydrogen gas constitutes most of the atmosphere of the sun and the stars.
(iii) Pole star is nearest to our solar system.
Ans. Alpha Centauri is nearest to our solar system.
(iv) Astronomers have divided the sky into 68 constellations.
Ans. Astronomers have divided the sky into 88 constellations.
(v) Meteors on burning leave behind gold dust and light.
Ans. Meteors on burning leave behind dust and light.
(vi) The orbit of Neptune is different from the orbits of the other planets in the solar system.
Ans. The orbit of Pluto is different from the orbits of the other planets in the solar system.
(vii) Mars is the second planet nearest to the sun.
Ans. Venus is the second planet nearest to the sun.
(viii) Moon revolves around the earth in days.
Ans. The moon revolves around the earth in days.
- Answer the following questions:
(i) What is the universe? Name six different kinds of heavenly bodies found in the universe.
Ans. The vast unimaginable space which has stars, planets and other heavenly objects in it is termed the universe. The six different kinds of heavenly bodies found in the universe are stars, planets, asteroids, comets, moons and meteoroids etc.
(ii) With the reference to the average distance from the sun state:
a) The serial number of the planet earth.
Ans. The serial number of the planet earth is third.
b) The average distance of the earth from the sun.
Ans. The average distance of the earth from the sun is 150 million kilometres.
c) The time in which the sunlight reaches the earth.
Ans. The sunlight takes 8.3 minutes to reach the earth.
(iii) a) Name the natural satellite of the earth.
Ans. Moon is the natural satellite of the earth.
b) In how many days does this satellite complete one revolution around the earth?
Ans. The moon takes days to complete one revolution around the earth.
c) In how many days does this satellite rotate around its own axis?
Ans. The moon takes days to complete one rotation on its own axis.
d) How does the gravity of this satellite compare to the earth?
Ans. The mass of the earth is 100 times more than that of the moon. So gravitational pull on the earth is greater than that of the moon. The gravity on the moon is one-sixth of the gravity on the earth.
e) State the maximum temperature on the day side and minimum temperature on the night side of this satellite.
Ans. The temperature of the moon on the day side could be as high as 110°C while the temperature on the night side of the moon could be as low as -150° C.
(iv) What do you understand by the following terms?
a) New Moon
Ans. The day on which the moon is not visible at all is called the new moon day. It comes on the fifteenth day after the full moon day.
b) Full moon.
Ans. The day on which the complete day side of the moon is visible is called full moon day. It comes on the fifteenth day after the new moon day.
(v) a) Define the Solar system.
Ans. The Sun with its family of planets, satellites, asteroids, comets and meters which revolve around the sun is called the solar system.
b) Name all the planets of the solar system in the order of their distance from the sun.
Ans. The name of the planets in order of their distance from the sun is as under:
1) Mercury 2) Venus 3) Earth 4) Mars 5) Jupiter 6) Saturn 7) Uranus 8) Neptune.
(vi) a) How many moons do mars have?
Ans. Mars has two moons.
b) Write the names of these moons.
Ans. The names of these moons are Photos and Deimos.
(vii) What is a comet? Why does a comet develop a tail while approaching the sun?
Ans. Comet is a small celestial body which is made up of gases and dust and revolves around the sun in a highly elliptical orbit.
While approaching the sun the gases of the comet start vaporising which gives out a blaze due to sunlight and it appears to us that comes has a tail.
(viii) What is a star? What makes the star give about a vast amount of energy?
Ans. Star is a celestial body which has its own heat and light.
The fusion reaction at the core of a star which converts hydrogen into helium makes the star give out a vast amount of energy.
(ix) a) How are meteors different from stars?
|A METEOR (SHOOTING STAR)
|1. The material of the stars mostly consists of hydrogen and helium.
|1. The material of a shooting star is mostly made of rocks, metals and dust.
|2. Stars produce heat energy and light energy due to the friction of the earth's atmosphere.
|2. The shooting stars produce heat energy and light energy due to the fusion of hydrogen.
|3. Stars are extremely big.
|3. The shooting stars are very small pieces
|4. Stars last for billions of years.
|4. The shooting stars last for a few seconds.
b) How are meteors different from meteorites?
|1. Meteors are the small pieces of stones or metals which enter into the earth’s atmosphere from outer space.
|1. They are big stones or metals which survive and reach the surface of the earth.
|2. They are small in size.
|2. They are big and can weigh up to several hundred tonnes.
|3. They don’t affect the surface of the earth due to their small size
|3. They can form craters on the surface of the earth.
That’s all about Stars and the Solar System Class 8 Question Answers. Hope it has helped. Do share your views about this post in the comment section below.