Competitive Examination Notes - 004

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Solar System - 01
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Solar system is a well structured unit consisting of a star the Sun around which 8 planets :- Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune orbited in order of increasing distance from the Sun. Around these planets revolve 168 known satellites and other yet to be discovered. Solar system contains another category of minor bodies which can be divided into Asteroids, thousands of minor bodies orbiting Sun in between Mars and Jupiter, the Comets, the ring system of Jupiter, Saturn and Uranus and interplanetary dust.

A good model of the solar system is a flat disk which Sun at its center and a succession of nearly concentric circles in a plane of the disk representing orbits of planets. Orbit of mercury is inclined to the plane of the disk. Planetary orbits are well separated from each other. Moreover, the separation increases approximately in geometric progression with distance from Sun. Distances in solar system are expressed in Astronomical Unit, defined as the mean distance between Earth and the Sun about 14.9 million kilometers.

Greater part of the mass of the solar system is concentrated in Sun. This has a mass of 1.9X10^-33 and represents 99.86% of the whole. Among the planets Jupiter is the most massive (318 Earth), followed by Saturn with 95 Earth mass.Because of differences in mass, size and composition, planets fall into two distinct groups.

The Inner Planets are Mercury, Venus, Earth and Mars. Jupiter, Saturn, Uranus and Neptune comprise the Outer Planet.

Known as terrestrial planets, the inner planets are essentially rocky bodies. Among the group Earth is the largest with a radius of 6,378 Km, followed by Venus 6,050 Km, Mars 3,398 Km and Mercury 243 Km. Mercury, Venus, Earth are the densest bodies in the solar system.

Next  :- Solar System - 2