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Galaxies

A galaxy is a huge group of billions of stars and other astronomic objects (nebulae of many types), that are together due to gravitational forces and keep spinning around a centre of a common mass.

            Is it estimated that there are approximately 1 billion of galaxies. Our galaxy is called Milky Way and there is a theory that it is going to collide with another galaxy called Andromeda.

Galaxies are divided in some different morphological types:

• Spiral Galaxies.
• Elliptical Galaxies.
• Irregular Galaxies.
• Dwarf Galaxies.

Examples:

• The Magellanic Clouds are two Dwarf galaxies of Milky Way that can only be seen by the south hemisphere.

Magnificant Details in a Dusty Spiral Galaxy

http://grin.hq.nasa.gov/IMAGES/SMALL/GPN-2000-000933.jpg

Ring around a Galaxy

http://grin.hq.nasa.gov/IMAGES/SMALL/GPN-2000-000944.jpg

Variable Stars in a Distant Spiral Galaxy

http://grin.hq.nasa.gov/IMAGES/SMALL/GPN-2000-000940.jpg

Galactic Silhouettes

http://grin.hq.nasa.gov/IMAGES/SMALL/GPN-2000-000893.jpg

A Grazing Encounter Between Two Spiral Galaxies

The Wonderful World of Astronomy - ThinkQuest
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2009