The Solar System

The Sun and bodies revolving around it, which includes 8 planets, satellites, comets, meteors and asteroids, together constitute the solar system. The source of energy for the sun is the nuclear fusion reaction in which Hydrogen changes into Helium.

The Sun

The part of the sun that we can see in known as photosphere. The outer most part of the sun, which is visible only at the time of a solar eclipse, is known as corona. A storm of hot atoms which dissipates from the photosphere of the Sun, overcomes its gravity and goes into the outer space, is known as Solar Flares. When Solar Flares reach the Earth's atmosphere, after colliding with the air and dust particles, it produces a spectacular colourful effect. In the North-Pole region, this effect can be seen as Aurora Borealis and in the South-Pole region as Aurora Australis. The regions from where the solar flares originate, some dark spots are seen, these are called Sun Sport. ISRO (Indian Space Reserch Organisation) is planning to launch a satellite called Aditya to study the sun. Time taken by the light to reach the earth form sun is 8 min 18 sec.

The Planets

These are the celestial bodies, originating from the sun and are revolving around it. They do not have their own light and receive light and heat from the Sun. All the planets revolve round the sun from west of east. But, Venus and Uranus are the exceptions, which revolve around the sun from east to west. 'Terrestrial Planet' are Mercury, Venus, Earth and Mars because of their structure being similar to that of the Earth. 'Jovian Planets' are Jupiter, Saturn, Uranus and Neptune bacause their structures are similar to the Jupiter.

• Mercury : This is nearest to the Sun and it is the smallest planet of the solar-system. It takes 8 8 days to complete one revolution of the sun. Life is not possible on this planet because of the absence of atmosphere. This member of the solar family has no natural satellite. Mariner-10 was the only artificial satellite.
• Venus : It is the Second closest planet to the Sun. This planet, unlike other planets, goes around the Sun from east to west and is the nearest planet to the Earth, it is the brightest object seen in the sky, after the Sun and the Moon therefore it is called 'Morning star' is well as 'Evening star'. Being almost similar to the Earth in size and mass it is also called the sister planet of the Earth. Its atmosphare is mainly composed of C02 (90-95%), which produces a 'Pressure cooker condition' on this planet. Venus also has no natural satellite.
• Earth : it rotates on its axis from west to east. It is tilted on its axis by 23%. It takes about 365% days to complete one revolution around the sun. Its average distance from the sun is about 150 million km. It looks blue when seen from the outer space due to the presence of large amount of water, hence it is also called the 'Blue Planet'.
• Mars : It is called 'Red Planet' bacuse of its red appearance. It is the only planet, besides earth, where the possibility of life exists, because of the presence of atmosphere and glacial water as observed by the artificial satellite, 'Mars Odyssey'. Its rotation is like that the earth. It has two natural staellites-Phobos and Domos, the smallest satellites of the solar system. The highest point on this planet is Nicks Olympia which is three times as high as Mt. Everest.
• Jupiter : This is the largest planet of the solar system. It has 28 natural satellites going around it wherein Ganymede is the largest satellite of the planet as well as of the solar system. Ayo, Europa, Calisto, Almethia, etc are other satellites. The atmosphere of the planet is composed of Hydrogen, Helium, Methane and Ammonia. It possesses the quahties of both a planet and a star, as it has its own radio energy. Its most distinguish feature is the great red spot, which is believed to be a complex storm in the atmosphere of the planet.
• Saturn : Its most spectacular and mysterious characteristic is the presence of fully developed rings around it. These rings are composed of Small particles, which go around this planet collectively, due to its gravitational force. It is also called the 'Gaseous Globe' Galaxy like Planet. It appears yellow in the sky. Like Jupiter, the atmosphere os Saturn is also composed of Hydrogen, Helium, Methane. 30 Natural satellites of this planet have been discovered, till date, of which Titan is the largest, having the size.comparale to Mercury and its Own atmosphere and the gravitational force. Other satellites of Saturn inclued Mimansa, Ensiladu, Tethys, Phobe etc. Saturn is the last planet of the solar system that can be seen through the naked eyes.
• Uranus : Due to higher inclination of axis, it is also known as 'Lying Planet'. Uranus reloves the sun from east to west. Its atmosphere is composed of Hydrogen, Helium and Methane. When seen through the telescope, it appears green. Being very far from the Sun, it is very cold. It has 5 rings around it like Saturn (having 7 rings). These Delta and Epsilon. This planet has 21 natural satellites. The Sun rises in its west and sets in its east.
• Neptune : It was discovered by a German astronomer, Johan Galle. Its atmosphere is very dense, consisting of Hydrogen, Helium and Methane. It appears light yellow in colour. It has 8 natural satellites, of which Tritan and Mereed are important.
• Pluto: It was discovered in 1930 by Clyde Tombagh and was considered as the ninth and the smallest planet of our solar system. But at the summit of International Astronomical Union (IAU) held in Prague (Czech Republic) on 24 August 2006, scientists withdrew the status of planet form it.

Satellites

These are the celestial bodies which revolve their respective planets and around the sun as well. Like planets, satellites also do not have their own light and shine with the light of sun. Like planets, their orbits are also elliptical.

Asteroids

These are found between the orbits of Mars and Jupiter. These are celestial bodies with sizes ranging from a few meters to hundreds of the kilometres of diameter, revolving around the sun. They have originated by the disintegration of the planets.

Planets according to their decreasing size:

1. Jupiter 2. Saturn 3. Uranus 4. Neptune 5. Earth 6. Venus 7. Mars 8. Mercury

Planets according to their decreasing mass:

1. Jupiter 2. Saturn 3. Neptune 4. Uranus 5. Earth 6. Venus 7. Mars 8. Mercury

Planets according to their decreasing density:

1. Earth 2. Mercury 3. Venus 4. Mars 5. Neptune 6. Jupiter 7. Uranus 8. Saturn

Terrestrial Planets:

1. Mercury 2. Venus 3. Earth 4. Mars

Jovian Planets:

1. Jupiter 2. Saturn 3. Uranus 4. Neptune

Planets according to decreasing revolution period:

1. Mercury 2. Venus 3. Earth 4. Mars 5. Jupiter 6. Saturn 7. Uranus 8. Neptune

Meteors and Meteorites

Meteors are the celestial bodies composed of dust and gases. After coming under the influence of earth's gravity, they move with a great velocity towards the earth. But, due to collision with the particles of the atmosphere they burn and get converted into ash. Meteors which are large in size and do not burn completely and reach the surface of the earth are called meteorites.

Coments

There are the bodies composed of dust, ice and gases, which come from the colder and darker areas, away from the sun. They go around the sun in large and irregular orbits. While moving in their orbits, when they come very close to the sun, they start glowing with a bright gaseous tail always pointing away from the sun. Many a times, comets are visible to the naked eye and present a very spectacular sight. Comet Halley, discovered by Edmund Halley, returns after every 76 years.