Difference between revisions of "Solar System"
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The Solar System the Sun and the objects in orbit around the ..
Revision as of 14:43, 18 August 2012
The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago.
A planet is defined as an object that orbits the sun, is massive enough that its own gravity pulls it into a nearly round shape, and is dominant enough to clear away objects in its neighborhood.  There are 8 planets in the solar system. They are, in order of increasing distance from the sun:
The first four planets are terrestrial planets, the last 4 planets are jovian planets. Terrestrial planets are small in size, have high densities, and consist of rocky materials. Jovian planets are large in size, have low densities, and consist of gaseous materials.
A dwarf planet is an object that orbits the sun and has a round shape. The crucial difference between a planet and a dwarf planet is that a dwarf planet is not large enough to clear the neighborhood of its orbit. Currently recognized dwarf planets are:
Pluto was considered a planet until 2006.
Asteroids are irregularly shaped chunks of rocks in the solar system. They exist mostly in 2 places:
- The asteroid belt, which is between the orbits of Mars and Jupiter
- The Kuiper belt, which shares its orbit with Pluto
Comets are astral bodies composed of dust and ice. As they approach the sun the increased temperature causes them to heat and shoot off jets of material, forming a "tail" pointing straight towards the sun. Most comets are in circular orbits out in the Oort cloud beyond Pluto. Some are in an elliptical orbit around the sun, meaning that they will repeatedly enter orbits near the sun until they have evaporated. Some are in a hyperbolic orbit around the sun, meaning that they will only come into the solar system once and will never return, moving on to other solar systems until they have evaporated or are captured in an elliptical orbit.
- The third grade