a) The official novelisation of the Alien movie by Alan Dean Foster offers us a secondary source of speculation since it was written and released as the film at the time of the movie, however little is known about what of the dialogue was his own creative contribution.
b) Page 20, Kane gives an explanation of a possible reason why they can't work out where they are because they possibly came out of Hyperspace backwards and they were seeing Centauri at top amplification which would have been the direction where they were coming from and so Earth would be behind them. Perhaps in Alan Dean Foster's novelisation, they travelled through space from the direction of Alpha Centauri which is known to be 4.24 light years away from Earth, but of course from somewhere a lot further than that.
c) Page 22, a variation of Lambert's description of their location is "We're just short of Zeta II Reticuli. We haven't even reached the outer populated ring yet. Too deep to grab onto a navigation beacon, let alone a Sol traffic relay."
d) Whether Alan Dean Foster was lending his own interpretation to what the outer ring was or not, or if this was what he read in a version of the script that he had been given to novelise is still unknown.