The Solar System is a group of different objects which are bounded by gravitational force. The Solar system consists of the Sun, eight planet and their satellites and other small bodies such as Astroid, Comets and Meteors.

In this article, we discuss important facts about Solar System which asked gk section in various exams.

Composition of Solar System

The solar system consists of the Sun, Eight planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune), Dwarf planets, and a number of other smaller bodies such as asteroids, comets, and meteoroids.

  • The size of the solar system is about 105 A.U.
  • Almost 99.9% of the solar system is dominated by the Sun.
  • The Sun is the only source of energy in the solar system. It is the powerhouse of our Solar System.
  • The sun is the centre of our solar system and all other bodies are revolving around it in their particular orbit.
  • The solar system is based on the Heliocentrism model (The sun is at the centre) not on the Geocentric model (The Earth is at the centre).
The Solar System

Members of the Solar System

All the objects which are bound by the gravitational force and lead to the formation of the solar system are members of the solar system. let us discuss some important facts about these.


  • The Sun is a star and it is the nearest star to the Earth.
  • It is at the centre of the Solar System.
  • The source of energy of the sun is nuclear fusion.
  • The Sun is about 150 million km away from the Earth. It takes around 8 minutes and 30 seconds for light at the speed of 3 lakh Km/sec to reach the earth.
  • Temperature:-
    • The temperature at the surface is 6000K = 5600oC = 10800oF.
    • The temperature at the centre is 15.7 million K
  • Size:-
    • It is huge in size It comprises 99.9% of the mass of the solar system.
    • The diameter of the Sun is 1392000 km.
    • The density of the Sun is 1/4 of the density of the Earth.
    • Its size is 13 lakh times that of Earth.
  • Composition:-
    • It is composed of extremely hot gases.
    • Hydrogen (71%), Helium (26.5%) and 2.5% other elements.
  • Photosphere:- The Shining surface of the Sun is called the photosphere.
  • Corona:- The outer layer of the Sun’s atmosphere which is made up of thin hot gases is called Corona.
  • Nuclear Fusion:– The process in which small nuclei of hydrogen atoms fuse into a helium atom called nuclear fusion.

What are Solar Flares?

A storm of hot atoms which dissipates from the photosphere of the Sun to overcome its gravity and goes into outer space is known as a solar flare. When solar flares reach the earth’s atmosphere after colliding with the air and dust particles it produces a spectacular colourful effect it is known as Aurora.

What is Sun Spot?

In the region from where the solar flares originate some dark spots are seen these are called Sun Spots.

  • The sunspots are colder regions of the sun has a temperature of about 1500oC.
  • Sunspots appear and disappear after every 11 years which is called Sun Spot Cycle.
  • Sun Spots produce strong magnetic fields which hamper the wireless communication system of the Earth.

What are Solar Winds?

The Sun is continuously emitting streams of protons in all directions either as spiral streams called Solar Winds or bouts of incandescent material called Solar Flares.


In 2006, the International Astronomical Union (IAU) adopted a new definition of a planet it states that a planet is defined as a celestial body that:

  • Is in an orbit around the Sun.
  • Has sufficient mass so that it assumes a hydrostatic equilibrium shape.
  • Has “cleared the neighbourhood” around its orbit.

In our solar system, there are 8 planets. These planets revolve around the Sun in an elliptical orbit.

  • The sequence of planets according to their distance from the Sun in ascending order from the sun is Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
  • The sequence of planets according to their size from bigger to smaller is:- Jupiter > Saturn > Uranus > Neptune > Earth > Venus > Mars > Mercury

Based on their position the planets are classified into two groups inner planets and outer planets. These are separated by an asteroid belt.

Inner PlanetsOuter Planets
1. They are Mercury, Venus, Earth and Mars.1. These are Jupiter, Saturn, Uranus, and Neptune.
2. They are made up of dense metallic minerals.2. They are made up of hot gases.
3. They move faster3. They move slower

Formation of Planets

Planets were formed at least 4.6 billion years ago when gravity caused discs of dust and gas orbiting the sun to collapse and clump together. This disc, known as the solar nebula, was primarily made up of hydrogen and helium, with minor amounts of other elements.

On the bases of the formation of the planets, these are categorised into two groups:

  1. Terrestrial or Rocky Planets: These are made up of solid rocks and metal. Mercury, Venus, Earth, and Mars are rocky planets.
  2. Jovian or Gaseous Planets: These are made up of gases like hydrogen, helium, and methane. Jupiter, Saturn, Uranus, and Neptune are jovian planets.

Dwarf Planet:- A “dwarf planet” is a celestial body that:

  • Is in orbit around the Sun,
  • Has sufficient mass for itself-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape.
  • Has not cleared the neighbourhood around its orbit, and
  • Is not a satellite.


  • As per the new definition of Planets determined by the International Astronomical Union (IAU), Pluto has been omitted from the list of planets in 2006.
  • Pluto is considered a dwarf planet (size between planets and asteroids) now and it is a member of the Kuiper Belt.

