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Geek’s Guide to Tracking the Bethlehem Star

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Introduction

Have you heard about this? www.bethlehemstar.net presents a well-researched case pointing to some intriguing astronomical signs which could be the very ones that motivated the wise men to travel to Jerusalem and then to Bethlehem around the time of Jesus’ birth. The really cool thing is, using readily available planetarium software that mathematically models the stars and solar system, these signs can readily be reproduced and verified. In brief what can be seen is this:

  1. Conjunction of the planet Jupiter with the star Regulus in Sept of 3BC
    This conjunction begins on the very first day of the Hebrew new year.
  2. A second conjunction of Jupiter with Regulus in Feb of 2BC
  3. A third conjunction of Jupiter with Regulus in May of 2BC
  4. A very full conjunction of Jupiter with the planet Venus in June of 2BC
    This is 280 days, or precisely 40 weeks, after Jupiter’s initial conjunction with Regulus.
  5. Jupiter’s reappearance later in the year moving away from Regulus toward Virgo, and toward the end of December coming to a stop and reversing its course.

These things also tie into some signs in the sky that were seen at the time of Jesus’ crucifixion. Though I haven’t covered this here, it is well worth investigating and is described in detail at the BethlehemStar.net website.

For those of you who are investigative types, following this introduction is a “Geek’s guide” to enable you to see these things for yourself and maybe begin some investigation of your own.

The Bethlehem Star

I don’t know where the wise men were from, but a theory that makes sense is that they were from Babylon, and had some clues about what to watch for that had been passed down to them from the time of Daniel. The first conjunction’s commencing right on the first day of the Hebrew new year may have been a significant sign to them. This happened as Virgo was rising with the sun, with a crown of 12 stars on her head, and just as the new moon appeared at her feet (see Rev 12:1) The twelve stars may refer to the constellation Leo which has 9-15 stars, depending on which ones are considered bright enough to count. Regulus is one of these stars of Leo – the brightest one.

Two times that year the conjunction was repeated. Not so fully as the first – more like just an echo of the first conjunction, maybe helping to confirm it as being the long-awaited sign. And finally comes the bright conjunction of Jupiter with Venus, lasting just one evening in June of 2BC. BethlehemStar.net proposes the first conjunction in September as marking the time of Jesus’ conception, with the conjunction in June marking his birth. We’ll see in other research that the year 3/2 BC is quite well attested as the actual year of Jesus’ birth – and though this isn’t the only theory which places Jesus’ birth in this year of 3/2 BC, this one does seem worth considering. I’ve been told that the typical time span from conception to birth is 40 weeks. Counting the days inclusively (meaning that both the starting and ending days are counted) from the first day of the Hebrew New Year to the June 17 conjunction, we get 280 days, or precisely 40 weeks.

If you’d like to check the math yourself, go to torahcalendar.com to see that the first day of that Hebrew New Year (Hebrew month 7 in 3BC) corresponds to our Sept 11-12. For the ending date, note that the June 17 conjunction happens after sunset of the 17th, so actually occurs on the Hebrew day corresponding to June 17-18 of our present-day calendar. Be sure to count just 28 days for February of 2BC, and then following the usual Hebrew method of counting days, count full days for both the starting and ending points. A handy way to quickly do the inclusive count is to just “subtract” Sep 11, 2010 from Jun 18, 2011 in a spreadsheet. I picked 2010-2011 because my spreadsheet program doesn’t handle dates as old as 3-2BC. But any non-leap year should give the same answer. To see the answer “280”, you’ll probably also need to manually format the result to be just an ordinary number rather than a date.

Having seen these signs, the wise men took it as a clear sign of the birth of a Jewish king, and came to check it out in person (Matthew 2:1-12). The star didn’t exactly lead them there. They had to stop for directions in Jerusalem, and learned from the Old Testament writings there that Bethlehem was the place to look. But they said that they’d seen his star in the east. What star would this be? A good guess is the planet Jupiter, since that was the common thread in the conjunctions they had probably seen from Babylon.

