Question about galaxies

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Galaxies are all relatively the same size, ranging from a few thousand light years in diameter, to a hundred thousand light years or so. There seems to be some factors involved as to how large they can become, although I’m not sure it has anything to do with mass?
Can someone please explain galaxy formation and more specifically what contributing factors play a role in their actual sizes?
 

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  • #2
Labguy
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Vast said:
Galaxies are all relatively the same size, ranging from a few thousand light years in diameter, to a hundred thousand light years or so. There seems to be some factors involved as to how large they can become, although I’m not sure it has anything to do with mass?
Can someone please explain galaxy formation and more specifically what contributing factors play a role in their actual sizes?
These would be a thorough start.
http://www.noao.edu/swift/proposal/node6.html

http://nedwww.ipac.caltech.edu/level5/March02/Efstathiou/TOC.html

http://origins.stsci.edu/under/galaxies.shtml [Broken]

http://www.universetoday.com/am/publish/formation_galaxies_evidence.html

http://csep10.phys.utk.edu/astr162/lect/galaxies/evolution.html
 
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  • #3
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Some very helpful links Labguy!

When astronomers study the Milky Way, they can learn about the birth, life and death of its stars because they see the stars at various evolutionary stages. Detailed studies of the ages and chemical compositions of these stars suggest that the Milky Way has led a relatively quiet existence, forming stars at a rate of a few suns per year for about the last 10 billion years.
So over a time scale of about 10 billion years our galaxy should form around 30 or 40 billion stars, not to mention recent observation of increased star production in early galaxies.
This and occasional collisions and cannibalism, contribute to galaxies of ever increasing sizes. But why is it we don’t see galaxies on the really enormous scales?

Would it be possible that gravitational strengths influence the relative size of a galaxy? The bulk or the core of a galaxy acting similarly to a sun in a solar system, the combined gravitational force can only capture a certain number of stars, so even when mergers do occur, a galaxy can’t just keep adding to it’s mass exponentially?
 
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This kind of surprised me!

What is the largest galaxy?

What is the largest galaxy, near or far, discovered to date? How large is it?

The largest galaxies that we know of are giant elliptical galaxies in the centres of clusters of galaxies. They are sometimes called cD galaxies (for giant diffuse galaxies) or BCGs (for brightest cluster galaxies). These galaxies are about 10 times more luminous that a typical galaxy (like the Milky Way) and about 100 times more massive. They can have diameters of more than 6 million light years (compare to about 100 thousand light years for the Milky Way). A good example is the central galaxy in the cluster Abell 2029.

cD galaxies are thought to grow by accreting any galaxy that comes anywhere near them, and in the centre of a cluster this can be a lot of galaxies over the age of the universe - so their mass can grow by a large factor. They usually have an area around them in which no smaller galaxies are found (as they've all been 'eaten') and a diffuse halo of gas and dust which is thought to be the debris of the smaller galaxies.
http://curious.astro.cornell.edu/question.php?number=412 [Broken]
 
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