Weegy: The solar system is the sun and any objects in orbit around the sun or in orbit around an object orbiting the sun. Most prominent of these objects are the planets. [ The nine planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto. In addition to the planets are many objects of smaller size but also in orbit around the sun. These objects include the asteroids and comets. In addition there is dust and debris orbiting the sun, but we shall consider this insignificant and uninteresting.
How big is a solar system? If we consider only the planets, then the extent of the solar system is approximately 39 astronomical units. This would be the orbit of Pluto. However, if we consider comets, then the solar system is a much larger body. Cometary orbits may be on the order of 100,000 astronomical units. This is about one and one-half light years, or roughly one-third the distance to the nearest stars. To gain some insight into the size of the solar system consider the tip of your nose as the sun. Imagine the Earth to be one inch from your nose. Pluto would be a little more than one yard from your nose. The farthest comets would be more than one and one-half miles away.
Where did the planets, asteroids, and comets come from? Consider 3 main theories for their origin.
The first theory is the captures theory. Under this theory, the planets and other objects came within the gravitational pull of the sun. They were then unable to escape the sun's gravitational attraction. Under this theory however, it would be likely that the orbits of the planets would be in random orientation. However, we know that all the planets orbit the sun in roughly the same plane and in the same direction. Therefore this theory can be discarded.
A second theory had the planets spinning off the sun during the sun's evolution. This would explain why all the planets orbit in roughly the same plane. However, if this theory were correct then all the planets would be of ...
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