How does the amount of dust and gas in a spiral galaxy vary with the classification of the galaxy?
A) The most loosely wound galaxy, Sc, has the most dust and gas in its arms.
B) All spiral galaxies Sa, Sb, and Sc types have about the same fraction of gas and dust within them, about 4% by mass.
C) Only the most tightly wound spiral galaxies, type Sa, have any dust or gas in them at all.
D) The most loosely wound galaxy, Sc, has the least dust and gas in its arms.

Question

Quizplus · Accepted Answer

The amount of dust and gas in spiral galaxies increases from Sa (tightly wound) to Sc (loosely wound) types, with Sc galaxies having the most dust and gas in their arms. This is because the classification from Sa to Sc reflects not only the tightness of the spiral arms but also differences in the composition and age of the stellar populations, with Sc galaxies being younger and more gas-rich.

How Does the Amount of Dust and Gas in a Spiral