Solar System

Category : 4th Class


This lesson will help you to:

  • learn about the solar system.
  • study about different planets and their moons.
  • learn about stars.
  • learn about asteroids.
  • learn about the movement of planets in the


Real Life Example

  • In the night if we see the sky closely, we can see several shooting stars. These shooting stars are actually meteors that are burning



Solar System: The sun, its planets and all the objects moving around them collectively are called solar system. The solar system is in a galaxy known as "the milky way". About 99.86 percent of the mass of the solar system is made up of the sun. There are 8 planets in the solar system.




  • Sun is a ball of hot, burning gases. It is made of gases called hydrogen and helium.
  • Sun is the nearest star to the earth.
  • Sun is the source of all energy for life on earth.
  • The outside of the sun is 11,000 degrees Fahrenheit.
  • On the sun's surface, there are dark patches known? as sunspots. These are patches of gas that looks, dark since they are cooler than their surroundings.



  • Planets are heavenly bodies, which revolve around the sun in elliptical orbits.
  • All planets fall in 2 groups Inner Planets: Mercury,: Venus, Mars and Earth are called inner planets. Outer Planets: These are Jupiter, Saturn, Uranus and Neptune,                                
  • Between Inner &. Outer planets, there is a ring of small bodies, which are made of rock & metal, these are called Asteroids. They also keep moving around the sun. This ring is also called Asteroids belt.
  • The inner planets are also called the rocky planets, because they are made of rocks.


Amazing Facts

  • A person of 60 kg weight barely will weigh 10 kg on moon. That means, you would weigh 1/6th of your weight on moon. This happens due to gravitational pull at different places.
  • It takes about 1.25 seconds for moonlight to reach the earth whereas sunlight reaches earth in 8 minutes 19 seconds, so you can judge how close moon is to us & how far sun is from earth.
  • In space, astronauts cannot cry, because there is no gravity, so the tears can’t flow.
  • Saturn has such a low density that it would float if put in water.



  • Mercury has large variations in temperatures during day and night.
  • Mercury does not have any satellite.
  • There is no water or atmosphere on Mercury.
  • Mercury can be seen with naked eyes.
  • A year at Mercury is of 88 days as it takes Mercury 88 days to orbit the sun, so Mercury has shortest year among all planets.
  • There are no seasons on Mercury's surface.



  • Venus orbits the sun once in about 225 earth days.
  • Venus has no oceans. Its atmosphere is made mostly of carbon dioxide. There is almost no water vapour in its air. Venus is totally covered by clouds, this is why it is also called Veiled planet.
  • There are also many volcanoes on Venus. The volcanoes are not active anymore, which means they do not erupt.
  • Venus is covered by thick clouds, so it reflects lot of sunlight making it brightest planet. Also it is the hottest planet of solar system.
  • Venus reaches its maximum brightness shortly before sunrise or shortly after sunset, so it is also known as the Morning star or Evening star.
  • It has the slowest rotation in the solar system.


Historical preview

  • For many thousands of years, humanity, with a few notable exceptions, did not recognize the existence of the solar system. The invention of telescope has led to the discovery of further planets and moons. In more recent times, improvements in the telescope and the use of unmanned spacecraft have enabled spacecraft have enabled the investigation of various geological phenomena.
  • Origin of some celestial words: planet word comes from Greek word planasthai; which means to wander, satellite word comes from Latin word stateless, which means attendant, solar also comes from a Latin word solar also comes from a Latin word solaris meaning sun.
  • There were nine planets, until Pluto was downgraded to dwarf planet status in 2006.



  • It is the largest of the four inner planets.
  • Earth is often called the "Water Planet" because it is the only planet in our solar system which has liquid water on its surface. About 71% of the surface of earth is covered by water. The other part of earth is made up of continents and islands which have different landforms on them.
  • It reflects about 1/3rd of sunlight it receives.
  • Earth is called the blue planet. From space the oceans combined with the atmosphere makes the planet look blue.
  • Due to gravity, the layer of gases remains attached to it (which is known as atmosphere), it prevents too much heat or UV rays from sun reaching the earth.
  • Moon is the only satellite of the earth.
  • It revolves around the sun, due to its tilt, seasons are created.
  • It rotates about its own axis, thus creating day night. It takes 24 hours to do that.
  • It orbits the sun once in about 365 earth days.



