Q: What exactly was the Bethlehem star?
A: There are a number of plausible theories, but we don't know with absolute certainty what it was. I’ve heard a number of very convincing suggestions but, personally, in my opinion, I believe that the “star” was supernatural. The star was seemingly something that was only noticed by the wise men. Due to the earth’s rotation, most celestial bodies move from east to west, but the star of Bethlehem led the wise men from Jerusalem south to Bethlehem. Not only that, but it led them directly to the place where Joseph and Mary were staying, stopping overhead. There is no natural stellar phenomenon (i.e. comet, planet, conjunction of planets, etc.) that are known to do that, yet God does (cf. “pillar of cloud and fire” in Ex. 13:21 and “Ezekiel’s wheels” in Ezek. 1:20). God has been known to lead specific people to specific locations and I believe that God used this special and unique sign to direct the wise men to the Christ child.