The study of astronomy is as old as mankind. Our ancestors would gaze at the night sky and "see" all kinds of imagined images. To many of these images they gave names of "beings" of some kind, animals, etc. These have become known to us a "constellations".
Among the night sky, they saw others lights that moved across the sky: some very slowly, others more quickly. Those that moved slowly would include the moon and other objects that we now call "planets", comets and asteroids. Those that move more quickly would inlude what we call "shooting stars" or "meteors" or "meteorites".
The night sky visible to our ancestors (and still visible to us with the naked eye) has turned out to be a very small, very limited portion of what we now call OUR "solar system". Our solar system is composed of several "planets" who travel or orbit what we call our "sun" which is actually a rather small star. Our ancestors, with the naked eye, saw only five of the seven "regular" plants as the additional two are too far away and too dim to usually be seen with the naked eye. The are other "dwarf" planets and "minor" planets that have been discovered which are also a part of our solar system.
The "regular" planets known to us today (listed closest to the sun to the farthest) are:
Mercury, Venus, Earth, Mars, Jupiter and Saturn. Jupiter and Saturn are what astronomer call "gas giants" as they "seem" to be made up completely of "gas" of some kind. The other four planets are known as "rocky" as they seem to have some kind of hard surface.
The are two additional "gas giants" that are usually unable to be seen with the naked eye: Uranus and Neptune.
There are currently five (August 2011) "dwarf" planets in our solar system: Ceres, Pluto, Haumea, Makemake, and Eris but can only be viewed with a telescope. Pluto and Eris are OFFICIALLY the only "dwarf" planets while the others in the "list of five" do not quit match the definition of a "dwarf planet" and are counted as "larger" "minor" planets. It is suspected that at least another forty known objects in the Solar System are dwarf planets. There are probably a "host" of more "dwarf" planets yet to be discovered with many of them residing in the unexplored "Keiper Belt".
There are thousands of "Minor" planets included in our solar system, most of which we call "asteroids". Thousands of these asteroids orbit the sun in a space between Mars and Jupiter but many are also located along with comets in the Keiper Belt which lies close to the edge of our solar system.
In our night sky, the most prominent feature is our Moon which is visible most nights. Due to it's orbit around Earth, there are some nights that it is not visible as it is seen only on the opposite side of earth from the viewer. Many of the planets in our solar system also have one or more moons.
More discussions to come:
Our Sun and relative size to other stars.
What is the "Milky Way".
Other galaxies in our "Universe" and What IS the "universe"
Other planets being discovered around stars other than our sun.
What are asteroids?
What are comets?
More on constellations