Solar System Objects
Our solar system consists of our sun, the moon, 7 planets besides the Earth, comets and asteroids.
The Sun aka Sol is really just a star that is really really close to us. Really, really close is about 93 million miles. But that is a lot closer then any other star. 93 million miles may sound far, but that is 16 MILLION times closer then the nex cloestest star. Stars are really just giant balls of gas, mostly hydrogen, which are burning (however, they are no on fire as much as they are undergoing nulclear reactions).
Planets are balls of rock similar to Earth which orbit a star. With the recent demotion of Pluto from planet to dwarf-planet there are now 8 planets in our Solar System. They are; Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. The first four are the inner/rocky planets. The last four are the gasious planets. Gasious planets are mostly gas. Although they are believed to have a rocky core, they have a very thick atmosphere, covered in clouds. When we look at them through telescopes we are looking at the thick layers of clouds.
Moons are smaller balls of rock which orbit around planets. Earth has only one moon, which we call The Moon. Mars has two moons, Venus and Mercury do not have any moons. The Gas giants have dozens of moons each. You can usually see some of the larger moons of Jupiter or Saturn when you look at the planets through a telescope.
Dwarf Planets are smaller planets. Technically they are planets which are large enough that their gravity makes them more or less round and that have cleared out the majority of interstellar material from around their orbit. Pluto, which use to be called a Planet is now classified a Dwarf Planet. There are approximately a dozen objects in our solar system which fit this description. In reality there can be hundreds, thousands, or maybe even tens of thousands of these objects in our solar system but they have not yet been discovered because they are so small and so far away.
Asteroids are even smaller then dwarf planets. They are small and not quite round. In fact they can be just about any shape. The vast majoirty of asteroids lay in the asteroid belt between Mars and Jupiter. However, they can be found anywhere in our solar system.
Comets are often called dirty snowballs. They are frozen gas and water which come from far beyond the planets. The gravity from the sun pulls them toward it, and when they get close the gas and ice blows off forming what looks like a giant tail. Some comets can take centuries to return, as they slingsot around the sun and are thrown far back into outer space.
There are many different classifications of nebulas. However, in the end they are all the same, massive amounts of somewhat dense gas in space. The can be caused by stars exploding or be gas left over from planet and solar system creation. "Nebula" was a term used to first describe every strange thing in the night sky. Because of that some galaxies still retain their old "nebula" names, but now "nebula" is a term reserved for concentrations of gas.
Emission Nebula are clouds of gas which are lit form nearby stars. They are usually red due to the large amount of hydrogen in them. They do not actually reflect light, but instead the gas is heated by the stars and as the heated particles cool they emit a glow.
Reflection Nebula are clouds of dust, not gas which reflect light. They are usually blue because that wavelength of light reflects against the dust better then others.
Diffuse Nebula can be either Emission or Reflection Nebula. This is a general term used to describe both.
Dark Nebula are reflection nebula which are not reflecting light because there are no nearby stars to reflect from. We can usualy only see dark nebula when they are infront of a diffuse nebula.
Planetary Nebula are so called because they almost look like a planet, but not as bright. They are formed as starts shed off some of their gas, and are lit because the star remains to burn.
Supernova Remnants are the remains of stars which have exploded. Like a planetary nebula they are formed from stars, however, the supernova results in the stars destruction and as such form a more irregular shaped nebula.
Stars are giant balls of gas which are so massive that they begin to undergo nuclear reactions. They emit, among other things, light. Depending on this size, age and makeup of the star it can be many different colors. From reds to oranges, yellows and blues. When stars die they can become black holes, or explode to make nebula.
Stars can vary in size as well as color. Some stars are so huge that they are in a continual balance between blowing themselves away and being bound together by gravitational pull. As a star burns its fuel it pushes outward, the way bubbles boil to the surface of a boiling pot of water, gas is being pushed away from the star. However, at the same time the gravity of the star is pulling that gas back towards it. When a star becomes to large, the fusion reaction is too strong for gravity and the star sheds it's gas into space.
Stars will group together because their gravity will attact them to each other, in this form they form galaxys. But inside of galaxies stars can group together to form clusters. Star clusters are usually formed during the birth of stars from giant areas of space filled with large amounts of gas. As the stars form from the gas, sometimes there is enough gas to form hundreds or thousands, or in some cases thousands of stars.
There are generally two types of star clusters.
Globular Clusters These are tightly packed stars in a 'small' area of space. The largest cluster is visible on very dark nights. Omega Centauri is 17,000 lightyears away, spans an area of 150 light ears and contains an estimated 10 million stars.
Open Clusters contain less stars the a globular cluster does. There are usually dozens of stars in smaller numbers up to a hundred thousand stars or more in some open clusters. Instead of appearing as a haze of tiny stars, open clusters usually form shapes (and thus are named for their shapes) such as the Coat Hanger Cluster, Christmas Tree Cluster and Number Seven Cluster.
Galaxies are groups of stars, and star clusters. They contain hundreds of billion of stars and are so far away that only a handful of the millions (or billions, or trillions) of galaxies are visible to the naked eye. Just like stars, galaxies often appear in clusters themselves with dozens of galaxies being in close proximity to each other.
Galaxies have been classified into 4 main types of galaxies.
Spiral Galaxies are the shape of what most people think of when they hear galaxy. They have spiral arms which extend from its center and circle around the galaxy's core.
Barred Galaxies are very similar to spiral galaxies, except they include a 'bar' of stars across the core.
Elipical Galaxies are galaxies which have not formed spiral arms for one reason or another. They appear as a dense star cluster would.
Irregular Galaxies cover just about every other type of galaxy. These galaxies usually do not form any common shape but instead are just a collection of stars.