12/24/2020 – Ephemeris – Was the Star of Bethlehem a triple conjunction of Jupiter and Saturn in 7 BC?

This is Bob Moler with Ephemeris for Christmas Eve, Thursday, December 24th. Today the Sun will be up for 8 hours and 48 minutes, setting at 5:07, and it will rise tomorrow at 8:18. The Moon, 3 days past first quarter, will set at 3:50 tomorrow morning.

For many years the most popular theory for the origin of the Star of Bethlehem was a triple conjunction of Jupiter and Saturn in 7 BC. This is because, due to Earth’s motion, other planets from our view point seem to reverse course when we pass them or are being passed in the circular racetrack of the solar system. When Jupiter and Saturn approach each other just before they go retrograde or reverse course they have a chance to pass each other, backup and pass again, then going forward to pass a third time. Jupiter and Saturn did that last in 1981, so it’s a reasonably rare occurrence, especially when it happens in front of the constellation Pisces which was supposedly related to the Jews.

The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Jupiter and Saturn pass each other three times from May to December in 7 BC against the constellation of Pisces. Reload the page to replay the animation. Created using Cartes du Ciel (Sky Charts) and GIMP.

Retrograde motion illustrated using Mars in 2018. Created using my LookingUp program.

 

 

12/19/2017 – Ephemeris – Were celestial events in 7 BC interpreted as the Star of Bethlehem?

Ephemeris for Tuesday, December 19th. The Sun will rise at 8:15. It’ll be up for 8 hours and 49 minutes, setting at 5:04. The Moon, 1 day past new, will set at 6:34 this evening.

This year we have no bright evening Christmas star. But what about the one described in the Bible, in the gospel of Luke? 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 6 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 new born 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 times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

The Jupiter-Saturn triple conjunction of 7 BC. Click on the image to enlarge. Created using Cartes du Ciel.

The animation above shows the planets at 5 day intervals in 7 and a bit in 6 BC.  The normal or posigrade motion is toward the east or left.  When an outer planet approaches its opposition from the Sun, it seems to slow and reverse direction and head westward for a time, which is retrograde motion.  After a time it reverses and heads back eastward again.  That’s why the planets seem to see-saw back and forth.  Jupiter passes Saturn every 20 years.  The next time will be in 2020.  On my Wednesday planet charts Jupiter is seen sneaking up on Saturn week by week.  In order to have three conjunctions instead of one, the planets need to be near opposition from the Sun when they pass.  The last time that happened was in 1980, but it wasn’t against Pisces.  Triple conjunctions against a particular zodiacal constellation are much rarer.

The dates for key events in the animation above are:

• First Conjunction May 29, 7 BC
• Planets are Stationary July 6, and begin retrograde motion
• Second Conjunction October 11
• Planets are Stationary November 1 and resume posigrade motion
• Third Conjunction on December 8
• Mars joins February 26, 6 BC

Retrograde motion was difficult to explain when one thinks that the Earth is the center of the Universe and stationary, while the planets supposedly orbited in perfect uniform circular motion around it.  It’s easy when the Earth is a moving planet like the rest.  When an outer (superior) planet is at opposition from the Sun.  The Earth is between the Sun and planet and moving faster.  So we’re passing the outer planet.  When you are in a car passing another, the car being passed seems to move backward with respect to your car.  Since the planets orbits are like a race track, we get to lap the outer planets at regular intervals.

12/22/2016 – Ephemeris – Could Jupiter and Saturn have combined to be the Star of Bethlehem?

Ephemeris for Thursday, December 22nd.  The Sun will rise at 8:17.  It’ll be up for 8 hours and 48 minutes, setting at 5:05.  The Moon, 2 days past last quarter, will rise at 2:45 tomorrow morning.

This morning the planet Jupiter is seen right below the waning crescent Moon.  It reminds me of one of the possible answers to the questions to what the Star of Bethlehem was.  Back in 7 BC Jupiter passed Saturn three times in that year.  This is a reasonably rare occurrence especially against a particular constellation, which in this case was Pisces the fish, which would occur every 800 plus years.  Early in the run of this program there was another so-called triple conjunction of Jupiter and Saturn.  This time it was against the constellation of Virgo the virgin in 1980 and 81.  Jupiter passes Saturn every 20 years, but only when it does so when they are opposite the Sun in the sky is there a chance for a triple conjunction.  Tomorrow I’ll look at two really close conjunctions of Jupiter and Venus that also could have been seen by the Magi as the Star of Bethlehem.

Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Jupiter and the Moon at 7 a.m. this morning, December 22, 2016. Created using Stellarium.

Jupiter and Saturn pass each other three times from May to December in 7 BC. Created using Cartes du Ciel (Sky Charts) and GIMP.  Click image to enlarge.