Solar System Overview
Welcome to the solar system! It’s a really interesting place, and there’s a lot to cover. First lets get a basic idea of what our solar system looks like. There are eight planets in the solar system and five “dwarf planets” and they all orbit around the sun. The four planets closest to the sun are called the “inner” planets. They are all pretty small and made mostly of rocks. Earth is the third inner planet. Here’s a picture of their orbits (click for a bigger version):
Between the inner and outer planets is a region with a lot of rocks floating around, left over from when the solar system was forming. It’s not like in Star Wars, though. If you were on an asteroid in the belt, you probably wouldn’t be able to see any of the other ones without a telescope. The outer planets are much larger than the inner ones. They are huge balls of gas with dense cores. Because they are so large, they have very strong gravity, so most of them have many moons. Out beyond the giant planets is the dwarf planet Pluto. It doesn’t really fit in with the rest of the outer planets because it is tiny, smaller than earth’s moon. It also has a strange orbit, which makes scientists think it is part of a cloud of rocks and bits of ice called the Kuiper belt. Here is a picture of the outer planet orbits. You can’t see the orbits of the inner planets because they are too small. All the inner planets are right near the sun, inside Jupiter’s orbit.
Below you can see pictures of the sun and all the planets (and some of the dwarf planets) in our solar system. This shows them all at about the right sizes relative to each other, but much closer together than they actually are.
Planets in General
This post was originally part of a website made for the UMich Student Astronomical Society 2005 Astrophysics inreach by Ryan Anderson, Sarah Springsteen, and Ben Ruskin. Pictures were shamelessly stolen from various sites. It has been updated with more current information as of May, 2010.