But Jupiter kind of disappears for a while after its June conjunction with Venus. By the middle of August it’s rising and setting with the Sun, making it pretty hard to locate. It isn’t until September that it begins to be visible again just before sunrise. As the days go by it rises earlier and earlier, each day getting a little higher in the sky before being washed out by the rising Sun. By the end of November it’s reaching its full height in the sky by dawn, at which time its position is due South from Jerusalem. This continues through December and into the next month as well, each day rising a bit earlier, and reaching its highest point in the sky when it’s due south from Jerusalem. So the star at its highest point would have been in front of the wise men, if they were making the trip to Bethlehem during this time.

As far as its position with respect to the stars, all this time Jupiter has been moving toward Virgo – initially out of reach of her outstretched hand, then at her hand, then at her forearm, then at her elbow about the middle of November. But Jupiter is slowing down, and reverses direction toward the end of December, returning to Virgo’s elbow by mid-February. So there’s a point at which Jupiter is almost stationary with respect to the stars, halfway between mid-November and mid-February, around the end of December, when it’s reversing direction at Virgo’s upper arm.

This seems to fit reasonably well with the description in Matthew 2:9-10. By the time the wise men had finished conferring with Herod and the chief priests in Jerusalem, the star had made its reappearance and “…they went on their way, and the star they had seen in the east went ahead of them until it stopped over the place where the child was. When they saw the star, they were overjoyed.”

Another way to understand these things would be to take them as something supernatural that God did, maybe just having an angel lead the way to Bethlehem by means of a star-like light. God could surely have done that. That way he could even have led them right to the particular house where Mary and Joseph were staying. A real star or planet wouldn’t have been able to guide them that specifically. But the wise men saw it as a star, and identified it as the same one they had previously seen from Babylon. So it seems likely that it was indeed Jupiter, and that the wise men used some more ordinary means to locate the particular house they were looking for, just as they had done in Jerusalem.

If this is the correct explanation of the events, just think what this says about our God. It means that He had all these times and events clearly in mind when He first set the planets in their orbits. It’s almost overwhelming to think of the fullness and completeness of His knowledge and understanding. He is fully capable of setting every detail carefully in place just as it needs to be. And it gives me great comfort to realize that this is the same One who has my life in His hands. “You know when I sit and when I rise; you perceive my thoughts from afar” (Psalm 139:2). There’s no one else in the entire universe so fully able and trustworthy to take me by the hand, to provide my daily bread, and to show me each step He has for me to take.

The Geek’s Guide

How to see these things for yourself.

If you already have a planetarium program that you like, you can probably just use that. If not, a number of free planetarium programs are available for download. The one that I’ve tried is called Stellarium. It has versions for Linux, Mac, and Windows, and has done the job nicely. Here are the steps I followed to install and use it on a Windows system:

Download Stellarium

Download the Stellarium program from www.stellarium.org

Install it

Run “stellarium-0.12.4-win32.exe” to install it.

Run it

Find the new “Stellarium” shortcut on your Start Menu and use it to start the program. Initially, by default, the program shows you the sky looking south from Paris at the current time and date.

Set the Time Zone

The two locations of interest will be Babylon in the time zone GMT+3, from where the wise men probably first saw the star, and Jerusalem in the time zone GMT+2, near their final destination of Bethlehem. We’ll take care of this time zone detail first because it requires a restart of the Stellarium program.

By default the Stellarium program shows times according to the time zone that’s set for your computer clock. But for our purposes it would be more helpful to see times that correspond to the time zone of the chosen viewing location. This can be accomplished by manual adjustment. To adjust Stellarium to use Babylon’s time zone, drag the mouse to the lower left side of the screen and select the fifth from the top icon. This opens the “Configuration window”. In this “Configuration” window:

  • Click on the “Plugins” tab
  • Select the “Time Zone” plugin
  • Under Options, click the “configure” button
    • Make sure the “Time zone” tab is showing
    • Choose “Offset from UTC: 3.00 hours”
    • Save settings
    • Close the “Time Zone” window using the X in the upper right corner
  • In the Configuration window click on (x) Load at startup
  • Close the “Configuration” window using the X in the upper right corner
  • Close and restart the Stellarium program

Now sunrise and sunset should occur at the proper times from Babylon’s perspective. The time zone for Jerusalem can be set in the same way, but using 2.00 hours for the offset from UTC.

