“Where is He that is born King of the Jews? For we have seen His star in the East and have come to worship Him.”
There are many explanations about the Lord Jesus's "Star" appearing before or at the time of his body being born on earth by his Mother Mary.
One explanation is the conjunction of the planets that had been observed as early as the mid-19th century by Johannes Kepler saying that the conjunction of Jupiter and Saturn would have been the star of the Nativity.
But one astronomer Roger Sinnott in 1968 had pointed out that the conjunction of a more observable grouping of the planets Venus and Jupiter which had occurred about two years (June 17th 2 B.C) before the Lord Jesus was born.
But the Magis from the east (Babylon) had been observing the skies for so many centuries before and there are many conjunctions of the planets that could have pertained to the Nativity of the the Lord Jesus Christ.
"Then Herod, when he had privily called the wise men, inquired of them diligently what time the star appeared.
King Herod at that time actually had inquired the three Magis on what time did the star had appeared. They could have told them the nearest conjunction of the planets Venus and Jupiter which occurred two years before Jesus was born.
That is why Herod had ordered the Military or soldiers at that time to kill every baby from the ages two years and below.
"Then Herod, ...sent forth and slew all the children who were in Bethlehem and in all the region thereof, from two years old and under, according to the time which he had diligently inquired of the wise men."
It is possible that the three Magis had told Herod that they had seen the star of the Bethlehem two years prior their arrival in Jerusalem causing Herod to order the killing of the babies in that time from the ages of two years and under.
...the star which they saw in the East went before them until it came and stood over where the young Child was.
Here we can read from the Bible that they saw the "star" by the time they would almost arrive where the baby Jesus was and at the time they arrived at his dwelling place.
Could that star be a Supernova explosion that was seen by the Magis before they arrived and while they arrived to Jesus's dwelling place. It could be plausible to say because as we read further the Magis went so joyful after seeing it.
"When they saw the star, they rejoiced with exceeding great joy."
Here we can see that whilst they are already in Jerusalem near arriving to Jesus they saw a star possibly happened at that moment which caused them to maybe jump for joy since they could have concluded already that it was the final sign from heavens that they are looking for aside from what they had observed two years before regarding the planetary conjunctions of Venus and Jupiter (June of 2 B.C).