The Solar System, Sun, Planet, and Satellite

The sun and the planets which revolve around it along with their respective satellites and asteroids form the solar system.

Planet of Our Solar System 

  • The eight planets of the solar system can be divided into two groups:
    • Inner planets
      1. Mercury Venus Earth and Mars are the inner planets
      2. inner planets are also known as terrestrial planets as they are Rocky and dense
    • Outer planets 
      1. Jupiter Saturn Uranus and Neptune are the outer planets
      2. outer planets are large with no solid surface.
      3. It is believed that they have a small solid core and rotate relatively fast around their axis.
The Solar System, Sun, Planet, and Satellite image
Image: The Solar System, Sun, Planet, and Satellite
  • All planets of our solar system revolve in Elliptical order around the sun.
  • Many planets of the solar system have satellites that revolve around them.
  • Moon is the only satellite of The Earth.
  • Jupiter has more than 63 satellites
  • Saturn has more than fifty-six satellites.
  • How many planets have rings? Four Planets of our solar system have rings. All four are giant gas planets – Jupiter, Saturn (Largest ring system), Uranus, and Neptune.
  • Ceres is the largest asteroid in our solar system.

 We will begin our journey with a trip to the sun which is a star and is at the center of the solar system.

The Sun

  • The Sun’s diameter is about One million three hundred ninety-two thousand kilometers.
  • 3/4 of the Sun’s mass is hydrogen and almost 1/4 of its mass is helium.
  • The Sun also has some amounts of oxygen, carbon, and neon.
  • The sun is no different from all the other stars we see in the sky.
  • Similar to other stars, the sun is a ball of burning gases and generates its own light and heat.
  • The sun generates energy by a process called nuclear fusion. It turns large amounts of hydrogen into helium every second creating heat and light in the process. That is why the sun is very hot.
  • It is around 6,000 degrees Celsius hot at the surface.
  • Why Sun appears as the biggest star?– Among thousands of stars in the universe the Sun appears the biggest because it is the nearest star to the Earth.
  • It is at a distance of about 149.6 mn Kilometers
  • Light reaches the Earth from the Sun in about 8.19 minutes.
  • The energy of the Sun’s light and heat support all life on the Earth.
  • All the planets and astronomical objects in the solar system are bound to the Sun by gravity.
  • All planets of the solar system revolve around the Sun in a fixed orbit.

The Earth

  • The Earth takes about 365 days and 6 hours and 8 minutes to complete one revolution around the Sun.
  • What causes seasons on Earth?- The Earth’s axis is always inclined in the same direction at an angle of 23.5 degrees to the vertical. This inclination of the Earth’s axis together with the Earth’s revolution around the Sun causes seasons.
  • The sun’s size is about 109 times that of the earth. It is almost 99.86 percent of the total mass of the solar system.


  • Mercury is the closest planet to the Sun- about 36 million miles away from the sun.
  • Mercury is the smallest planet in our solar system.
  • Its diameter is just less than half the diameter of the Earth.
  • Mercury completes one revolution around the Sun in only 88 days
  • Mercury takes 58 days to complete one rotation on its axis
  • During the day – Mercury’s temperature goes above 400 degrees Celsius due to its proximity to the Sun at night.
  • The temperature drops down to minus 175 degrees Celsius as mercury loses all its heat because it has almost no atmosphere to trap Sun’s Heat.


  • It is the second nearest planet to the Sun.
  • Which planest is known as the morning star and why?– Venus is known as the morning star or evening star as it can be seen clearly from the earth just before sunrise and sunset.
  • Venus which is almost the same size as the earth completes one revolution around the Sun in 225 days.
  • Venus rotates at lower speed than Mercury.
  • It takes about 243 days to complete one rotation on its axis.
  • Venus has a very thick layer of atmosphere which is made of carbon dioxide, nitrogen and some other poisonous gases.
  • The layer of the atmosphere maintains high pressure on the planet and traps the sun’s Heat.
  • Why did venus consider the Earth’s twin? – Venus is considered as ‘Earth’s twin’ because of their close proximity in size, mass, and density with Earth.

What is Natural satellite?

  • A natural satellite is a Celestial body that orbits a planet or smaller body.
  • The Moon is the Earth’s natural satellite.
  • Mercury and Venus have no satellites.
  • Mars has two small satellites.
  • The larger outer planets have many satellites.

What is Artificial satellites?

