Planets of Solar system for Karnataka PC, KPTCL

While preparing for any exam, you need to be aware of general science. Basic knowledge of planets of solar system is required. In this blog you will know about the general information regarding the planet system. If you are preparing for PSI, KAS, KPTCL, KPC examinations Oliveboard has mock test packs for each exam and courses for PSI and KAS exam. You can visit our Karnataka Exam Section for more details.


According to Big Bang theory, which is presently a widely accepted theory about origin and evolution of the universe, estimates that the universe has emerged from a point-like particle which was very small in size(approx. few millimeter), extremely hot and infinitely dense and very similar to a supercharged black hole. About 13.8 billion years ago the tiny particle violently exploded as a bang and this bang created all the things that exist in this universe like matter, energy, space and time. After going through many stages of evolution for years, atomic particles, elements and so on were formed. These things became building blocks for everything that we see around us, things that we know and the things that exist in the universe right now.

In the time span of 13.8 billion years an uncountable number of galaxies were formed and got destroyed. It is estimated that, right now there are about 100-200 billions of galaxies. Among them, humankind knew only few. The galaxy in which our solar system exists is called the Milky Way and is spiral in shape. The nearest galaxy which is known to us is called Andromeda. The age of the Milky Way galaxy is not correctly estimated till the date. It is estimated that the Milky Way galaxy consists of about 100-400 billion stars and an equal number of planets.

Important points

  • Big bang theory is currently a widely accepted theory about the origin and evolution of our solar system.
  • According to the big bang theory, the universe started with a bang of extremely hot and infinitely dense small particles about 13.8 billion year ago.
  •  The Milky Way is the galaxy in which our solar system exists.
  • Andromeda is the nearest galaxy which is known to us.


Sun is a star among billions of other stars of the Milky Way galaxy with its own planetary system, which is called the Solar System. Solar system was formed around 4.6 billion years ago by the gravitational collapse of a giant interstellar molecular cloud. By virtue of its many interstellar things like planets, asteroids, stars, moons etc. were created. These started to revolve around the sun and around each other due to their gravitational forces. The Sun being the principal component of the solar system with most of the overall mass of the solar system is concentrated in it. Which comprise 98.6% of all the mass of the solar system (332,900 earth masses).

Sun has hydrogen and helium as its primary elements and because of its high temperature and density it enables nuclear fusion reaction of hydrogen into helium, which results in release of enormous amounts of energy, which radiates in the form of electromagnetic radiation peaking in the form of visible light. The sun continuously emits streams of protons in all directions known as solar wind, these interact with earth magnetic field and creates Aurora or northern lights. Sun also contains many elements in itself other than hydrogen and helium and it is thought that because of high metallicity of sun development of planetary system of sun was possible. Temperature of the sun is estimated to be 5,778k.Recently in 2021 NASA’s Parker solar probe became the first spacecraft to reach the outer atmosphere of the sun and now it is helping to understand more about the sun.

Important points 

  • Solar system was formed by the creation of the sun around 4.6 billion years ago when giant interstellar molecular clouds collapsed.
  • 98.6% of the mass of the solar system is concentrated in the sun.
  • Hydrogen and helium are primary elements of sun
  • The Sun also contains many other elements which enables the development of the planetary system of the sun.
  •  Because of the high density and temperature at the core of the sun, solar fission reactions happen in the sun.
  • High temperature of sun is radiated out in form of electromagnetic radiation(visible light)
  • Temperature of sun is about 5,778k
  • NASA’s Parker solar probe become first spacecraft to reach outer solar atmosphere

Important facts about planets 

  • Biggest planet – Jupiter
  • Smallest planet – Mercury
  • Biggest satellite – Ganymede
  • Smallest satellite – Deimos
  • Blue planet – Earth
  • Green planet – Uranus
  • Brightest planet – Venus
  • Brightest planet outside solar system – Sirius (dog star)
  • Closest star to solar system – Proxima Centauri
  • Coldest planet – Neptune
  • Evening star – Venus
  • Red planet – Mars
  • Slowest revolution in solar system – Neptune
  • Slowest rotation in solar system – Venus
  • Earth’s twin – Venus
  • Only satellite with atmosphere like earth – Titan

Planetary system of sun

The whole solar system consists of planets, moons, asteroids, dwarf planets etc, most of the planets and other interstellar objects in the solar system orbit(revolve) around the sun in the same direction as sun rotates around its axis, i.e. in counterclockwise direction. This rotation is called a prograde manner of rotation. Except some comets like Hailey’s comet and the moon of Neptune rotates in opposite directions. Presently in the solar system there are 8 planets in the solar system, 9 known dwarf planets, 796,354 known minor planets, 575 natural satellites of which 185 are planetary and 390 are minor planetary, 4,143 known comets. The 8 major planets of our solar system are Mercury, Venus, Earth, Mars, Jupiter, Neptune, Saturn, and Uranus. The 9 known dwarf planets are Ceres, Orcus, Pluto, Haumea, Quaoar, Makemake, Gonggong, Eris, Sedna.

The basis of 8 major planets of the whole solar system can be divided into two parts Inner solar system and outer solar system.

Inner solar system consists of four planets and an asteroid belt. The planets in the inner solar system are called inner planets. The planets in order of distance from the sun (closest to farthest) are Mercury, Venus, Earth and Mars. These planets are terrestrial planets, which means that they have a solid surface or land. This is because as they are nearer to the sun the sun’s gravity holds the heavy metals together. These planets have few moons or no moon and also they don’t have any ring system.

