Friday, 18 March 2011

Universe and Solar System

Universe and Solar System

In the vastness of the Universe, the Earth, the Sun and planets are tiny dots. The Sun is a single star in a Galaxy comprising 100,000 million stars.

The Solar System is centred on the Sun. It consists of a star called the Sun and all the objects that travel around it. The Solar System includes : 9 planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto), along with the numerous satellites that travel around most of them; planet-like objects called asteroids (hundreds of asteroids); chunks of iron and stone called meteoroids; bodies of dust and foreign gases called comets (thousands of comets); and drifting particles called interplanetary dust and electrically charged gas called plasma that together make up the interplanetary medium.

The whole solar system by volume appears to be an empty void. This vacuum of ‘space’ comprises the interplanetary medium. The speed of the solar wind is about 400 kilometer per second in the vicinity of Earths' orbit.

The Solar System originated in a primitive solar nebula–a rotating disc of gas and dust. It is from this rotating disc that the planets and the rest of the Solar System evolved. The Solar System is also tucked away in a corner of the Milky Way at a distance of about 30,000 to 33,000 light years from the centre of the galaxy.

The Sun contains 99.85% of all the matter in the Solar System. The planets which condensed out of the same disk of material that formed the Sun, contains only 0.135% of the mass of the Solar System.

Jupiter contains more them twice the matter of all the other planets combined. Satellites of the planets, comets, asteroids, meteoroids, and the interplanetary medium constitute the remaining 0.015%.

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