► The solar system consists of the sun, the eight planets and their satellites (or moons), and thousands of other smaller heavenly bodies such as asteroids, comets and meteors.
► The sun is at the centre of the solar system and all these bodies are revolving around it.
► The sun keeps all the planets and other objects revolving round it due to gravitational pull. Thus, the motion of all the members of the solar system is governed mainly by the gravitational force of the sun.
► Planets revolve around the sun in elliptical orbit.
►In the solar system the planet nearest to the sun is Mercury and the planet farthest from the sun is Neptune (not Pluto).
► The size of solar system has been estimated to at about 105 A.U.
► Mercury, Venus, Earth, Mars are called terrestrial planets and Jupiter Saturn, Uranus and Neptune are called gaseous planets.
► The sun is also the source of all the energy in the solar system.
► Pluto is a dwarf planet.
Members of the Solar System
The Sun
► The Sun is about 150 million kms away from the Earth.
► Light (at the speed of 300,000 km per second) takes about 8.5 minutes to reach the Earth from the Sun.
► Its diameter is 14lakh kms.
► The temperature at the centre is around 15,000,000° C.
► 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.
► 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.
► 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 Planets
► These are opaque bodies which continuously revolve around and are lighted by the Sun.
► There are eight planets in the Solar system.
► Jupiter is the biggest and mercury is the smallest planets of our solar system.
► 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 i.e. from big to small) is Jupiter > Satum > Uranus > Neptune > Earth > Venus > Mars > Mercury.
► A ninth planet has been recently discovered by NASA named as Carla.
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