That fixed it, thanks! That was perfect.
I've learned another solving technique. This one is super twisted.
I'll expand on how this worked out. I like to spell things out and this one twisted my head too much to just "see" it. I'll get it right with practice.
Begin with Clue 7:
Of the planet 45 light years from earth and the exoplanet with a diameter of 310,000 mi., one orbits the star PLC120, and the other is Ereph.
Restate it in terms of Ereph (and simplify the long text a bit):
Ereph is either 45 years or 310,000
Next, let's go to Clue 8:
Of the planet orbiting star VJD 913 and the exoplanet 47 light years from earth, one has a diameter of 295,000 mi. and the other is Ereph.
And restate (and simply wording) the clue in terms of 47 light years:
47 years is either 295,000 or Ereph.
Substitute from above and we get:
47 is either 295,000 or 45 year or 310,000.
Drop the contradiction and get 47 is either 295,000 or 310,000. Put that into the grid.
This wasn't enough for me to solve the puzzle, so, as instructed, I flipped this technique around and began again, but this time with Clue 8.
Restate Clue 8 in terms of Ereph:
Ereph is either VJD 913 or 47 years.
And restate Clue 7 in terms of 45 light years:
45 years is either PLC 120 or Ereph.
Substitute from above:
45 is either PLC 120 or VJD 913 or 47 years.
And remove the contradiction:
45 is either PLC 120 or VJD 913.
Plug this into the puzzle. Now there are enough eliminations on the grid to get the other clues to finish the puzzle without any more complicated techniques.