The Bridge V Learning 2(clone) - Page 6

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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