HII Regions
| Galaxy characteristics | |||||
|---|---|---|---|---|---|
|
E0-E7 | SO | Sa | Sc | Irr |
| Nuclear Bulge | All Bulge, No Disk | Bulge and Disk | Large | Small | None |
| Spiral Arms | None | None | Tight/Smooth | Open/Clumpy | Occasional traces |
| Gas | Almost None | Almost None | ~1% | 5-10% | 10-50% |
| Young Stars HII Regions |
None | None | Traces | Lots | Dominates Appearance |
| Stars | All Old (~1010yr) | Old | Some young | Some young | Mostly young (but some very old) |