An unlabeled hierarchical diagram of various astronomical bodies is shown below. The labels A, B, C, and D can be used to represent the Milky Way, universe, planets, clusters, and stars. An image of four circles nestled one within the other is shown. The lower boundary of all four circles touch one another. The largest and the outermost circle is labeled A. The next circle in order is labeled B. The next circle is labeled C. The innermost circle is labeled D.

Part 1: Which four astronomical bodies would you choose to represent the four labels in the diagram?
Part 2: Justify your choice based on the hierarchical relationships in astronomical bodies.