Kuiper Belt is a spherical boundary outside the orbit of Neptune containing a number of asteroids, rocks, and comets.


Asteroids are rocky and metallic objects that revolve around the Sun in an orbit but they aren’t large enough to be termed planets.

  • They are called Minor Planets.
  • Most of them are found between Mars and Jupiter’s orbits.
  • Ceres is the largest Asteroid.

Meteors and Meteorites

Meteors are small-sized rocky material which is generally formed due to asteroid collision and approaching the earth.

  • These are also known as Shooting stars.
  • Meteors are usually small and due to heat produced by the air resistance in Earth’s atmosphere, they burn before reaching the Earth’s surface.
  • Meteorites:- These are meteors which do not burn completely and land on Earth’s surface.
  • Willamette, Mbozi, Cape York, and El Chaco are some meteorites found on Earth.
  • Lonar lake, Maharashtra in India is supposed to be created by a meteor impact in Pleistocene Epoch.


Comet is derived from the Latin word Stella Cometa which means ‘Hairy Star’. These are rocky and metallic materials surrounded by frozen gases.

  • These are shiny, luminous “Tailed Stars”.
  • These are generally found in Kuiper Belt.
  • They travel towards the Sun. while travelling their tail faces opposite of the sun and their head faces towards the Sun.
  • They become visible when they travel close to the Sun.
  • When the Comet travels close to the sun the ice melts into a head of gas called a Coma
  • Halley comet is famous that appeared last time in 1986 and reappears after every 76 years.

Important Facts About Planets

1. Mercury:-

  • It is the Smallest planet with a diameter of 4900 Km.
  • It is the Fastest Planet with a speed of 172500 Km per hour to complete a revolution around Sun in 88 days.
  • It has a magnetic field.
  • The planet with no water and gases like Nitrogen, Hydrogen, Oxygen and Carbon Dioxide.

2. Venus:-

  • It is the nearest planet to the Earth.
  • Venus is the brightest planet because it reflects most of the Sun’s light which falls upon it.
  • Venus is similar to the Earth in volume, weight, and density; therefore, it is called the sister of the Earth (Earth’s twin).
  • It is also known as Evening Star and Morning Star. It can be seen in the morning and evening with open eyes.
  • Venus is the hottest planet in the Solar system because of 96% CO2.
  • It has the slowest rotation period (243 days).
  • It rotates around the axis in a clockwise direction like Uranus.

3. Earth:-

  • The only Planet to give support to live with a pleasant atmosphere.
  • Earth is the fifth-largest planet.
  • It is tilted at 23½ degrees on its axis and thus makes an angle of 66½ degrees.
  • It takes 23 hours, 56 minutes, and 4 seconds to rotate on its axis with a speed of 1610 km/h.
  • It rotates in an anticlockwise direction which is from West to East.
  • The earth’s spin axis is tilted concerning its orbital plane which leads to the occurrence of the seasons.
  • It takes 365 days, 5 hours, 48 minutes, and 46 seconds (i.e. approx. 365½ days) to revolve around the Sun.
  • The rotation creates days and nights.
  • Also known as “Blue Planet” because of the presence of water on it.
  • It has only one satellite — the moon.

4. Mars:-

  • It is known as the “Red Planet” because of Iron-rich red soil.
  • It has two natural moons “Phobos” and “Deimos
  • It has a thin atmosphere comprising carbon dioxide, nitrogen, and argon.
  • Space missions that have been sent to Mars are Vikings, Pathfinder, Mars Odyssey, and Curiosity.
  • Olympus Mons” – Largest volcano and the tallest mountain in the solar system lies on Mars.

5. Jupiter:-

  • It is the largest planet in the solar system.
  • Jupiter is called the Lord of Heaven.
  • It is also known as the winter planet.
  • One special feature is the ‘Great Red Spot’.
  • The Ganymede satellite of Jupiter is the largest satellite in the solar system.

6. Saturn:-

  • Saturn is the Second largest planet.
  • It has bright and concentric rings around it which are made up of tiny rocks and pieces of Ice.
  • It has 82 moons and Titan is the largest among them.

7. Uranus:-

  • It is Greenish in colour.
  • It is Discovered by William Herschel in 1781.
  • Uranus is also known as the “Ice Giant”.
  • It has the coldest planetary atmosphere in the solar system.
  • Rotates clockwise on its axis like Venus.
  • Famous moons are Miranda, Ariel and Umbriel
  • The axis of Uranus has a large inclination so that it appears to be lying down; hence it bears the name “a planet on its side”.

8. Neptune:-

  • The farthest planet from the Sun.
  • It was discovered by Johann Galle and Urbain Le Verrier in 1846. The only planet in the solar system found by Mathematical Predictions.
  • It is also “Ice Giant”. The atmosphere is primarily composed of Hydrogen and Helium.
  • It has 14 satellites. Famous moon – Triton.
Solar System Notes

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