Category : 5th Class
This lesson will help you to:
QUICK CONCEPT REVIEW
As we all know we live on earth. Earth is a planet. We also see birds, trees and animals that live on earth. But have you ever thought that, the universe contains earth only or there are other things also besides the earth?
There is unlimited place around the earth and this space is called universe. It includes stars, planets and other things.
There are other planets and satellites which revolve around the sun and together them from the solar system.
The sun and the planets moons, asteroids, comets and the other things revolving around the sun together constitute the solar system.
FORMATION OF SOLAR SYSTEM
The formation of solar system began some 4.6 billion years ago when a cloud of dirt and gases was formed. This cloud started collapsing into its centre due to gravitational force. The sun was formed at the centre while the rest flattened into a disc of loose dust, out of which the planets, asteroids and solar bodies were formed.
In this chapter we shall about the sun and its family members.
Sun is a star. As we all know that it gives us light and heat. Our life depends upon it.
The distance of sun from earth is greater than the distance of earth from moon. The things start appearing smaller than their actual size as they start moving away from us. So as the sun is at more distance as compared to the moon from earth, it looks smaller in size. There are stars bigger than the sun but they are not visible to us as they are very far away from us.
Sun is at the centre of the solar system and all the planets revolve around it. The circles or the path followed by the planets to revolve around the sun is called an orbit. All the planets move in their own orbits.
The earth takes 365 days to take one round of the sun. The sun accounts for more than 99% of the mass of the solar system. It mainly contains hydrogen and helium. The light from the sun reaches our earth in eight and a half minutes.
1. MERCURY: It is the nearest planet to the sun and hence it is the hottest. It is also the smallest planet.
2. VENUS: It is the closest planet to our earth and also the brightest planet. It is also called morning and evening star because it looks brightest in the morning and evening from earth. On this planet there are present dense clouds of CO2.
3. EARTH: This is the planet we live on. Life is possible only on this planet.
Why life is possible on earth only?
The earth is organized into three layers- crust, mantle and core. The earth has its natural satellite called moon. The moon moves around the earth. About 71% of the earth's surface is covered by water. In addition to its revolution around sun it also rotates on its own axis and takes 24 hours to complete one rotation.
4. MARS: This is the fourth planet from the sun. It is also called red planet because it has a layer of red dust on it which is a chemical called iron oxide. This planet has a very thin atmosphere.
5. JUPITER: It is the biggest planet of our solar system. It can be observed from earth's surface. The gravitational force on this planet is the maximum.
6. SATURN: It possesses beautiful rings around it. These rings are made of dust, ice and rocks. It is the second largest planet of solar system.
7. URANUS: This planet also has rings but these are not visible.
8. NEPTUNE: It is the farthest planet from sun. This planet is faint and is not easily visible.
Terrestrial and Jovian planets: Some of the planets are put together in a category, and are given specific names.
Apart from sun and the planets, there are other heavenly bodies also in our solar system. Let us discuss them one by one;
Asteroids: These are minor planets and are also called planetoids. These are the objects which could not combine to form planets.
Comets: These revolve around the sun. They have a long tail. These are also called dirty snow ball because of ice and dust on them.
When they come towards the sun, due to solar heat the ice on comet evaporates and the comet whitens. When it happens, comet has a tail.
Meteors: Sometimes when we see a strike of light in the sky these are meteors. Several rocky objects revolve around the earth. When they enter into the gravitational pull of the earth, earth attracts them. When they enter into the atmosphere of earth, due to friction a lot of heat is produced and they start burning. This is when they appear in the sky as a streak of light for some time.
Galaxy: It is the collection of billions of stars, gases and dust held together due to gravitational pull. The galaxy we live in is called Milky Way.
Stars: These are the luminous bodies which possess the light of their own.
Constellation: Some stars make beautiful patterns or shapes in the sky. These shapes are called constellations.
Misconcept: The earth is the centre of the solar system.
Concept: Sun is the centre of the solar system and all the 8 planets revolve around it in their orbits.
Misconcept: The solar system contains only the sun, moon and planets.
Concept: Apart from the sun, moon and planets, the solar system also contains several stars, galaxies, asteroids, meteors, constellations, etc.
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