Spiral galaxies usually consist of two major components: A flat, large disk which often contains a lot of interstellar matter and young star clusters and associations, which have emerged from them, often arranged in striking spiral patterns and/or bar structures. The luminosity and mass relation of these components seem to vary in a wide range, giving rise to a classification scheme. The pattern structures in the disk are caused by gravitational interaction with neighboring galaxies.
Lenticular-These are, in short, "spiral galaxies without spiral structure", or smooth disk galaxies, where stellar formation has stopped long ago, because the interstellar matter was used up. From their appearance and stellar contents, they can often hardly be distinguished from ellipticals.
Elliptical galaxies are actually of elliptical shape (for those of you who failed geometry, that means they look like cosmic footballs or eggs). They have little or no global angular momentum (do not rotate as a whole). Normally, elliptical galaxies contain very little or no interstellar matter. They appear like luminous bulges of spirals, without a disk component.
Irregular galaxies-Often due to distortion by the gravitation of their intergalactic neighbors, these galaxies do not fit well into the scheme of disks and ellipsoids, but exhibit peculiar shapes. A subclass of distorted disks is however frequently occuring. 
6 comments:
Nice pics!!! that really helps when you can see something when it is being explained, good work!
:) SarahAnn
Good Job! you have some very good points about galaxies and solar systems. i agree with what you said about galaxies. there is so many things in our universe that we will never be able to see or experience or touch. its scary to think that we're not the only ones our there!!!
JB,
Nice work. Once again, the picture explanations really help. But where's the info on the solar systems???
Rachel
I love the picutes. They are very helpful and useful with knowing what everything looks like. Great work
the one and only
Nick
Jacob, I enjoyed reading your format because it makes it more enticing to read. I love your inclusion of pictures to illustrate your points and effectively get your audience's point of view. I think you had an interesting way of introducing your topic also. You supplied a lot of information on galaxies. I would have liked a little more writing about solar systems, but it was a great post!
~Lindsey~
like everyone else i liked the pictures. it does help with the definitions. overall good post, it was organized.
HAILEYROSE THOMA
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