We should also accept the fact that at the time of Sri Yukteswar living in the body there most likely was no understanding or concept of the center of our galaxy. Therefore he used a word like Vishnunabhi to designate it in his own terms. That's my take on it. We did not have the technology to have pictures and an understanding of our universe-though small- as we do today.
KK, that's a plausible hypothesis. Although, if the entirety of SY's theory should be accepted (that is: revolution of sun A and sunB aroudn a common baricenter) then Vishnunabhi should be by logic much closer to our system than Sagittarius A*, the central black hole, the hub of our galaxy. This because, as we have already discussed, a revolution around a dual would cause a change in distance from Sagittarius A* pretty much negligible, given the distance, even in the astrological perspective . Whereas a closer Vishnunabhi would imply a variation in distance which is more significant.
Vishnunabhi might even be an astral region with no physical counterpart. Unfortunately SY is no more around with his body and we cannot ask him, although we might be able to get in touch with him by deep meditation.