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          * The Christmas Star *                By Patrick Moore
                                                Dec. 1989 Astronomy Now



   Whenever Venus  is  a  brilliant  evening  object  around  Christmas-  time,
astronomers  are  always  bombarded   with   one   particular  question:   "Can
Venus have been the Star of Bethlehem?  If  not,  what was that Star?"
   It is best to say, quite frankly,  that  we  do  not know what the  Star  of
Bethlehem was.  On the other hand, we  can  at   least  say  what  it  wasn't -
and there is no chance that Venus   could  have  been  the  cause.   The reason
is obvious  enough.   Venus  is  a  familiar  sight;   it  has been known since
the  dawn  of  human  history - and if the Wise Men could have been taken in by
Venus,  they would not have been very wise.
   The real problem is that our  information  is hopelessly scanty.   The  star
is  mentioned only once  in  the  Bible:   in   the   Gospel  according  to St.
Matthew, Chapter 2.  Matthew tells us that   the   Wise  Men from the East came
to Herod, saying "Where is  he  that   has  been  born King of the Jews? for we
have seen his star in  the  east,   and   are   come to worship him."  Verses 7
to  10  run  as  follows:

        "Then Herod, when he had privily called the wise men, inquired  of them
    diligently what time the star appeared.   And  he sent them  to  Bethlehem,
    and said, go and search  diligently  for   the   young  child;  and when ye
    have found him, bring me word  again,   that   I   may come and worship him
    also.
        "When  they  had heard the King,  they  departed;  and  lo,  the  star,
    which they saw on the east,  went  before  them,  till it  came  and  stood
    over where the young child was.  When   they  saw  the  star, they rejoiced
    with exceeding great joy."

