Galaxies come in many shapes and forms.

There are spiral galaxies, elliptical galaxies, irregular galaxies, barred galaxies, and dwarf galaxies. Spiral galaxies have two main components. One of them is a flat, large disk that often contains a lot matter and a lot of star clusters that emerge from dark, dusty clouds. Also, it is known as the "Diffuse Emission Nebulae." The stars in the cloud are classified as stellar population. Elliptical galaxies are actually in an ellipsoidal shape. They also might be in a triangular shape. These galaxies have little or no global angular momentum. They also contain little or no interstellar matter. Irregular galaxies usually due to distortion by gravity from other galaxies, they do not fit well into the scheme of ellipsoids and disks. But, irregular galaxies exhibit peculiar shapes and sizes. A subclass of disks that are distorted frequently happens. Barred galaxies are a different kind of spiral galaxies. But, their middle is a bar instead of a sphere. Some scientists now believe that are galaxy is a barred galaxy. Around 2/3 of the galaxies have bars. That means that bars are formed easily. There are two ideas why bars form in galaxies. One of them is that they are formed from interactions with other galaxies. Dwarf galaxies are small and faint. There are two main types of dwarf galaxies. One is a dwarf irregular galaxy that tends to contain a lot of gas and usually shows strong signs of star formation. The other one is a dwarf elliptical galaxy which tends to be lower in mass.

Galaxies contain many things like; stars, planets, moons, comets, asteroids, nebulas, dust, neutron stars, and black holes. A galaxy contains billions of stars. Sometimes instead of being far away from each other, stars are in clusters. The planets in our solar system are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and our dwarf planet Pluto. Six of our eight planets have moons. Moons are space rocks that are caught in a planet’s gravitational pull. Comets are lumps of dust and ice that come to the center of the solar system. Asteroids are somewhat like comets. They are basically the leftovers of the solar system. A nebula is a cosmic cloud. The word "nebula" comes from the Latin word "cloud." Another thing that is in a galaxy is a galactic halo. A galactic halo is a dust free and spherical region surrounding a spiral galaxy.

When a galaxy is formed, it is called a galactic formation. By the time the universe was a few hundred million years old, some of the densest regions had ceased expanding and began to collapse. A lot of the collapsing regions tended to cluster together. At first, knots of the collapsing regions spread out from these knots. After some time, it linked the knots together. Most of us believe that the ordinary matter of which the earth and stars is made up of less than 10%of the matter in the universe.

Our galaxy is the Milky Way. It is a spiral galaxy. It contains about 200 billion stars. The Milky Way also contains three main components. One of them is a disk with four spiral arms. The Milky Way is actually a giant.

Some people define galaxies as large system of stars and interstellar matter. A galaxy usually contains several million to several billion stars. Galaxies have more than just stars. They contain various types of star clusters and nebulas. Galaxies have many basic features. One of them is that they are all huge agglomerations. A galaxy is also a place that is mostly just open space. Lastly, galaxy is a place that mankind can explore.

Credits:

http://zebu.uoregon.edu/~soper/Galaxies/types.html

http://www.seds.org/messier/galaxy.html

http://www.astronomynotes.com/galaxy/s10.htm

http://imagine.gsfc.nasa.gov/docs/resources/resources_a.html#galaxies

http://www.damtp.cam.ac.uk/user/gr/public/gal_milky.html

http://campus.lakeforest.edu/~bell/astro/johnb/Barred.htm

http://www.answers.com/topic/dwarf-galaxy

http://www.daviddarling.info/encyclopedia/D/dwarfgal.html

http://www-thphys.physics.ox.ac.uk/user/Galactic/layman/formation.html

http://members.aol.com/_ht_a/bobalien99/galaxies.htm#WHAT%20IS%20A%20GALAXY?

http://www.daviddarling.info/encyclopedia/G/galaxy.htm