Set the Location

Drag the mouse to the lower left side of the screen and select the top icon that appears. This opens the “Location window”, from which a different Location can be chosen. You’ll see a list of location names on the upper right side of the window, and just beneath the list of names, next to the little magnifying glass, you’ll see a place to type in a name. We can see from en.wikipedia.org/wiki/Babylon that the remains of the city of Babylon are found in present-day “Al Hillah”. So next to the magnifying glass, start typing “al-hillah”, and when you see “al-Hillah, Iraq” appear in the list of names, click on it. This location is now selected, and its latitude, longitude, and altitude are automatically filled in from the info in Stellarium’s location database.

Set the Direction that you’re facing

You’re now looking South from Babylon at the current time and date. You can tell it’s south by the red “S” in the middle of the screen. We first want to take a look at the stars as they rise in the East from Babylon’s perspective. As we face South that would be to our left, so to rotate in that direction, click on the scenery near the left side of the screen and drag it to the right. You should soon see a red “E”. In order to look due East, drag until that’s at the center of the screen.

Set the date and time

We’re now looking east from Babylon, but still seeing the sky of 2012. Again drag the mouse to the lower left side of the screen, and this time select the 2nd to top icon that appears. This opens the “Date/time” window. Initially it shows the current year, 2012 AD.

Another thing to be aware of in this program is that though it tracks fine all the way back to the year 1 AD, it’s not designed with BC dates in mind. You can get there, by using negative numbers for the year, but you need to be aware that the BC/AD calendar system doesn’t include a year zero, while the astronomical years of Stellarium do. So to reach the year 3BC with the Stellarium program, you need to use -2 as the year.

Let’s start looking on Sept 1 of 3BC:

  • Select the year (probably 2012 by default) and type “2” to replace it
  • Put a minus sign in front of it to make the year -2
  • Select the month and type “9” to replace it(or just use the up/down arrows to get to month 9)
  • Select the day and type “1” to replace it(or just use the up/down arrows to get to day 1)
  • Select the hour and type “18” to replace it(or just use the up/down arrows to get to hour 18:00)

This should be about the beginning of night time, at 6pm. By default the time continually advances just as a clock does, but you can make it hold still. Drag the mouse to the bottom edge of the screen, on the left end. Near the right end of the toolbar that appears, you’ll see arrows that look like the rewind, play, and fast forward buttons of a CD player. Click on the one that looks like a “play” button, the single right-pointing arrow, and that will make time stop advancing. Now it looks like a “pause” button. Clicking again on it will make time start advancing again. But just leave it off so you can have full manual control of the time.

If you need to close the “Date and Time” Window, that can be done by clicking the “X” in its upper right corner. But for convenience, just leave it open. Click on the title bar where it says “Date and Time” and just drag it to an out-of-the-way place like maybe the upper right corner of the screen.

Label the stars and constellations

You should now see lots of stars. But unless you know astronomy really well you won’t know exactly what stars you’re looking at. We need to be able to readily identify them by name.

  • Drag the mouse to the bottom edge of the screen, on the left end.
  • Click the first icon on the left to turn on Constellation lines
  • Click the second icon from the left to turn on Constellation labels

