Chapter 1 The Earth in the Solar System

Chapter Review: ▸ The Sun, the moon all those objects shining in the sky are called celestial bodies.
▸ Celestial bodies which have their own heat and light are called Stars.
▸ The Sun is a Star.
▸ Various patterns formed by different groups of stars are called constellations e.g. Ursa Major or Big Bear.
▸ The Small Bear or Saptarishi is a group of seven stars.
▸ The North Star indicates the North direction. It is also called the Pole Star.
▸ We can locate the position of the Pole Star with the help of the Saptarishi.
▸ Some Celestial bodies which do not have their own heat and light and glow by the light of the stars are called planets.
▸ The moon that we see in the sky is a satellite.
▸ Solar system l The sun, nine planets satellites, asteroids and meteoroids form the solar system.
▸ The Sun l The sun is in the center of the solar system.
▸ It is made up of extremely hot gases.
▸ The sun is about 150 million km away from the earth.
▸ Planets l There are nine planets in our solar system.
▸ The nine planets are Mercury, Venus, Earth, Mars, Jupiter, Uranus, Neptune and Pluto.
▸ Planets move around the sun in a fixed orbit.
▸ Mercury is the nearest planet.
▸ Pluto is the farthest planet.
▸ A new planet 2003 UB313 has been discovered. It is bigger than Pluto and is farthest from the sun.
▸ Earth l It is the third nearest to the sun and fifth largest planet of our solar system.
▸ The earth is a unique planet because it supports life.
▸ It is also called the blue planet.
▸ It’s shape is Geoid.
▸ The Moon l It is only satellite of the earth.
▸ Its diameter is one-quarter of the earth.
▸ It is about 3.84,400 km. away from us.
▸ It moves around the earth in about 27 days.
▸ Only one side of the moon is visible to us on the earth.
▸ No life exists on moon as it has neither water nor air.
▸ Asteroids l They are numerous tiny bodies which move around the sun between the orbits of Mars and Jupiter.
▸ The largest asteroid is the Ceres.
▸ Meteoroids l The small pieces of rocks which move around the sun are called meteoroids.
▸ Our solar system is a part of Milky Way galaxy.
▸ Milky Way galaxy was named Akash Ganga.
▸ There are millions of galaxies that make the Universe.

Textbook Questions

Question1. Answer the following questions briefly.
(a) How does a planet differ from a star?
(b) What is meant by the ‘Solar System’?
(c) Name all the planets according to their distance from the sun.
(d) Why is the Earth called a unique planet?
(e) Why do we see only one side of the moon always?
(f) What is the Universe?
Answer: (a) Differences between a planet and a star:

Planet Star
A planet does not have its own light and heat. It derives its light from a star.
A planet is usually smaller than stars.
A star possesses its own heat and light.
Stars are very huge objects compared to a planet in general.

(b) The term Solar System refers to the “family” of the
Sun. The Sun is a star around which eight planets, among other celestial objects, revolve in orbits. This whole system of bodies is called the Solar System. The Sun is the “head” of this system.
(c) The list of planets in the order of their distance from the Sun is as follows:
(i) Mercury (ii) Venus
(iii) Earth (iv) Mars
(v) Jupiter (vi) Saturn
(vii) Uranus (viii) Neptune
(d) The Earth is regarded as a unique planet because of the following reasons:
▸ It is the only planet known to support life. It has oxygen and water present in proportions that allow life to thrive.
▸ It also has a temperature range that supports life.
▸ The proportion of water present is about two-thirds of the surface of earth when compared to land.
(e) One revolution of the moon around the earth takes about 27 days. Incidentally, the moon’s rotation about its own axis also takes nearly the same time. One day of the moon is equal to 27 Earth days. So only one side of the moon can be seen from the earth.
(f) The Universe is the largest unit in which we live. It is a collection of galaxies. There is only one Universe, and everything that exists, exists in this Universe itself.

Question2. Tick the correct answer.
(a) The planet known as the “Earth’s Twin” is
(i) Jupiter (ii) Saturn (iii) Venus.
(b) Which is the third nearest planet to the sun?
(i) Venus (ii) Earth
(iii) Mercury.
(c) All the planets move around the sun in a
(i) Circular path (ii) Rectangular path
(iii) Elongated path.
(d) The Pole Star indicates the direction to the
(i) South (ii) North
(iii) East.
(e) Asteroids are found between the orbits of
(i) Saturn and Jupiter (ii) Mars and Jupiter
(iii) The Earth and Mars.
Answer: (a)—(iii), (b)—(ii), (c)—(iii), (d)—(ii), (e)—(ii).

Question3. Fill in the blanks.
(a) A group of ……… forming various patterns is called a ……… .
(b) A huge system of stars is called ……… .
(c) ……… is the closest celestial body to our earth.
(d) ……… is the third nearest planet to the sun.
(e) Planets do not have their own ……… and ……… .
Answer: (a) stars, constellation (b) galaxy
(c) The moon (d) The earth
(e) heat, light.

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