  • Mars has approximately half the diameter of earth.
  • It has two satellites.
  • Mars is named after the Roman god of war.
  • It is also called the red planet.
  • Mars also has the largest dust storms in the solar system.




  • It is named after the Roman god Jupiter (ruler of Roman gods)
  • Jupiter is the largest planet within the solar system.
  • Jupiter is so big that you could fit all the other planets in the solar system inside it.
  • It has a great red spot, it is rotating storm system inside the planet.
  • Jupiter rotates faster than any other planet.
  • It completes one rotation in 10 hours.
  • Jupiter has a faint ring system; these rings appear to be made of dust.
  • This is also a windy planet as the fast rotation causes high winds.



Misconcept: The earth is the center of the solar system.

Concept: Sun is the center 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, constellation etc.


An Interesting Shortcut to Remember Plants

  • If you are having problems remembering the planets in their correct order, just remember this sentence “My very Educated Mother Just Served Us Naan,” Mercury, Venus, Earth Mars, Jupiter, Saturn, Uranus, Neptune.



  • Saturn is the sixth planet from the sun and the second largest planet in the solar system, after Jupiter.
  • It is named after the Roman god Saturn.
  • Saturn is classified as a gas giant planet.
  • It has 22 known satellites.
  • Saturn's rings are made of many pieces of rocks &. ice.
  • Saturn has the greatest number of known moons of any planet in the solar system.



  • Uranus appears to lie on its side
  • It is named after the Roman god of the sky.
  • The only planet, which rotates on its axis from east to west.
  • It has 27 known satellites.
  • It has at least ten thin uniform black rings, which are made of dust.
  • It is a very cold planet; it receives 370 times less sunlight than earth as it is far away from sun as compared to earth.
  • Uranus is tilted in such a way that a season lasts there for 20 years.



  • As it is very far from sun, it completes an orbit on average every 164.79 years.
  • The average distance between Neptune and the sun is 4.50 billion km.
  • Neptune is known to be the coldest planet in solar system, also it has slowest revolution speed in solar system.
  • Can't be seen with naked eye.



  • It is the earth's only satellite.
  • Like everything else in solar system, moon also does not have its own light. It shines due to sun's light.
  • There is no water on its surface.
  • The moon has no atmosphere, so there is huge difference between day & night temperature.
  • It's diameter is l/4th of the earth.
  • It looks bigger to us as it is very close to us.



  • A meteoroid is a small rock or particle of debris in our solar system. They range in size from dust to around 10 metres in diameter.
  • A meteoroid that burns up as it passes through the earth's atmosphere is known as a meteor. If you've ever looked up at the sky at night and seen a streak of light or 'shooting star' what you are actually seeing is a meteor.
  • A meteoroid that survives falling through the earth's atmosphere and colliding with the earth's surface is known as a meteorite.





A star is a gigantic, glowing ball of plasma.

Stars are first formed as clouds of dust and gas.

Stars give off a tremendous amount of energy in the form of light and heat.

The star that is closest to the earth is the sun.


Galaxy is a collection of stars, gas, and dust bound together by gravity. The smallest galaxies may contain only a few hundred thousand stars, while the largest galaxies have thousands of billions of stars. The Milky Way galaxy contains our solar system.




A constellation is a group of stars, which seem to be forming different figures, letters, etc. at night.

This term has come from the latin words con, which means together and Stella, which means star.

Example: Ursa Minor, Ursa Major etc.



  • An asteroid is a large rock in outer space. Some, like ceres, can be very large, while others are as small as a grain of sand.
  • 26 very large asteroids have been discovered, which are mostly the big ones. But there are still millions of smaller ones that we are yet to see because they are too tiny,



A celestial body moving about the sun, consisting of a central mass surrounded by an envelope of dust and gas that may form a tail that streams away from the sun. When close enough to the sun they display a visible coma (a fuzzy outline or atmosphere due to solar radiation) and sometimes a tail.

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