Why do most galaxies have a flat, disc-like shape?

[bobie]

Most ( or probably all?) galaxies are shaped like flat discs (10/30 times wider than thick).
Are their planes all aligned on the same angle (from our point of view) or they vary?
If so, is it just casual orientation or it follows a certain pattern, for example the angle grows proportionally to distance?

 

[Drakkith]

The orientation of galaxies is completely random. There is no known pattern as far as I know.

 

[SteamKing]

Most ( or probably all?) galaxies are shaped like flat discs (10/30 times wider than thick).

There is a classification of galaxies by their shapes:

http://en.wikipedia.org/wiki/Galaxy

Are their planes all aligned on the same angle (from our point of view) or they vary?
If so, is it just casual orientation or it follows a certain pattern, for example the angle grows proportionally to distance?

The orientation of different galaxies appears to be somewhat random, as can be seen by examining
astronomical photographs from the Hubble Space Telescope:

http://blogs.discovermagazine.com/b...e-the-hubble-extreme-deep-field/#.U7O60bGGcr4

Some galaxies appear nearly edge-on from our perspective, some are at an oblique angle, and some appear to be almost perpendicular to our line of sight.

 

[bobie]

There is a classification of galaxies by their shapes:
Some galaxies appear nearly edge-on from our perspective, some are at an oblique angle, and some appear to be almost perpendicular to our line of sight.

Thanks, so a near galaxy can be perpendicular and one 10Gly away can be horizontal!
Distance has no influence at all.

 

[davenn]

Thanks, so a near galaxy can be perpendicular and one 10Gly away can be horizontal!
Distance has no influence at all.

none at all

 

[davenn]

bobie

sounds like maybe you haven't seen any images of galaxies
here's one taken by the Hubble Space Telescope
This shows just a tiny portion of sky, just about every object in this image is a galaxy
note all the different orientations
also note the different types of galaxies ... spiral, elliptical etc

There's probably 1000's of galaxies in this image

cheers
Dave

 

[ajclarke]

There was some really interesting work by the galaxy zoo team on this. They asked people to classify disk galaxies as being rotating counter clockwise (s like) or clockwise (z like). They actually found that there are more s like galaxies. To uncover this, they took the sample and flipped the images ( s -> z like ; z -> s like ) and found that people still classified the s type as being more prominent.

There could be many factors that contribute to this, from the placement of the websites voting buttons to people finding it easier to pick out certain shapes in images. But the end result was that there is no inherent bias in how galaxy rotate or are oriented.

More information: http://blog.galaxyzoo.org/2008/01/10/in-the-eye-of-the-beholder/