CHAPTER- 1 THE EARTH IN THE SOALR SYSTEM
NOTES
1. We can see the full moon about once a month. This is the night of the full moon or Purnima. Fifteen days later, it cannot be seen. This is the night of the new moon or Amavasya.
2. Celestial bodies– The Sun, the Moon, and all the objects that shine in the sky at night are called celestial bodies.
3. Star– Some celestial bodies are large in size and hot. They are made up of gases. They have their own heat and light, which they emit in large amounts. These celestial bodies are called stars.
4. Constellation– While looking at the night sky, you can see various shapes formed by different groups of stars, such as Ursa Major (Big Bear).
5. Pole Star– It always remains at the same position in the sky. The North Star indicates the north direction.
6. Planet– Some celestial bodies do not have their own light and heat. They shine by reflecting the light of stars. Such bodies are called planets.
- A planet is called "Planet" in English. It is derived from the Greek word Planete, which means wanderer or one that moves around.
7. Solar System– The word Solar means related to the Sun. Hence, the Sun's family is called the Solar System.
The Sun is the head of our Solar family.
A) Sun– The Sun is located at the center of the Solar System. It is the only source of light and heat for the Solar System. Even though it is the closest star to us, it is still very far from us. The Sun is approximately 150 million kilometers away from Earth.
B) Planets– There are eight planets in our Solar System. In order of their distance from the Sun, the planets are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
- Orbit– All eight planets of the Solar System revolve around the Sun in a fixed path. These paths are elliptical in shape and are called orbits.
C) Earth– Earth is the third planet from the Sun in terms of distance. It is the fifth largest planet in the Solar System. It is slightly flattened at the poles, which is why its shape is called Geoid. The term Geoid means Earth-like shape.
- Earth is neither too hot nor too cold. It has water and air, which are essential for life. That is why Earth is the most unique planet in the Solar System.
- From space, Earth appears blue in color. About two-thirds of its surface is covered with water. That is why it is called the Blue Planet.
D) Moon– Our Earth has only one natural satellite, the Moon. Its diameter is only one-fourth of Earth's diameter.
- Neil Armstrong was the first person to set foot on the surface of the Moon on July 20, 1969.
- The Moon completes one orbit around the Earth in approximately 27 days. In the same duration, it also completes one rotation on its own axis. As a result, we can see only one side of the Moon from Earth.
E) Asteroids– Besides stars, planets, and satellites, countless small celestial bodies also orbit the Sun. These bodies are called asteroids.
F) Meteoroids– Small pieces of rock that orbit around the Sun are called meteoroids.
G) Galaxy– A galaxy is a system of millions of stars, clouds, and gases.
8. Universe – Millions of galaxies come together to form the Universe.
- Its immense vastness is extremely difficult to imagine.
EXERCISE
Question- 1. Answer the following questions briefly.
(a) How does a planet differ from a star?
Answer- Some celestial bodies are very large and hot. They are made of gases. They have their own heat and light, which they emit in very large amounts. Such celestial bodies are called stars. The Sun is also a star.
Some celestial bodies do not have their own light and heat. They are illuminated by the light of stars. Such bodies are called planets. The Earth, on which we live, is a planet.
(b) What is meant by the Solar System?
Answer- The Sun, eight planets, satellites, and some other celestial bodies such as asteroids and meteoroids together form the solar system. We call it the solar family, whose head is the Sun.
(c) Name all the planets according to their distance from the Sun.
Answer- According to their distance from the Sun, the names of the planets are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
(d) Why is the Earth called a unique planet?
Answer- The Earth is called a wonderful planet for the following reasons:
1. Conditions suitable for life are found only on Earth.
2. The Earth is neither too hot nor too cold.
3. Water and air are present, which are essential for our life.
4. The air contains gases necessary for life, such as oxygen.
(e) Why do we see only one side of the moon always?
Answer- The Moon completes one revolution around the Earth in about 27 days. In about the same time, it also completes one rotation on its axis. As a result, we can see only one side of the Moon from the Earth.
(f) What is the Universe?
Answer- A galaxy is a system of millions of stars, clouds, and gases. Millions of such galaxies together form the universe. It is very difficult to imagine the vastness of the universe. We do not have exact information about its size, but we know that all of us are a part of this universe.
Question- 2. Tick the correct answer.
(a) The planet known as the "Earth's Twin" is
(1) Jupiter (2) Saturn (3) Venus
(b) Which is the third nearest planet to the sun?
(1) Venus (2) Earth (3) Mercury
(c) All the planets move around the sun in a
(1) Circular path (2) Rectangular path (3) Elongated path
(d) The pole Star indicates the direction to the
(1) South (2) North (3) East
(e) Asteroids are found between the orbits of
(1) Saturn and Jupiter (2) Mars and Jupiter (3) The Earth and Mars
Answer- (a)- (3) Venus,
(b)- (2) Earth,
(c)- (3) Elongated path,
(d)- (2) North,
(e)- (2) Mars and Jupiter
Question- 3. 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) A group of Stars forming various patterns is called a Constellation.
(b) A huge system of stars is called Galaxy.
(c) Venus is the closest Celestial body to our earth.
(d) Earth is the third nearest planet to the sun.
(e) Planets do not have their own Heat and Light.