“Planet labels” is on by default, but in case you need to turn this on or off, it’s the tenth icon from the left. Going to the “Date and Time” window again, click on the hour and use the up arrow to start stepping into the night hour by hour. The constellations are nicely identified. A few stars and planets are labeled, but not all – only the brightest ones. When you reach about 4:00am you should see Jupiter and the constellation Leo having just risen in the east. One of the stars making up the constellation Leo is Regulus, but it’s probably not yet labeled. This is a good time to adjust that. Drag the mouse to the lower left side of the screen and when the icons appear, select the 3rd one from the top. In the “View” window that comes up, make sure the “Sky” tab is selected, and under “Labels and Markers”, click on the slider for “Stars” and drag it to the right, watching its effect on the star labels. Near Jupiter you should soon see the label for Regulus appear. With the slider all the way to the right, the screen will be packed with way too much information. So back it off to where just Regulus and several other stars of the constellation Leo are labeled. Notice there’s a similar slider here for planets. The default setting has worked fine so far for me, but this is where that would be adjusted. When finished with these settings, click the “X” in the upper right corner of the “View” window to close it.

Step through time and watch for the first conjunction

Notice that Jupiter is already quite close to Regulus. This is because we’re beginning to watch just a week or two before the conjunction. To get a feel for what the sky is looking like on this date, start out by stepping through hour by hour. Notice that all the stars and planets rise in the east. You’ll see Virgo rise “clothed with the sun”, meaning that the constellation is rising at sunrise. This happens during this particular time period every year. Keep stepping through the days and nights an hour at a time, and pay attention to what the moon is doing. By Sept 6, Jupiter has gotten a bit closer to Regulus, and the moon is in conjunction with Jupiter. Note that Virgo is still rising with the sun. Keep stepping through an hour at a time, watching both Jupiter and the moon. By Sept 11-12, the moon is at Virgo’s feet, and Jupiter’s conjunction with Regulus is beginning. By the next night the moon has moved on, but Jupiter’s conjunction with Regulus continues, getting very close by Sept 15.

Now focusing in on just Regulus and Jupiter, use the up/down arrows on the day of the month to try stepping through time one day at a time. Scanning from the 11th to the 18th and back, it seems that that’s about the extent of the conjunction, with the closest approach on Sept 14 or 15. The first apparent full contact is Sept 12 at about 2am, on the first day of the Hebrew new year, 1 Tishri.

Continue stepping through time to see the 2nd and 3rd conjunctions

This day-at-a-time scanning is pretty nice. It gives you a good feel for the path Jupiter is taking. The next conjunction isn’t until February, but you can scan through a day at a time to get a better feel for Jupiter’s path. An additional technique that can make it easier to track a particular star or planet is to use a search. This will keep the object of interest in the center of the screen as you step through time. To do this:

  • Drag the mouse to the lower left side of the screen and select the fourth icon from the top
  • This opens the “Search window”
  • In the “Find Object” dialog box, type “jupiter” and press “Enter”

As you investigate, watch for the following events:

Facing east from Babylon

  • 3BC Sep 12 Virgo rises with the sun, with the moon at her feet.
    (-2-09-12 in Stellarium program)
  • 3BC Sep 15 +/- 4 First conjunction of Jupiter with Regulus.
    (-2-09-15 in Stellarium program)
    It rises in the east about 2am Babylon time
  • 2BC Feb 16 +/- 4 Second conjunction of Jupiter with Regulus.
    (-1-02-16 in Stellarium program)
    It’s already high in the eastern sky at dusk

Facing west from Babylon

  • 2BC Feb 17 +/- 4 Second conjunction of Jupiter with Regulus.
    (-1-02-17 in Stellarium program)
    It sets in the west about 5:30am Babylon time
  • 2BC May 9 +/- 4 Third conjunction of Jupiter with Regulus.
    (-1-05-09 in Stellarium program)
    It sets in the west just after midnight Babylon time
  • 2BC Jun 17 Dead-on conjunction of Jupiter with Venus.
    (-1-06-17 in Stellarium program)
    Visible at sunset; 25 degrees at 8pm, 12 degrees at 9pm, setting in the west about 10pm Babylon time

Jupiter now gets very hard to spot because it’s rising and setting with the sun. About Aug 17 it’s almost in conjunction with the sun. By about the beginning of September, it begins to precede the sun enough in its rising to begin to be visible in the east at dawn from Babylon. This explains why the wise men lost sight of the star for a while. In Sep, Oct, and Nov, Jupiter becomes quite visible in the east around 5am Babylon time, now getting farther and farther from Regulus and approaching Virgo. Roughly the same thing can be seen from Jerusalem. But Jupiter is slowing down, getting ready to reverse direction again.

