FamousAlien1979 · Jerry Goldsmith
Goldsmith's original Main Title (replaced in the released film by a more abstract version), the solo trumpet entry about 0:35-0:45 into the cue over a held C
Goldsmith never actually plays this chord. In his original main title, basses and very high strings hold a bare C four octaves apart while a solo trumpet rises through B♭, E and A, and your ear stacks those notes over the C into a C13 (seventh, third and thirteenth) floating in empty space. A G♯ a bar later bends it out of shape, which adds to the unearthly feel.
Also called Alien 13, the implied C13 of the Alien main title
Sources: Brian Morrell, How Film & TV Music Communicate vol. 2 (2013), ch. 5 'In Space Everyone Can Hear the Chord Changes (part 1)', Fig. 1 · MUBI Notebook, 'In Space You Can Hear a Symphony: The Story Behind the Theme for Alien' · Cue By Cue: Alien (Goldsmith, 1979) · Alien (soundtrack), Wikipedia