Using "What If?", I ran two boards at 4x5 and determined that you are correct. The tautology does not work. This is not a valid solving technique.
One thing stands out in my solution sets for the two clues given. 47 Light Years can only be 650,000 or 714,000. Somewhere in these two clues is the answer to this. There has to be a way of determining this without doing a "What If?" technique.
1) Vestor is either the planet with a diameter of 714,000 mi. or the exoplanet orbiting star PLC 120.
2) Of Vestor and the planet with a diameter of 650,000 mi., one orbits star PLC 120 and the other is 47 light years from earth.
Translating to a nameless approach:
1) A1 is either B1 or C1
2) Of A1 and B2 one is C1 and the other is D1
Somewhere in there is this: D1 is B1 or B2
I'm determined to find out how to summarize this in a logical expression.