The topic, Planet: Earth in the solar system is mentioned in the CTET paper 2 geography syllabus. This topic is directly taken from class 6 NCERT Geography book. It is the first chapter of this book. I have covered all the important details from this chapter at examination prospective but If you want to read that complete chapter, you can download the PDF given at the end of this article.
Planet: Earth in the solar system
Night Sky Observations: Stars appear as tiny, twinkling lights due to their great distance. Do you know why can’t we see the moon and all those bright tiny objects during day time? It is because the very bright light of the sun does not allow us to see all these bright objects of the night sky.
Celestial bodies: The sun, the moon and all those objects shining in the night sky are called celestial bodies. Those who study the celestial bodies and their movements are called astronomers.
Stars: Some celestial bodies are very big 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. The sun is a star.
Full moon night or Poornima: The Full Moon, or Poornima, is the phase of the moon when it appears fully illuminated from Earth. This happens once a month when the Earth is positioned between the sun and the moon, allowing sunlight to fully reflect off the moon's surface, making it appear round and bright in the night sky.
New Moon (Amavasya): The New Moon, or Amavasya, is the phase when the moon is not visible from Earth. This occurs once a month when the moon is positioned between the Earth and the sun, causing the side of the moon facing Earth to receive no direct sunlight. As a result, the moon appears completely dark, and it’s the best time to observe stars and other celestial bodies in the night sky.
Constellations: While watching the night sky, you may notice various patterns formed by different groups of stars. These are called constellations. Ursa Major or Big Bear is one such constellation.
Saptarishi: One of the most easily recognisable constellation is the Saptarishi (Saptaseven, rishi-sages). It is a group of seven stars that forms a part of Ursa Major Constellation.
The Pole Star: The Pole Star, also known as the North Star or Polaris, is a prominent star that lies nearly in line with Earth’s rotational axis above the North Pole. This unique alignment means it appears almost stationary in the sky, making it a reliable reference point for navigation, especially in the Northern Hemisphere.
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Ancient navigators used the Pole Star to determine direction, as it always indicates true north. The Saptarishi constellation can help locate the Pole Star by following an imaginary line through two of its stars (called pointer stars) that point directly to it.
Planets: Some celestial bodies do not have their own heat and light. They are lit by the light of the stars. Such bodies are called planets. The word ‘planet’ comes from the Greek word “Planetai” which means ‘wanderers’.
The Solar System: The sun, eight planets, satellites and some other celestial bodies known as asteroids and meteoroids form the solar system. We often call it a solar family, with the sun as its Head.
The Sun: The sun is in the centre of the solar system. it is the our nearest star. It is huge and made up of extremely hot gases. It provides the pulling force that binds the solar system. The sun is the ultimate source of heat and light for the solar system. The sun is about 150 million km away from the earth. The light of the sun takes about eight minutes to reach the earth.
Planets: There are eight planets in our solar system. In order of their distance from the sun, they are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. An easy way to memorise the name of the planets in order of their distance from the sun is:
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Mercury is nearest to the sun. It takes only about 88 days to complete one round along its orbit. Venus is considered as ‘Earth’s-twin’ because its size and shape are very much similar to that of the earth. Pluto was reclassified as a dwarf planet in August 2006 by the International Astronomical Union.
Orbits: All eight planets of the solar system move around the sun in fixed paths. These paths are elongated or elliptical. They are called orbits.
The Earth: The earth is the third nearest planet to the sun. In size, it is the fifth largest planet. It is slightly flattened at the poles. That is why, its shape is described as a Geoid. Geoid means an earth-like shape. From the outer space, the earth appears blue because its two-thirds surface is covered by water. It is, therefore, called a blue planet.
Why is the earth a unique planet in the solar system?
Conditions favourable to support life are probably found only on the earth. The earth is neither too hot nor too cold. It has water and air, which are very essential for our survival. The air has life-supporting gases like oxygen. Because of these reasons, the earth is a unique planet in the solar system.
The Moon: The moon, Earth's only satellite, is one-quarter the size of Earth and 3,84,400 km away. It takes 27 days to orbit Earth and rotates in the same time, showing only one side. Neil Armstrong was the first man on the moon in 1969. Indian satellites like INSAT and IRS gather information and aid communication in space.
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A Human-made Satellite is an artificial body. It is designed by scientists to gather information about the universe or for communication. It is carried by a rocket and placed in the orbit around the earth. Some of the Indian satellites in space are INSAT, IRS, EDUSAT, etc.
Asteroids: Apart from the stars, planets and satellites, there are numerous tiny bodies which also move around the sun. These bodies are called asteroids. They are found between the orbits of Mars and Jupiter.
Meteoroids: The small pieces of rocks which move around the sun are called meteoroids. Sometimes these meteoroids come near the earth and tend to drop upon it. During this process due to friction with the air they get heated up and burn. It causes a flash of light. Sometimes, a meteor without being completely burnt, falls on the earth and creates a hollow.
Galaxy: A galaxy is a huge system of billions of stars, and clouds of dust and gases. There are millions of such galaxies that make the Universe. Milky Way or Akash Ganga is our galaxy.
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