The Nyquist theorem, in very simple terms, describes the minimum measurements you need to take to capture all the information in a signal. It turns out, if you have special information about what signal you expect to see, you can still figure it out using fewer measurements.
Generally speaking, it tells you how many measurements you need to take to capture the whole signal.
I think there was originally some confusion because graphics of the sistership were reused for news reporting because they thought it was close enough.