Watching the star from Jerusalem

By now the wise men have surely reached Jerusalem, so let’s change the time zone and location to better match what they would have seen.

Time Zone

Drag the mouse to the lower left side of the screen and select the fifth from the top icon. This opens the “Configuration window”. In this “Configuration” window:

  • Click on the “Plugins” tab
  • Select the “Time Zone” plugin
  • Under Options, click the “configure” button
    • Make sure the “Time zone” tab is showing
    • Choose “Offset from UTC: 2.00 hours”
    • Save settings
    • Close the “Time Zone” window using the X in the upper right corner
  • In the Configuration window “Load at startup” should still be checked
  • Close the “Configuration” window using the X in the upper right corner
  • Close and restart the Stellarium program

Sunrise and sunset should now occur at the proper times from Jerusalem’s perspective.

Location

Drag the mouse to the lower left side of the screen and select the top icon that appears. This opens the “Location window”, from which a different Location can be chosen. Just as for Babylon, Stellarium already has the needed location data for Jerusalem, but you need to know how Stellarium spells this name in order to find it. The cursor should already be in the search window next to the magnifying glass. Begin typing “yerushalayim”, and when it appears in the list, click on it to select it. You should now see the red arrow on the world map pointing at the approximate location of Jerusalem. Close the “Location” window using the X in the upper right corner.

Date and time

Drag the mouse to the lower left side of the screen, and select the 2nd to top icon that appears. This opens the “Date/time” window. Let’s go to Sept 1 of 2BC:

  • Select the year (probably 2012 by default) and type “1” to replace it
  • Put a minus sign in front of it to make the year -1
  • Select the month and type “9” to replace it(or just use the up/down arrows to get to month 9)
  • Select the day and type “1” to replace it(or just use the up/down arrows to get to day 1)
  • Select the hour and type “1” to replace it(or just use the up/down arrows to get to hour 01:00)

This will be the middle of the night, at 1am. Turn off the clock so you can have full manual control of the time. Drag the mouse to the bottom edge of the screen, on the left end. Near the right end of the toolbar that appears, click on the arrow that looks like a “play” button, the single right-pointing arrow, to make time stop advancing.

Search

At this point what we’re interested in is following all that Jupiter does. To keep Jupiter in the center of the screen as we step through time:

  • Drag the mouse to the lower left side of the screen and select the fourth icon from the top
  • This opens the “Search window”
  • In the “Find Object” dialog box, type “jupiter” and press “Enter”

Looking below the Horizon

At first we don’t see anything because Jupiter is below the horizon. But stepping forward in time, Jupiter should be seen rising in the East about 4:20am. We can look below the horizon as follows:

  • Drag the mouse to the left end of the bottom edge of the screen
  • Click on the 6th icon from the left

Now we can see that Virgo is about to rise, with Jupiter just out of reach of her outstretched hand. Continuing to step forward in time, by 4:50 we see Jupiter begin to fade in the brightness of the sunrise. At this point Jupiter is just beginning to reappear, and doesn’t stay visible for very long.

Azimuthal Grid

An interesting detail to begin watching during this period is where exactly is Jupiter each night when it reaches its highest point. This is a good time to try out another feature of the program, the “Azimuthal Grid”:

  • Drag the mouse to the bottom edge of the screen, on the left end.
  • Click the fifth icon from the left to turn on the Azimuthal grid

Now the altitude in degrees above the horizon can be readily read from the grid.

