1. The star was visible to the Wise Men, but not to Herods astrologers so only the Wise Men reacted to it.
2. The star was visible to both the Wise Men and Herods astrologers then:
The Wise Men placed significance on the event, but Herods astrologers did not;
or
Both the Wise Men and Herods astrologers placed significance on the star and both knew that it meant a new King of the Jews. It should be assumed that Herods astrologers would have prepared regular reports for Herod because that is what they were paid to do, so if they saw anything of any importance (apart from a new king of the Jews) they would have told Herod. Since they didnt tell Herod they must have refrained from telling him about the star out of fear of how he would react.
Note: We can reasonably assume that astrologers elsewhere in the Roman Empire would have likely been in the same situation as Herods were, but we have nothing to indicate Wise Men from the West. So either the star was not visible anywhere west of Judea, or it elicited the same reaction it got from Herods astrologers.
Any other possibilities?
As for the star itself:
It must have been visible for some time- at least long enough for the Wise Men to recognize its significance and make the trip to Judea. If the Wise Men came from no farther away than Mesopotamia, their travel time wouldnt have been very much because of long-established and well-traveled trade routes and the short distance between Mesopotamia and Judea.
It must have been something of a moving star since it seemingly lead the Wise Men to the place where they could find the Christ Child.
It likely was not a comet because in the ancient world comets were seen as harbingers of evil and death, not birth or royalty.
Wise Men:
If the Wise Men came only from Mesopotamia, they likely could have known where a King of the Jews was supposed to be born since the Jews had spent so much time in Mesopotamia during the Babylonian Exile. But, it is hard to believe that anyone who hadnt had some contact with things Jewish would have cared about a new Jewish King. There is some evidence for a Jewish community as far away as India, but I think this settlement was not made until after the birth of Christ.
2. The star was visible to both the Wise Men and Herods astrologers then:
The Wise Men placed significance on the event, but Herods astrologers did not;
or
Both the Wise Men and Herods astrologers placed significance on the star and both knew that it meant a new King of the Jews. It should be assumed that Herods astrologers would have prepared regular reports for Herod because that is what they were paid to do, so if they saw anything of any importance (apart from a new king of the Jews) they would have told Herod. Since they didnt tell Herod they must have refrained from telling him about the star out of fear of how he would react.
Note: We can reasonably assume that astrologers elsewhere in the Roman Empire would have likely been in the same situation as Herods were, but we have nothing to indicate Wise Men from the West. So either the star was not visible anywhere west of Judea, or it elicited the same reaction it got from Herods astrologers.
Any other possibilities?
As for the star itself:
It must have been visible for some time- at least long enough for the Wise Men to recognize its significance and make the trip to Judea. If the Wise Men came from no farther away than Mesopotamia, their travel time wouldnt have been very much because of long-established and well-traveled trade routes and the short distance between Mesopotamia and Judea.
It must have been something of a moving star since it seemingly lead the Wise Men to the place where they could find the Christ Child.
It likely was not a comet because in the ancient world comets were seen as harbingers of evil and death, not birth or royalty.
Wise Men:
If the Wise Men came only from Mesopotamia, they likely could have known where a King of the Jews was supposed to be born since the Jews had spent so much time in Mesopotamia during the Babylonian Exile. But, it is hard to believe that anyone who hadnt had some contact with things Jewish would have cared about a new Jewish King. There is some evidence for a Jewish community as far away as India, but I think this settlement was not made until after the birth of Christ.