The imperial attack immediately following the open scroll of "A New Hope" uses a chord that is note-for-note identical with the coda of "Mars" from Gustav Holst's The Planets. First, the Star Wars excerpt, lasting from 1:41-1:56 of the following clip:
Now compare that with 6:56-7:11 from "Mars":
For visual reference, here are the two score excerpts side-by-side:
Both pieces use the exact same dissonant chord: A-flat, D-flat, G from bottom to top, with a C in the bass. In Star Wars, for the last few measures Williams adds a C above the dissonant chord as well to keep the chord building in intensity.
The Music of Star Wars
These posts will help focus and develop my analyses of John Williams' film scores.