  • An artificial satellite is an object that people have made and launched into orbit using rockets.
  • They are sent into space for various purposes such as sending television signals and monitoring weather conditions.
  • The first artificial satellite Sputnik 1 was sent by the Soviet Union in 1957 since then thousands of satellites have been launched into space.


  • It is the third planet of the solar system.
  • It is known to the only planet that supports life.
  • The Earth is nearly 13,000 kilometers wide.
  • It is the only planet in the solar system with water on its surface.
  • Two-thirds of the planet is covered by water.
  • The presence of water on it makes it ideal for life to sustain.


  • The Moon is about one-third the size of the Earth.
  • It has no light of its own and reflects the light of the Sun.
  • It does not have any atmosphere.
  • It also doesn’t have any liquid water on its surface.
  • During the day, it becomes very hot, but at night it is icy cold.
  • It revolves around the earth.
  • It completes one rotation on its axis in 27 days and 8 hours. This is why only one side of the moon is visible from the earth.
  • The visible side of the Moon is called the near side.


  • Mars is only 7,000 kilometers wide, which is a little over half the width of the earth.
  • It has a thin atmosphere.
  • The surface of Mars is very dry and Dusty like a desert on the earth.
  • It is also very cold.
  • There are a lot of loose rock sand dunes of fine sand on it.
  • It has the highest mountain in the solar system i.e. The shield volcano, Olympus Mons (Mount Olympus).
  • One revolution of mars around the Sun takes 687 days.
  • It has two satellites Phobos and Deimos. They are small and irregularly shaped.

We have completed our tour of the inner planets and now it is time to move towards the outer planets.

Asteroids or planetoids

  • Thousands of irregular small celestial bodies revolve around the sun between the orbits of Mars and Jupiter. They are called asteroids or planetoids.
  • It is believed that they are fragments of planets that existed between the orbits of Mars and Jupiter.

Now that we have dodged the asteroids. Let’s visit Jupiter.


  • Which is the largest planet of our solar system?– Jupiter.
  • It is also known as the gas giant because most of the planet is made up of liquid and gas.
  • Jupiter is a cloudy windy and Stormy Planet.
  • It is always covered by a layer of clouds.
  • It completes one revolution in almost 12 years.
  • Jupiter has 63 known satellites.
  • Which is the largest satellite in the solar system? Jupiter’s satellite Ganymede is the largest satellite in our solar system and the only moon with its own magnetic field.


  • The planet Saturn is the planet with a ring around it.
  • It has three rings around it made up of rock and ice particles. These particles range in size from tiny specks of dust to the size of a house. Some particles can even be as large as a few kilometers wide.
  • The second-largest planet of the solar system is Saturn
  • It consists mostly of gas and liquid though it may have a small core of rock and ice.
  • Like Jupiter, even Saturn has many satellites.
  • Scientists have so far identified 56 satellites.
  • Saturn’s biggest satellite Titan is almost as big as some planets.
  • It takes 29 years to complete one revolution around the Sun.


  • Uranus has 11 Rings.
  • They are dark in color and very hard to see.
  • Unlike other planets, Uranus orbits around the sun in a clockwise direction from east to west.
  • Uranus consists mostly of rock and ice.
  • Uranus also has 27 known satellites.
  • It takes 84 years to revolve once around the Sun.


  • Neptune is the farthest planet of the solar system.
  • Its diameter is almost four times that of the Earth.
  • It consists mainly of rock and metal in the core.
  • The core is surrounded by rock, water, ammonia, and methane.
  • The atmosphere of Neptune is made of hydrogen, helium, and methane.
  • Why is Neptune blue?– Neptune appears blue-green because of the presence of Methane in its atmosphere.
  • It takes 165 years to complete one revolution around the Sun.
  • Neptune has 13 satellites.

What is Dwarf Planet?

According to International Astronomical Union (IAU), there are four criteria for a celestial body to be considered as Dwarf planet:

  1. The body orbits around the sun.
  2. The body is not a moon.
  3. The body has not cleared the neighborhood around its orbit.
  4. The body has enough mass for its gravity to pull it into a rough shape.

What is Ocean World?

  • Ocean world is an astronomical body possessing a significant amount of water.
  • Recently, Ceres (lies in asteroid belt between Mars and Jupiter) given the status of an ‘Ocean World’.

What is the difference between Meteorides and Meteorites?

Meteorides is any small piece of debris or rock which moves around the sun.Meteorites is any solid piece of debris from an object, such as comets, asteroid, or meteoroid, that originates in outer space and survives it passage through the atmosphere to reach the surface of a planet or moon

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