This star was not a common one–it was not even 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 no star moves like this. For, we see the sun, moon, and all the other stars travel from east to west; but this was drifted from north to south–for so is Palestine situated with respect to Persia.
Secondly, it did not appear in the night, but in mid-day, while the sun is shining. This is not the power of a star, nor of the moon–for when the beams of the sun appear, the moon immediately hides herself, and vanishes away even though it surpasses all stars in its light. But this, by the excess of its own splendor, overcame even the beams of the sun, appearing brighter than they, and in so much light shining out more illustriously.
St. John Chrysostom, Commentary on the Gospel of St. Matthew, NPNF, s. 1, v. 10, p. 102-104.
In the third place, from its appearing and hiding itself again. For it appeared and led them on their way as far as Palestine. But after they set foot in Jerusalem, it hid itself. 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 of this 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 that was needed. It was similar to the pillar of the cloud, now halting and now rousing up the camp of the Jews, when it was necessary.
In the fourth place, one may perceive this clearly, from its mode of pointing Him out. For it did not point out the place from above, for then they could not determine the place where He was. 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. And this any one may see by the moon, which being so far superior to the stars, seems to all that dwell in the world, and are scattered over so great an extent of earth, — seems, I say, near to them every one.
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, “Behold, the star went before them, till it came and stood over where the young Child was.” See by what store of proofs this star is shown not to be one of the many, nor to have shown itself according to the order of the outward creation?
And why did it appear? To rebuke the Jews for their insensibility, and to remove any excuse for their willful ignorance. Since He who came was to put an end to the ancient polity, to call the world to the worship of Himself, and to be worshipped in all land and sea, He immediately from the beginning opens the door to the Gentiles and admonishes His own people with strangers.