CLASSIFYING GALAXIES
SHARE YOUR CLASSIFICATION SCHEMES WITH ANOTHER GROUP
• What similarities are there between between schemes?
• Significant differences?
• How to classify particular galaxies?
• Why did you decide to design your schemes the way you did?
• Are there completely different types of schemes you could devise?
• Why is it important (or not) to classify objects we discover?
• Might classification schemes be changed over time?
• Did the galaxies form in different shapes, or did they all form in the same shapes and then evolve into different shapes?
• What different histories could different galaxies have (especially, that could affect their shapes)?
• Could the evolution of galaxy shape be due to internal processes or driven by external processes?
• Could the shapes be related to the size of the galaxy when it forms?
• Are the shapes we observe transient or long-lasting?
• Elliptical (E): galaxy with a spherical or elliptical shape (like an American football); it has no flat disc or spiral arms.
• Lenticular (S0): galaxy with a smooth, flat disk shape without spiral structure; often hard to distinguish from ellipticals.
• Barred Lenticular (SB0): same as above, but with an elongated (barred) nucleus (galaxy centre).
• Spiral (S): galaxy with a flat disk shape, with notable spiral patterns in the outer disk; also contains a large bright central bulge.
• Barred Spiral (SB): A special type of spiral characterised by an elongated nucleus with the spiral arms springing from the ends of the bar.
• Irregular (IR): an oddly shaped galaxy that doesn't fit into any other category.
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