Believers may assert that Jesus was born under an auspicious astrological sign.
But skeptic says: Well, there was a rare conjunction of the planets in 7 BC. It was around the time Jesus was supposed to have been an infant. Soon after the conjunction--it involved Jupiter and Saturn--Jupiter went into retrograde motion. It's an optical illusion, actually. So the planet moved backwards and passed Saturn again.
Jupiter resumed forward motion, so it passed Saturn a couple months later again, and so there were three passes.
The conjunctions were in Pisces the Fish. Astrologers may say the triple pass had special significance for Israel since Pisces was its zodiacal sign. The list given below gives the rarity of triple Jupiter and Saturn conjunctions in Pisces
980-979 BC Pisces
861-860 BC Pisces
821-820 BC Leo
563-562 BC Taurus
523-520 BC Virgo
146-145 BC Cancer
7 BC Pisces
Other evidence suggests that Pisces was Israel's sign but only after AD 300. The author Michael Molnar drives this claim, saying Aries the Ram was the sign of Israel before AD 300. He says Jupiter, Saturn, and the moon were in Aries in 6 BC, and it was the portent for the infant Jesus (The Star of Bethlehem: The Legacy of the Magi, Michael R. Molnar). But in order to see it, the observer had to stare towards the rising sun--ouch, my eyes.
The sign happens about every 60 years, but this time Mars went through it, which bode well, too.
The catch was, there was a portent for nearly each year from 11 BC to AD 1. One year there was a comet, the following year a planetary conjunction, next a nova, and so forth. I say the author of Matthew had heard reports of several astrological signs and had trouble choosing one. So he wrote an ambiguous story about a miracle star and described it just a little bit and when it appeared.
Recap: Christians may believe that a conjunction was the portent for the nativity of Jesus. But there was a variety of signs, which might not have had anything to do with his birth.