Galaxy Zoo Starburst Talk
Imagine a cross-section of shaving bubbles in galactic scale - this pic shows faint outlines of the bubbles encircling dark empty centers.
A spiral arm is being "pulled" out by the large object on the lower right.
Bottom star/galaxy is "pulling" some material from the lower left.
This one looks like it is forming a spiral arm.
Interesting, that the constellation in the bottom looks like an ellipse of paired stars.