Planets In The Universe
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| The Planets |
Some
4.6 billion years ago, a spinning cloud of cosmic dust and gas
contracted to form a young star and its retinue of planets. What emerged
was the Solar System of which the Earth is a part.
Our Sun weighs almost 1000 times as much as the rest of the system put together. Its massive gravitational force controls and guides the nine planets, dozens of satellites and comets, and many hundred thousands of asteroids. The path of each Planet around the Sun is determined by a balance between the inward pull of the Suns gravity, and the outward centrifugal force of each planets orbital speed. Planets closer to the Sun where the inward pull is stronger move faster than those further out. The influence of the Sun is all important. As well as controlling the orbital velocities of the planets, it has shaped their characters, so that their chemical composition and mass vary according to their distance from the Sun. Despite this subjection to the Sun, the individual planets have their own idiosyncrasies. Unlike the Earth and the other planets that rotate on their axes from west to east, Venus and Uranus spin in the opposite direction. In addition Uranus spins like a skidding wheel around the Sun, whereas every other planet spins like a top while rotating around the Sun. It is only 70 years or so since Pluto the ninth planet was discovered. There is still much speculation about a potential tenth planet in our Solar System. Some Astronomers are convinced that a slight wiggle in the orbits of Uranus and Neptune is caused by the gravitational pull of a very dim and distant planet way beyond Pluto. Interestingly there is also some speculation within Astrological circles of a similar nature. It is almost certain that our Solar system is not unique. The same system for detecting the presence of planets used to detect a possible tenth planet in our Solar System has successfully detected planets in orbit around distant stars. |