12/19/2022 – Ephemeris – Hunting for the Star of Bethlehem: What it wasn’t

This is Ephemeris for Monday, 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, 3 days past last quarter, will rise at 4:59 tomorrow morning.

In these last days before Christmas, I’d like to explore what in the sky could have been the Star of Bethlehem from an astronomical point of view. If it had to do with the arrangement of planets, tracing back two thousand years would be simple. If it was some sudden appearance of an actual star or comet, we would have to rely on contemporary accounts. Those would have to come from the Chinese and Koreans. The state of astronomy around the Mediterranean and the Middle East was pretty stagnant due to the fact that they thought that the heavens were perfect and changeless, so things like comets and novae or “New Stars” meant change, so were not really part of the heavens. So we must look for something more mundane.

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

Probably the first person to kick off the search for the Star of Bethlehem was Johannes Kepler. (These are slides from this year’s Searching for the Star of Bethlehem presentation I gave to the Grand Traverse Astronomical Society. The captions are from the text of the presentation)

The search for the Star really started with Johannes Kepler, who lived from 1571 to 1630. He was an astronomer, although he cast horoscopes for the odd prince or duke, which is how he made a living. His mother was even charged for being a witch, but nothing came of it. And after much trial and error discovered his Three Laws of Planetary Motion. His story is a fascinating one.

Kepler also discovered a supernova, the last one seen in the Milky Way. This is an old star chart that records Kepler’s Star,
a supernova, or super bright new star, he discovered on October 9, 1604. I colored it yellow and have an arrow pointed to it, in Ophiuchus’ right ankle.

Here is a Stellarium recreation of the sky the night of his discovery. It’s the southwestern sky near the end of evening twilight, October 9, 1604, the night Kepler discovered the supernova that bears his name. It got him to thinking, could a similar grouping of a nova and planets be the Star of Bethlehem?
He knew of no nova being reported back then, though no one in the western world probably would have. That would be a change in the officially changeless heavens, so it couldn’t possibly have been a real heavenly object. And being the mathematical genius he was, (he did discover the Three Laws of Planetary Motion), found a very interesting conjunction of Jupiter and Saturn, with Mars piling on later, that occurred in 7 BCE. (Click on the image to enlarge it.)

02/10/2015 – Ephemeris – Orion’s bright red star, Betelgeuse

Ephemeris for Tuesday, February 10th.  The sun will rise at 7:50.  It’ll be up for 10 hours and 13 minutes, setting at 6:03.   The moon, 1 day before last quarter, will rise at 12:51 tomorrow morning.

The bright red star in constellation Orion’s shoulder is Betelgeuse, and its now thought to be about 640 light years away give or take a couple of hundred light years*.  The name Betelgeuse means “Armpit of the central one” in Arabic.  Orion is seen in the south at 9 in the evening.  Even at Betelgeuse’ great distance it’s the star whose surface is easiest seen, after the sun of course.  That’s because it’s so big.  As large around as the size of the orbit of Jupiter.  Betelgeuse is losing mass in a huge cloud around it.  It is a massive star in the late stages of its life even though it’s only 7 million years old. Some astronomers speculate that it will explode in a massive supernova within the next million years.

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

Update

* I’m being a bit facetious here. See the addendum, and also by coincidence a post from EarthSky today How far is Betelgeuse?

Addendum

Orion upright and due south. Created using Stellarium.

Our estimates of the size, mass and luminosity of Betelgeuse depend on knowing its distance.  The distance is not well-known because Betelgeuse is a single star, it is not a binary for which can be applied Newton’s laws to calculate these values.  Therefore these values in the broadcast program, where I have 59 seconds total, appear more certain than they really are.  Wait for Thursday’s program when I cover Rigel and see how close the values are between the two.  But Rigel appears to be a different star altogether.  Somebody’s wrong.

“This artist’s impression shows the supergiant star Betelgeuse as it was revealed thanks to different state-of-the-art techniques on ESO’s Very Large Telescope, which allowed two independent teams of astronomers to obtain the sharpest ever views of the supergiant star Betelgeuse. They show that the star has a vast plume of gas almost as large as our Solar System and a gigantic bubble boiling on its surface. These discoveries provide important clues to help explain how these mammoths shed material at such a tremendous rate. The scale in units of the radius of Betelgeuse as well as a comparison with the Solar System is also provided.” Credit: ESO/L. Calçada (ESO is the European Southern Observatory)

09/13/11 – Ephemeris – Supernova in the Pinwheel Galaxy

Tuesday, September 13th.  The sun will rise at 7:18.  It’ll be up for 12 hours and 38 minutes, setting at 7:57.   The moon, 1 day past full, will rise at 8:05 this evening.

There is currently a supernova in a galaxy near the handle of the Big Dipper.  The bright moon is interfering with its visibility in telescopes.  It’s in a galaxy called M101 or the Pinwheel galaxy, a difficult to spot galaxy between and above the two end stars of the handle of the Big Dipper.  The galaxy is 21 million light years away, relatively close as galaxies go.  It is being intensely studied because it is of a type, 1a, that is used for distance measurements of far more distance galaxies.  This kind of Supernova is thought to be the destruction of a white dwarf star in a close binary relation with a more massive star and is drawing matter off the larger star.  When the dwarf reaches 1.38 times the sun’s mass…  Kablooey!  Astronomers are trying to see if that’s true for this star.

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

06/16/11 – Ephemeris – Supernova in the Whirlpool Galaxy

Thursday, June 16th.  Today the sun will be up for 15 hours and 33 minutes, setting at 9:29.   The moon, 1 day past full, will rise at 10:23 this evening.  Tomorrow the sun will rise at 5:56.

One of the coolest galaxies visible in a telescope is the Whirlpool Galaxy, also known as M51, near the handle of the Big Dipper.  With a large enough amateur telescope, the spiral pattern can just be glimpsed.  Usually it takes long exposure photographs to reveal the spiral structures of the galaxies that have them.  A few weeks ago a supernova appeared in the outer spiral arm of the Whirlpool galaxy, visible in medium size telescopes of 8 inch diameter and up.  Based on the study of the light given off by the supernova it appears that this is was a massive star whose core collapsed allowing the rest of the star to explode briefly making the star billions of times brighter than the sun.  The supernova will gradually fade in an expanding cloud of gas.

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