The Sun
• The Sun is at the centre of the Solar System.• Its size is thirteen lakh times as that of the Earth.
• It is the nearest star to the Earth.
• It is an ultimate source of energy for life on Earth.
• Its diameter is 14 lakh kms.
• It is composed of 71%Hydrogen, 26.5% Helium and 2.5% other elements.
• Hydrogen and Helium are the main gases present in the Sun.
• Within the Sun, hydrogen is converted to Helium due to nuclear fusion releasing a tremendous amount of heat and light.
• It has a surface temperature of about 6000 C.
• The temperature at the centre is around 15,000,0000C.
• Shining surface of the sun is called photosphere, it appears like a disc
radiates energy and acts as a source of energy.
• The outer layer of sun's atmosphere made up of thin hot gases, is called Corona. Corona is visible only during a total eclipse of the sun (or with a special solar telescope called Coronagraph).
• The planet travels with the sun through millions of stars in our galaxy at a speed of about 70,000 km per hour.
• The sun is about 150 million kms away from the Earth.
• Light (at the speed of 3000000 km per second) takes about 8.5 minutes to reach the Earth from the Sun.
The Planets
• These are opaque bodies which continuously revolve around and are
• lighted by the Sun.
• There are eight planets in the Solar system.
• A ninth planet has been recently discovered by NASA named as
• Carla.
• The sequence of planets according to their distance from the Sun is
• Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune.
• The sequence of planets according to their size (in descending order ie. from big to small) is Jupiter, Saturn, Uranus, Neptune, Earth, Venus,
• Mars, Mercury.
• Jupiter is the biggest and mercury is the smallest planets of our solar system.
Classification of Planets
• The eight planets have been divided into two groups. All the planets of a particular group have some common features. Terrestrial planets or Rocky planets and' "Jovian planets' or 'Gaseous planets" (Gas giants) are the two groups of planets.
• The four planets nearest to the Sun-Mercury, Venus, Earth and Mars are called terrestrial planets, because their structure is similar to the earth.
• Other four planets-Jupiter, Saturn, Uranus and Neptune are called Jovian planets.
• Planets are classified into the following two groups inner and outer planets. These are separated by asteroid belt.:
Inner Planets
• They include Mercury, Venus, Earth, Mars.
• They are nearer to the sun.
• They are made up of dense metallic minerals.
• They move faster and have a shorter period of revolution
• They have thin, rocky crust.
• They have a mantle rich in iron and magnesium
• They have a core of molten metal’s.
• They have thin atmosphere.
• They have very few natural satellites (or moons)or no satellites.’’
Outer Planets
• They include Jupiter, Saturn, Uranus, Neptune etc.
• They are far away from the sun.
• They are made up of hot gases,mainely hydrogen and helium.
• They move rather slowly and have a longer period of revolution.
• They are all gaseous bodies.
• Made of gases.
• They have ring systems around them
• They have a large number of natural satellites or moons)
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