I think it’s folly trying to determine a natural–or totally natural–explanation for the Star.
St. John Chrysostom said that the star was a special vision given to the Magi. There might have been some natural astronomical phenomenon that God used to get their attention, but I believe that the star that “went before them” and “stood over the place where the young Child was” was a vision given to them alone.
The Troparion for the Nativity explains it best:
Your Nativity, O Christ our God
Has shown upon the world the light of wisdom,
For by it, those who worshipped the stars
Were taught by a star to worship You,
The Sun of Righteousness,
And to know You, the Orient from on high.
O Lord, glory to You!