CBSE Class 6 Social Science: The Earth in the Solar System NCERT Solutions

(a) The key differences between a planet and a star are:

• Star: Possesses its own heat and light. Stars are generally very large celestial bodies.
• Planet: Does not have its own light and heat; it derives them from a star. Planets are usually smaller than stars.

(b) The 'Solar System' refers to the Sun and the family of celestial bodies that revolve around it. This family includes eight planets, dwarf planets, asteroids, and comets, all bound by the Sun's gravitational pull. The Sun is considered the central and dominant body of this system.

(c) The planets, listed in order of their increasing distance from the Sun, are:

1. Mercury
2. Venus
3. Earth
4. Mars
5. Jupiter
6. Saturn
7. Uranus
8. Neptune

(d) The Earth is considered a unique planet primarily because it is the only planet known to harbor life. This is due to the presence of essential elements like oxygen and water in suitable proportions, along with a temperature range that supports life. Furthermore, about two-thirds of Earth's surface is covered by water, distinguishing it from other planets.

(e) We always see only one side of the Moon from Earth because the Moon's period of rotation on its own axis is approximately equal to its period of revolution around the Earth. This phenomenon is known as synchronous rotation, meaning it takes the Moon about 27 days to complete one spin and one orbit.

(f) The Universe is the vastest entity known, encompassing everything that exists. It is composed of numerous galaxies, each containing billions of stars, planets, and other celestial matter. Our existence is within this single, immense Universe.

(a) (iii) Venus. Venus is often called Earth's Twin because it is similar in size and shape to Earth.

(b) (ii) Earth. The order from the Sun is Mercury, Venus, and then Earth.

(c) (iii) Elongated path. Planets move around the Sun in elliptical (elongated) orbits.

(d) (ii) North. The Pole Star is located in the direction of the North Celestial Pole and helps in navigation.

(e) (ii) Mars and Jupiter. The asteroid belt, a region containing numerous asteroids, is located between the orbits of Mars and Jupiter.

(a) A group of stars forming various patterns is called a constellation.

(b) A huge system of stars is called galaxy.

(c) The moon is the closest celestial body to our earth.

(d) The Earth is the third nearest planet to the sun.

(e) Planets do not have their own heat and light.

(i) (d) month. A full moon occurs approximately once a month, about 29.5 days after the previous full moon.

(ii) (a) Amavasya. Amavasya is the Hindi term for the New Moon night.

(iii) (d) all of these. The Sun is a star, a celestial body, and the head of our Solar System.

(iv) (b) constellation. Ursa Major, also known as the Great Bear, is a prominent constellation.

(v) (c) Pluto. Pluto was reclassified as a dwarf planet in 2006.

(vi) (b) water. Earth is called the 'Blue Planet' because its surface is largely covered by water.

(i) The Amavasya night occurs about fifteen days after the Poomima night (full moon).

(ii) Stars are celestial bodies that are big, hot, and emit light.

(iii) The planets do not possess their own heat and light.

(iv) The Small Bear constellation is better known as the Saptarishi (or Little Dipper).

(v) The Greek word which is the origin of the word "planets" means wanderers.

(vi) Three planets having rings around them are Jupiter, Saturn, and Uranus. (Neptune also has faint rings).

(vii) Orbits are elongated fixed paths in which a celestial body always remains.

(viii) Venus is similar to the earth in its size and shape.

(ix) The shadows on the moon's surface are due to mountains and craters (and other topographical features).

(x) Meteoroids heat up and burn due to friction with the Earth's atmosphere.