Tuesday, June 22, 2010

Solar System

The solar system is dominated by the gravitation of the Sun. About 99.85 percent of the mass of the system resides in the sun, 0.14 percent in the planets and the rest in satellites, asteroids, comets and meteoric matter that also circle the central star.
The planets all circle the sun in the same direction, and almost exactly the same plane. Viewed from “above” that is the side on which the Earth’s Northern Hemisphere lies, the direction of the planetary motion is counter clockwise. The asteroids, or minor planets, do the same. But the orbits of the comets are oriented randomly. They can approach the sun, and recede from it, at any angle.
The furthest planet from the Sun, normally, is Pluto, which at its maximum reaches 7,375 million Km from the Sun. but the furthest members of the sun’s group are believed to be an enormous group of unseen comets which form Oort’s Cloud, named after the Dutch astronomer who deduced their presence. The comets spend most of their time in the outermost reaches of their orbits, at a distance of about two light years from the Sun. They mark the true outer limit of the Solar System, the region in which the Sun’s gravity becomes feebler than that of its neighboring stars