Bob Moler's Ephemeris Blog

This is Bob Moler with Ephemeris for Tuesday, December 19th. Today the Sun will be up for 8 hours and 48 minutes, setting at 5:04, and it will rise tomorrow at 8:16. The Moon, at first quarter today, will set at 1:06 tomorrow morning.

This year Jupiter is our bright evening Christmas star. But what about the one described in the Bible, in the Gospel of Matthew? We will look today at the first of two events that may have been recorded as the Star of Bethlehem. In 7 BC there was a rare event over 8 months when three times the planet Jupiter passed Saturn against the stars of the constellation Pisces. Could the Persian astrologer priests called Magi, have read into the event enough significance to start the journey to Jerusalem in search of the newborn King of the Jews? It was the scribe’s readings that then sent them to Bethlehem. It is thought that Pisces was associated with the Hebrews, Jupiter with the Messiah or world ruler, and Saturn with the peoples of Palestine.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EST, UT –5 hours). They may be different for your location.

Addendum

The normal motion of the sun, moon and planets in the sky is to the east, or to the left in this diagram. Jupiter takes a bit less than 12 years to orbit the sun while Saturn takes a bit less than 30 years, so Jupiter will pass Saturn about every 20 years. However, when they are both at opposition of the sun when they do that and closest to the earth, they will appear to move backwards for a time. This is called retrograde motion from their normal eastward motion. Jupiter being closest to us and closer to the Earth’s speed makes a bigger retrograde loop than Saturn does. So when they’re both at opposition when they cross paths we get a triple conjunction like this.