How Do Galaxies Evolve on the Hubble Tuning-Fork Classification Scheme

question 83

Multiple Choice

How do galaxies evolve on the Hubble tuning-fork classification scheme and what is the evolutionary significance of this diagram, shown in Figure 17-15 of the text?

• A) About three-quarters of galaxies do not evolve, but others can change their position. Usually, spiral galaxies merge to form ellipticals.
• B) The "young" irregular and lenticular galaxies in the center of the tuning fork evolve to either elliptical galaxies if the material is metal-poor or spiral galaxies if the material is metal-rich.
• C) Stars slowly die and the spiral arms slowly spin up and tighten to transform spiral galaxies into elliptical galaxies.
• D) Elliptical galaxies slowly condense and spin up to form spiral galaxies, the increasing stellar collisions forming the interstellar material in the spiral arms.