According to the account in Matthew, the star “was going before them,” and “stopped at the place where the child was.” Comets of course traverse the sky, and supernovas and conjunctions do appear to move - thanks to the earth’s motion. But that a lighted object high in the sky could give someone to a precise location just doesn’t compute. (In any case, the gospel says that the guiding star “stopped at the place where the child was.” The magi needed no help to find the village of Jesus’ birth, since the men in Jerusalem already mentioned that it was in Bethlehem; they needed help only to determine which child in Bethlehem was the one they were seeking.) St. John Chrysostom I think had the right observation when he said:
For if you can learn what the star was, and of what kind, and whether it were one of the common stars, or new and unlike the rest, and whether it was a star by nature or a star in appearance only, we shall easily know the other things also. Whence then will these points be manifest? From the very things that are written. Thus, that this star was not of the common sort, or rather not a star at all, as it seems at least to me, but some invisible power transformed into this appearance, is in the first place evident from its very course. For there is not, there is not any star that moves by this way, but whether it be the sun you mention, or the moon, or all the other stars, we see them going from east to west; but this was wafted from north to south; for so is Palestine situated with respect to Persia.
In the third place, from its appearing, and hiding itself again. For on their way as far as Palestine it appeared leading them, but after they set foot within Jerusalem, it hid itself: then again, when they had left Herod, having told him on what account they came, and were on the point of departing, it shows itself; all which is not like the motion of a star, but of some power highly endued with reason. For it had not even any course at all of its own, but when they were to move, it moved; when to stand, it stood, dispensing all as need required: in the same kind of way as the pillar of the cloud, now halting and now rousing up the camp of the Jews, when it was needful.
In the fourth place, one may perceive this clearly, from its mode of pointing Him out. For it did not, remaining on high, point out the place; it not being possible for them so to ascertain it, but it came down and performed this office. For you know that a spot of so small dimensions, being only as much as a shed would occupy, or rather as much as the body of a little infant would take up, could not possibly be marked out by a star. For by reason of its immense height, it could not sufficiently distinguish so confined a spot, and discover it to them that were desiring to see it. … How then, tell me, did the star point out a spot so confined, just the space of a manger and shed, unless it left that height and came down, and stood over the very head of the young child? And at this the evangelist was hinting when he said, “Lo, the star went before them, till it came and stood over where the young Child was.”
In fact, the ancient tradition John Chrysostom was describing here (first attested in the Protoevangelium of James - as always - and repeated by other Fathers and writers such as St. Irenaeus, Origen, St. Ephrem, and Theophylact, even down to the days of John Calvin!) has the ‘star’ actually leaving the heavens and coming down to earth to lead the Magi to a particular house, perhaps even to the infant Jesus Himself. In other words, they thought that the ‘star’ was more like Tinker Bell in the Peter Pan stories than any natural celestial phenomenon known to astronomy.
The star descended from the heights and came closer to the earth to show the place to them [the magi]. For if it had appeared to them in the heights, how would they have been able to perceive the particular spot where Christ was? For the stars are visible over a great area. You may accordingly behold the moon over your house while it appears to me that it is over my house only. In short, the moon or a star appears to one and all to stand over them alone. So this star could not have indicated where Christ was unless it descended and stood over the head of the child. (Theophylact, Commentary on Matthew 2.9)
And at His birth the star appeared to the Magi who dwelt in the east; and thereby they learned that Christ was born; and they came to Judaea, led by the star; until the star came to Bethlehem where Christ was born, and entered the house wherein was laid the child, wrapped in swaddling-clothes; and it stood over His head, declaring to the Magi the Son of God, the Christ. (Irenaeus, Proof of the Apostolic Preaching 58)
[The star] came down to the very place where the infant was [and it remained] on the Christ [just as, when he later submitted to John’s baptism, the Holy Spirit in the form of a dove descended] and remained on him. (Origen, Homily on Numbers 18.3 )