The solar system is a group of sun, eight planets, their satellites, comets, asteroids and meteors. The sun is at the center of which moves through the space taking its family members. All the planets revolve around the sun in elliptical path sue to its gravitational force. The sun is spherical, medium sized star around which the earth and other planet revolve. Some data about the sun are:

Surface of temperature	6000⁰ C
Core temperature	1.5×107⁰C
Diameter	1382400 Km
Composition	Hydrogen(74%), Helium(25%) and other
Distance from earth	1.5×108m

Production of energy from the sun: The sun is extremely hot and rich in hydrogen. It produces energy continuously in the form of heat and light. It is due to the nuclear fusion occurring in it. In this reaction, the hydrogen atoms fuse to form helium atom. During the reaction sufficient amount of energy is released. The sun consists of electrically charged gases ions which are called plasma. The flowing of electrically charged particles or ions on the outer surface of the sun is called solar wind. The velocity so solar wind is about 500km/s.

Importance of Sun

• It provides necessary heat and light. Therefore life is possible on the earth.
• It provides light for shining the planets as they have no light of their own.
• Solar battery converts solar energy into electrical energy which is used to operate artificial satellites, heaters, vehicles etc.
• It provides necessary centripetal force for planets to revolve around it.

Planets

The members of the solar system that revolve around the sun in closed elliptical orbit are called planets. They do not have their own light. They shine only due to the reflection of light from the sunlight. All planets of the solar system rotate on their own axis and at the same time they revolve around the sun in their own orbit. The time taken by the planets to rotate about its own axis is called planet’s day and the time taken by the planets to revolve once around the sun is called planets’ year. There are 8 planets in our solar system which are divided into outer and inner planets.

Inner planets: The planets which are found inside the belt of asteroids are called inner planets. They are mercury, Venus, earth and mars.

Outer planets: The outer planets (sometimes called Jovian planets or gas giants) are huge planets swaddled in gas. They all have rings and all of plenty of moons each. Despite their size, only two of them are visible without telescopes: Jupiter and Saturn. Uranus and Neptune were the first planets discovered since antiquity, and showed astronomers the solar system was bigger than previously thought.

Mercury ( Budha)

• It is the closet planet to the sun and has shortest periods revolution.
• It is the smallest planet in our solar system.
• It completes one revolution in 88 days and one rotation in 59 days.
• It has no atmosphere.
• There is a vast difference in daily temperature. During day the temperature reaches to about 427⁰C and night to -173⁰C.
• It has no satellite.

Venus (Sukra)

• Its size is almost the same as that of the earth.
• It s the brightest planet among the planets and so called the evening or morning star.
• It completes one rotation in 225 days and one revolution in 243 days.
• It has atmosphere which consists of carbon dioxide and thick cloud of sulphuric acid. So it is hottest planet. Its surface temperature is about 482⁰C.
• It has no satellite.

Earth (Prithvi)

• The earth is only planet where the life is possible.
• It completes one rotation in 24 hours and one revolution in about 365 days.
• Its atmosphere consists of O₂, CO₂, N₂, water vapor etc.
• It has only one satellite called the moon.

Mars (Mangal)

• It is reddish in color due to the presence of red colored minerals called limonite.
• It completes one rotation in 24 hours and 37minutes and one revolution in 687 days.
• Its surface is volcanic in nature. The highest volcano on its surface is two times more in height than Mt. Everest.
• It is covered with dark patches called seas of mars although there is no water.
• Its atmosphere is thin and consists of nitrogen, carbon dioxide, inert gases and oxygen (not enough to support life.)
• It has polar caps. It has been believed that it is seen due to the frozen ice of gases.
• Its surface temperature varies from -50⁰C to 40⁰C.
• It has two satellites Phobos and Deimos.

Jupiter (Brishpati)

• It is the largest planet. It is always covered with layers of dense cloud.
• It completes one rotation in 9 hrs 55 minutes and one revolution in 12 years.
• A red spot is seen on its surface which is due to the hurricane. It is larger than the earth.
• Its atmosphere consists of methane, helium, ammonia etc.
• Its surface temperature is about -143⁰C.
• It has 17 satellites. Europa, Io, Calisto, Ganymede etc. are some satellites.

Saturn (Shani)

• It is the second largest planet.
• It is unique among the planets and can be distinguished by its prominent rings. The rings consist of ice pieces and dust particles.
• It completes one rotation in 10 hrs. and 14 min and one revolution in 29 years.
• Its atmosphere consists of methane, ammonia, hydrogen and helium.
• Its average surface temperature is about -180⁰C.
• It has 22 satellites. Titan is the biggest satellite.

Uranus ( Arun)

• It is the giant ball of gas and liquid.
• It completes one rotation in 17hrs 14min and one revolution in 84 years.
• Its atmosphere consists of hydrogen and methane. I appear greenish in color due to the high proportion of methane in its atmosphere.
• Its average surface temperature is -200⁰C.
• It has strong magnetic field.
• It has 15 satellites. Some of them are Miranda, Arial, Umbrial, Oberon etc.

 

Neptune ( Barun)

• It is the third largest planet.
• It completes one rotation in 10 hrs and one revolution in 164 years.
• Its atmosphere consists of hydrogen, helium and methane.
• In this planet, a great spot is found which is about the size of the earth.
• Its surface temperature is about -2180⁰C.
• It has 8 satellites. Triton I the largest satellite.

• The solar system is a group of sun, eight planets, their satellites, comets, asteroids and meteors. The sun is at the center of which moves through the space taking its family members.
• The members of the solar system that revolve around the sun in closed elliptical orbit are called planets.
• The velocity so solar wind is about 500km/s.
• Inner planets: The planets which are found inside the belt of asteroids are called inner planets. They are mercury, Venus, earth and mars.
• Outer planets: The outer planets (sometimes called Jovian planets or gas giants) are huge planets swaddled in gas. They all have rings and all of plenty of moons each.