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| The Earth In The Solar System |
- The sun, the moon and other shiny objects in the night sky are known as the celestial bodies.
- These celestial bodies are not visible during the daytime because of the brightness of sunlight.
Stars
- Stars are big and hot in nature. They are made of gases mostly hydrogen or helium. They emit a large amount of heat and light. Our sun is also a star.
- There are countless stars similar to the Sun. However, we do not feel their light and heat because of their farness from us.
- Constellations are the various pattern formed by various groups of stars. Constellations are a legacy of the human imagination. They are not formed by any natural occurrence.
- Ursa Major or the Big Dipper is one of the most prominent examples of constellations. In India, it is also known by the name of Saptarishi.
- In ancient time, people used to determine time and directions during the night with the help of stars.
- The North Star is also known as the Pole Star or Dhruva Tara, is taken as the reference star for determining direction. It indicates the north direction and remains in the same position throughout the year.
Planets
- Some celestial bodies do not generate their own heat and light. They lit by the light of stars and they revolve around the stars. Such celestial bodies are known as planets. Earth is one such example of a planet. It receives heat and light from the Sun.
- The word planet came from the Greek word "planetai" which means "wanderer" in English.
Satellites
- Some celestial bodies which do not generate their own heat and light, and lit by the light of a star but revolve around a planet are known as satellites. Out Moon is one such example of satellites.
Solar System
- The Sun, eight planets, their satellites and some other celestial bodies such as asteroids and meteoroids form our solar system.
The Sun
- Sun is in the centre of the solar system.
- It is made up of hot gases such as hydrogen and helium.
- It is the binding force behind the solar system.
- It is the ultimate source of heat and light in our solar system.
- It is about 149.6 million km away from the earth.
Planets
- There are eight planets which move around the Sun in a fixed path. This fixed path is known as the orbit.
- The eight planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
- Mercury is the nearest planet to our sun. It takes 88 days to complete its single rotation around the Sun.
- Till 2006, Pluto was also considered a planet but it is now classified as the dwarf planets. Other dwarf planets in our solar system are Ceres, Haumea, Makemake and Eris.
The Earth
- Earth is the third nearest planet to the sun.
- In size, Earth is the fifth largest planet in our solar system.
- It is not too far and not to close from the Sun, which makes its conditions optimum for life.
- The two-thirds of the Earth surface is covered by water, therefore, it is known as the Blue Planet.
The Moon
- Earth has only one moon.
- Its diameter is one-quarter of Earth diameter. Moon diameter is 3474.2 km.
- It is 384400 km away from the Earth.
- The moon moves around the earth in 27 days. It also takes exactly the same to complete one spin.
- It does not have life-supporting conditions, but similar to Earth, it has mountains, plains and depressions.
- On 21st July 1969, Neil Armstrong became the first man to step on the surface of the moon.
Artificial Satellites
- There are human-made satellites which revolve around the Earth in the same way as Moon revolves around the Earth.
- These artificial satellites are mostly used for communication or weather forecasting purpose.
Asteroids
- There are numerous tiny celestial bodies which move around the sun in a similar way as planets. These celestial bodies are known as asteroids.
- Asteroids are found between the orbit of Mars and Jupiter.
- Scientists believe asteroids are part of a planet which either exploded or failed to stick together.
Meteoroids
- Meteoroids are small pieces of rocks which move around the Sun.
- Sometimes, due to Earth's gravitation, they pull toward Earth. Upon their drop, they get heated and burn out due to their friction with the earth's atmosphere.
- Sometimes, they are not completely burnt, falls on the earth surface and creates hollow craters.
Our solar system is the part of the Milkyway Galaxy. It is also known as the Akash Ganga.
A galaxy is a system of billions of stars, planetary systems, and dust and gas cloud. There are millions of galaxy which together form our Universe.
Source: NCERT Class 6 Geography