THE SOUTHWORTH PLANETARIUM
207-780-4249 www.usm.maine.edu/planet
70 Falmouth Street Portland, Maine 04103
43.6667° N 70.2667° W
Founded January 1970
Julian date: 2457740.16
"I demonstrate by means of philosophy that the earth is round, and is
inhabited on all sides; that it is insignificantly small, and is borne
through the stars."
-Johannes Kepler
THE DAILY ASTRONOMER
Tuesday, December 20, 2016
Christmas Star Astronomy
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"Astronomy of the Christmas Star"
The title of the next episode of "Radio Astronomy,"
airing on WMPG 90.9 FM (www.wmpg,org)
at 1:00 p.m. Friday, December 23.
Lutheran pastor Maria Anderson-Lippert is our
special guest as we delve into the astronomical
aspects of the Star of Bethlehem.
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The Christmas Star, better known as the "Star of Bethlehem," has intrigued
many astronomers for centuries. Many of them have developed theories
attempting to explain the "star" that guided the three Zoroastrians to
Bethlehem, birthplace of Jesus. If the star had actually been a
naturally occurring celestial event -an issue that shall remain forever
unresolved- what might it have been? The matter is debated and discussed
even today in the early 21st century, despite the protestations of some
astronomers who not only consider the problem to be unsolvable, but also
worry that these inquiries might offend certain religious sensibilities.
These understandable misgivings notwithstanding, we shall proceed to
summarize and briefly discuss three of the most common theories.
*Could the Magi have followed a comet?*
*Comet McNaught during its 2006 visitation to the inner*
*solar system.*
Comets are icy interlopers from the outer solar system. During most of
their journey toward and away from the Sun, they are dark and therefore
invisible. When a comet approaches the inner solar system, the Sun's
heat melts some of the surface ice, creating a luminescent tail that can
sometimes stretch over a million miles. If the comet is sufficiently
bright and large, it can produce quite a spectacle in the sky. (One
might think of the 1996 appearance of the massive long period Comet
Hyakutake.) Such a sight would certainly have attracted the attention of
sky-admiring Zoroastrians. A comet can also remain visible for weeks,
providing the Magi with ample time to travel to the region toward which
they were being guided.
However, the star was said to have announced a grand and joyous event.
Comets were generally regarded as malevolent harbingers: strange
apparitions whose appearance portended disaster. The sight of a comet
occasioned dread, not hope. Also, there is no record of a comet from
the time period of Jesus' birth, a range extending from 3 BC. to 1 AD.
*Perhaps the Star of Bethlehem was a Supernova?*
*"Supernova 1006'" This digitally enhanced photo by Tunc Tezel shows how
the supernova might have appeared in Earth's sky in 1006*
A supernova explosion occurs when a highly massive star explodes from the
inside out. These cataclysmic explosions literally destroy the star in a
blaze of glory. A supernova can produce as much energy as a galaxy and,
if close enough to Earth, will outshines all the stars and planets. When
Betelgeuse, Orion's eastern shoulder star, goes supernova, it will be
visible during the day and will cast a shadow on us at night! A supernova
could remain visible for a few months until it finally fades into
invisibility: plenty of time as to allow the Magi to make their pilgrimage
to Bethlehem.
A principal objection to this theory is that we have no record of such an
explosion having occurred between 3 BC and 1 AD or even within many years
before or after. Such a dramatic spectacle would have most assuredly come
to the attention of some sky watchers around the globe.
*Maybe Venus and Jupiter?*
Venus and Jupiter experienced a rare close conjunction in 2 BC, within the
time range of Jesus' birth. Venus and Jupiter are the two brightest
planets in our sky, with Venus being the far brighter of the two.
These two planets appeared to come so close to one another that Venus
actually occulted Jupiter: an immensely rare event, indeed. The
combination of these two planets could have produced a "star like object"
far brighter than any other single star!
The problem with this notion is in the timing and region of visibility.
The Venus-Jupiter occultation was not visible in the Middle East. (See
graphic below.) Such close planetary conjunctions, especially those
involving a rapidly moving inferior planet such as Venus, don't last long.
Venus and Jupiter wouldn't have stayed together for long. Also,
even if they were close enough to appear as single star, the resultant
light wouldn't have been as much of a spectacle as the previous paragraph
implies. Venus would have been more than seven times brighter than
Jupiter and would have merely have appeared to "swallow" its giant
planetary companion.
*The Venus-Jupiter occultation was only visible within the colored region
centered on South America. While Venus and Jupiter would have
appeared close together in Middle Eastern skies, the Magi would not have
witnessed the occultation. *
Consider this article to have been a humble confession of ignorance. We
don't know what the star of Bethlehem might have been. We don't even
know if it were a natural, as opposed to a supernatural, phenomenon.
(More things in Heaven and Earth, Horatio...) We do know that this
mysterious star will continue to exercise a fascination over astronomers
for many years to come, even though we all know that this persistent
question might ever find an answer.