Outer solar system consists of very giant planets and their large moons, these planets are called Jovian planets. These are mostly gaseous planets; the four outer planets of the solar system are Jupiter, Saturn, Uranus and Neptune. 

Planets of inner solar system


Distance of mercury from the sun is 0.4AU or 60 million km. This is the closest planet to the sun and the smallest planet in the solar system. Its rotation period is 59 days and revolution period is 88 days(shortest year in solar system), as it is closer to the sun it is the fastest planet in the solar system and travels at the speed of 47 KM per second. It has a thin atmosphere or exosphere and consists of nitrogen, helium, potassium, sodium, hydrogen, oxygen. It doesn’t have any natural satellites. Despite being closer to the sun it is not the hottest planet of the solar system because of its thick atmosphere which does not allow the sun’s radiations to heat it up as compared to Venus. NASA’s Mariner 10 was first to fly by mercury and Messenger was first to orbit.


Distance of Venus from the sun is 0.7 AU or 1000 million Km. Venus is called as earth’s twin because of similar size and density but have radical differences between the two. Venus rotates very slowly on its axis. 1 day on Venus equals 243 earth days. But it orbits around the sun faster than earth one year on Venus equals 225 earth days. It is the brightest celestial planet after the sun. It has a thick atmosphere consisting of carbon dioxide, nitrogen and sulfuric acid gas because of thick sulfuric acid gasses greenhouse gasses are produced resulting in trapping heat from the sun and raising the temperature of the planet. Its temperature is around 400 degree celcius. The planet has no natural satellite. Unlike other planets it rotates from east to west in a clockwise direction. This planet was visited by the European space agency’s Venus express spacecraft.


Earth is the third nearest planet to the sun and only known planet to sustain life. Its distance from the sun is 1AU or 150 million km. It is the largest and densest planet among inner planets. It is the 5th largest planet in our solar system. Its size is similar to that of Venus (diameter 500 km more than Venus). Earth is called a blue planet because it has water and landmass which makes its appearance blue when viewed from space.

Area of earth is 510 million square km. The circumference at the pole is 40008 km and at the equator is 40075 km. According to radiometric dating, the earth’s age is about 4.45 billion years. Earth is covered with 71% water and 21% landmass. Earth rotates around the sun with the speed of 29.79 km/sec. It takes 365 days to revolve around the sun and 1 day to rotate around its axis. It has one natural satellite


Mars is the fourth nearest planet from the sun. Its distance from the sun is 1.5 AU 220 million km. It is also called a red planet because of the presence of iron oxide dust (rust) in its soil which makes it appear red. Mars has a thin atmosphere made up of carbon dioxide, argon, nitrogen, small amounts of oxygen and water vapors. One day on mars takes 24.6 hours and its revolution period is 687 days. It has two moons called Phobos and Demios many successful spacecraft have landed on mars, first one among them is Viking 1. India has also sent its spacecraft Mangalyan to mars.


Jupiter is the fifth nearest planet from the sun. Its distance from the sun is 5.2 AU or 780 million km. It is the largest planet in the solar system. It is also called the lord of heaven. It has a thick atmosphere mostly of hydrogen and helium, it has a solid core equal to the size of earth. Jupiter is the fastest spinning planet of our solar system with one rotation every 10 hours. Its revolution period is 12 years. A gigantic storm twice the size of earth has been raging in Jupiter for centuries and appears as a great red spot when viewed from earth. It has 80 known satellites and its satellite Ganymede is the biggest satellite of the solar system. NASA’s Juno satellite is the recent satellite which launched and visited Jupiter.


Saturn is the second largest planet in size. Its distance from the sun is 9.5 AU or 1.42 billion km. It is the second largest planet in the solar is the least dense of all planets. It is a planet which has 7 rings rotating around. The rings are mainly made up of ice blocks and rocks. It is a gas giant and its atmosphere consists mostly of hydrogen and helium gas. It has 82 stars and its star titan is bigger than Saturn itself. Titan has an atmosphere similar to earth. The revolution period of Saturn is 29 years and the rotation period is 10.3 hours. Saturn was visited by the Cassini spacecraft which was in a field close to the planet’s ring.


Uranus is the lightest of outer planets. Its distance from the sun is 19.2 AU 2.87 billion km. It was identified as a planet by William Herschel. Uranus has 13 known rings and has 27 known moons. Its atmosphere is made mainly of molecular hydrogen and atomic helium and small amounts of methane. Its surface is made up of a small rocky core of ice and most of its mass is dense fluid of icy materials like water, methane and ammonia. It takes 84 years to revolve around the sun and the rotation period is 10.8 years. It rotates from north to south and is inclined by 98 degrees from its axis. Voyager 2 is the only spacecraft that have visited Uranus


It is called a greenish star because of the presence of methane. Its distance from the sun is 30.1AU 4.50 billion km. It has 14 known natural satellites. Its atmosphere is made up of atomic helium, molecular hydrogen and methane. It was discovered by JG Galle of Berlin in 1846

It has a revolution period of 165 years and rotation period of 15.7 days. Uranus and Neptune together are called Jovian twins. NASA’s voyager 22 is the only spacecraft to visit Neptune. 


Q. Smallest planet of solar system is

A. Mercury is a smallest planet of our solar system

Q. Biggest planet of solar system is

A. Jupiter is a biggest planet of our solar system

Q. Which planet is known as Green Planet

A. Uranus is known as green planet

Q. Coldest Planet in solar system

A. Neptune is a coldest planet in solar system

Q. Closest star to solar system

A. Proxima Centauri is a closest star to our solar system


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