Tracking Jupiter

The most significant points in the Hebrew calendar are the new moon marking the beginning of a month, and the full moon in the middle of each month. So starting when Jupiter first reappears, here’s what we find it doing at or near each of these points:

  • 2BC Sep 1 (1 Tishri) New moon.
    (-1-09-01 in Stellarium program)
    Jupiter out of Virgo’s reach
    Rises at 4:20am
  • 2BC Sep 14 (14 Tishri) Full moon.
    (-1-09-14 in Stellarium program)
    Jupiter at Virgo’s hand
    Rises at 3:42am. Reaches 17 degrees altitude by dawn
  • 2BC Oct 1 (1 Heshvan) New moon.
    (-1-10-01 in Stellarium program)
    Jupiter at Virgo’s forearm
    Rises at 2:51am. Reaches 30 degrees altitude by dawn
  • 2BC Oct 13 (13 Heshvan)
    (-1-10-13 in Stellarium program)
    Jupiter and Venus at Virgo’s forearm
    Rise together at 2:15am
  • 2BC Oct 14 (14 Heshvan)
    Full moon (-1-10-14 in Stellarium program)
    Jupiter and Venus at Virgo’s forearm
    Rise not quite together at 2:12am. Reach 41 degrees altitude by dawn
  • 2BC Oct 31 (1 Kislev) New moon.
    (-1-10-31 in Stellarium program)
    Jupiter approaching Virgo’s elbow
    Rises at 1:18am. Reaches 55 degrees altitude by dawn
  • 2BC Nov 13 (14 Kislev) Full moon.
    (-1-11-13 in Stellarium program)
    Jupiter in conjunction with Zaniah at Virgo’s elbow
    Rises 12:36am. Reaches 64 degrees by dawn
  • 2BC Nov 29-30 (1 Tevet) New moon.
    (-1-11-29 in Stellarium program)
    Jupiter at Virgo’s upper arm
    Rises at 11:37pm. Due south at 68 degrees, 5:58am
  • 2BC Dec 11-12 (13 Tevet) Full moon.
    (-1-12-11 in Stellarium program)
    Jupiter at Virgo’s upper arm
    Rises at 10:54pm. Due south at 68 degrees, 5:14am
  • 2BC Dec 27-28 (29 Tevat)
    (-1-12-27 in Stellarium program)
    Jupiter at the center of its reversal, probably its most stationary point
    Rises at 9:53pm. Due south at 68 degrees, 4:12am
  • 2BC Dec 28-29 (1 Shevat) New moon.
    (-1-12-28 in Stellarium program)
    Jupiter at Virgo’s upper arm
    Rises at 9:49pm. Due south at 68 degrees, 4:09am
  • 1BC Jan 9-10 (13 Shevat) Full moon.
    (0-01-09 in Stellarium program)
    Jupiter at Virgo’s upper arm
    Rises at 9:01pm. Due south at 68 degrees, 3:20am
  • 1BC Jan 27-28 (1 Adar I) New moon.
    (0-01-27 in Stellarium program)
    Jupiter at Virgo’s upper arm, returning to her elbow
    Rises at 7:44pm. Due south at 68 degrees, 2:05am
  • 1BC Feb 8-9 (13 Adar I) Full moon.
    (0-02-08 in Stellarium program)
    Jupiter at Virgo’s upper arm, almost at her elbow
    Rises at 6:51pm. Due south at 68 degrees, 1:13am
  • 1BC Feb 9-10 (14 Adar I)
    (0-02-09 in Stellarium program)
    Jupiter in conjunction with Zaniah at the elbow of Virgo
    Rises with the moon at 6:47pm. Due south at 68 degrees, 1:09am
  • 1BC Feb 10-11 (15 Adar I)
    (0-02-10 in Stellarium program)
    Jupiter in closest conjunction with Zaniah at the elbow of Virgo
    Rises at 6:42pm. Due south at 68 degrees, 1:05am
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2 Comments

  1. […] 3 times during his ministry. So was he 33 when he died? Taking his birth date as June 17, 2BC (see previous Geek’s Guide), at first glance it seems unlikely. But remembering that there’s no year zero and doing the […]

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  2. […] Geek’s Guide t… on Geek’s Guide to Tracking… […]

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