Starship Asterisk*

This is just a WAG: I would be willing to bet that there were two shock-fronts not quite at the same point associated with the rocket passing through the thin layer of super-saturated air. When the wave-fronts of the shock waves added, they didn't do much, but when they subtracted, they decompressed...

pmason has the answer. As I observed earlier, the shape is like the upper tangent arc, but sharper than any examples in the photos I've seen. I didn't realize the angle above or below the observer's horizon made the arc sharper or more obtuse. That explains it perfectly. Comparing photos with light...

Now that several people on this forum have agreed with my earlier explanation , I'm going to disagree with myself :) Looking more at the extra photos linked from the APOD page, the "fan" section looks too crisp and orderly to be just the result of dispersed orientations of the crystals hi...