   That  is all that St. Matthew tells  us; the other  Gospels  do  not mention
the star at all, and to make matters  worse we are  by  no  means certain about
our dates.  There  is  one   definite   fact:   Christ   was  not  born on 25th
December  A.D.  1.   Our   "A.D."   dates   are   reckoned   according  to  the
calculations of  the  Roman  monk  Dionysius  Exiguus, who died around the year
556.  He computed the  date   of   Christ's  birth  to  be 754 years after  the
founding  of  Rome,  and everyone since then has accepted his findings,  though
they  are certainly wrong.  Christ  was  born  before  A.D.  1.,  and  the most
likely date is B.C. 4, though with  a  possible  error of a  year or two either
way.  Moreover, 25 December was  not  celebrated   as  Christmas  Day until the
fourth century - by which  time  the   real date had long since been forgotten,
so that our Christmas is  wrong too.
   There  seems  no hope of finding any new evidence, and  so  we  must  simply
make do with what we have.  Venus  can   be  dismissed  out  of  hand.  So, for
that matter, can Mars,  Jupiter   and   all   other  planets and stars, because
they had already  been   charted   and   the   planetary  movements worked out.
If  Venus,  Mars  or  Jupiter had been particularly obtrusive, Herod would have
had  to  do  no  more   than   go   and   have   a  look.   For  a   scientific
explanation, we must cast around for something unusual.
   The old favourite, trotted  out  with  monotonous regularity,  is  planetary
conjunction.  When two planets pass close by  each other  the   effect  can  be
quite  spectacular,  and   there    can    be   occultations;   thus Saturn was
occulted by Mercury on 9  December   1808,   and  Jupiter by Venus on 3 January
1818.  The  next  mutual  occultations  will  be on 22nd November 2065 (Jupiter
occulted  by  Venus), 11 August 2079 (Mars by Mercury) and 27 October 2088  and
7 April 2094 (Jupiter by Mercury).
   There were various planetary  conjunctions  around  the   probably  time  of
Christ's birth.  The suggestion that this  may   be  the  origin of the Star of
Bethlehem story is old - it was proposed by  C. Pritchard as long ago as 1856 -
and it is worth discussing  in  more  detail here, because it has been recently
supported  by  Dr  David W. Hughes of the University of Sheffield.
   Of  the  planets, only three (Venus,  Jupiter  and Mars  at  its  infrequent
best)  are  markedly superior to any  of  the  stars.   Mercury we can discount
in this context; though its magnitude  may   surpass   that  of  Sirius, it can
never be seen  against  a  dark  background.   Saturn can attain magnitude -0.3
when it is at  its  most favourable  opposition with the rung-system wide open.
This  is rather brighter than Vega,  Capella  or even Alpha Centauri, but  well
below Sirius or Canopus.
   There  was  a  close  conjunction  of  Jupiter  and  Venus   in   1975,  and
certainly the view was impressive - but it was not of  brief  duration, and any
skilled star gazers, as the Wise Men  certainly  were, would have recognised it
for what it was.
   In  1987  there was a conjunction  of  Jupiter and  Mars,  which  again  was
quite impressive even though  Mars,   which   again  was  quite  impressive,was
only of magnitude 1.1  (rather  fainter   than   stars   such   as Aldebaran or
Antares).   It   may   be   significant,    however,   that  neither  of  these
conjunctions aroused much  interest   except   upon   the astronomically-minded
members  of  the  general  public.
   Hughes - and, before him,  in  1957,  the  German  writer Stauffe -  believe
that  the  Star  of   Bethlehem   was   due   to   a    triple  conjunction  of
Jupiter and Saturn in the year BC  7.   To  quote  Hughes'  paper  (Nature, vol
264, pp  513-7,  1976):  "All   in   all,   Jupiter  and  Saturn  have  orbital
periodicities of 12 and 29  years   respectively,  so Jupiter on average passes
Saturn every 20 years.   About  every  120 years, three successive conjunctions
take  place  over  about  6  months, this  being known as  a  triple  or  great
conjunction.  Such a conjunction will occur every  120 years and a  similar one
would have occurred in 7 BC.  On May 29,  September 29  and December 4, 7 BC, a
conjunction occurred in the constellation  of  Pisces,  which is astrologically
associated with  the  Jewish  people."   On  May   29 the two planets were less
than  1  degree  apart.
   THe  theory  sounds  attractive,  and  certainly   it  cannot  be  dismissed
out  of  hand, but it is fair  to  say  that  there  are  various objections to
it.  First, there is the  time  scale.   It  is   generally assumed by Biblical
experts that Christ was born around  the   year  BC 4.  Whether this is correct
or not is a  matter  for  debate;  on the whole it seems that BC 7, the year of
the  triple  conjunction,  may  be rather too  early, but it is  true  that  we
cannot be sure, because our whole  chronology  of this period is so  uncertain.
More  important  is  the   appearance   of   the   triple   conjunction itself.
Jupiter is brilliant, but no rival  Venus  and   as  we  have  seen, Saturn can
never become  much  brighter   than   magnitude  zero.   Though the two planets
would be prominent,  they  would   certainly  not  be startling; and again, the
Wise Men   would   have   known  about  the  conjunction,  on  the   reasonable
assumption  that they were astrologers.   And  thirdly, the triple  conjunction
was  a long-drawn out affair, extending  over  the  best part  of  a  year  all
told, whereas the Biblical inference is that it  was  a  one off phenomenon.
   With great respect to the eminent  astronomers  who support  the  theory,  I
must admit that I have not the  slightest  faith in  it,  because  it  falls on
almost every count.  Even  before  our  own   time,  it was proposed by no less
a person that  Johanne  Kepler,  and   no  doubt  it  will be revived again and
again in the years   to   come,  but  I  am  bound  to  agree  with the opinion
expressed in  1908  by  E.W.   Maunder   in  his classic book   'The  Astronomy
Of  The  Bible':  "A   similar   and  closer  conjunction   occurred  59  years
earlier, and should therefore have brought a Magian deputation to  Judea  then.
Next, that the two planets never   approached   each  other  nearer  than twice
the apparent diameter of the  Moon,   so   that  they  would  have appeared not
as one star  but  two.   And  thirdly, if  the planets had seemed to stand over
Bethlehem as the  Wise  Men  left   Jerusalem,  they would most  assuredly  not
have  appeared  to   do   so   when   they   arrived   at   the   little  city.
Ingenious as the suggestion was, it may  be dismissed as  unworthy  of  serious
consideration.  The next candidate is our  old  friend  Halley's  Comet,  which
has been so much to the  fore  in  recent  years.   It  returns  every 76 years
(give or take  a  few  years  either way), and it can be brilliant, despite its
poor showing in  1985-6.    Halley's  Comet  came  to  perihelion  in BC 12, on
October  10,  and was observed  from  26th  October  of  that year, but we  can
certainly  rule  it out.  For one  thing, it was  reasonably  well  documented.
Secondly,  it  was too early.   Christ  was  almost  certainly born well before
BC 12.
   It  must be conceded that our records of other  comets  around  that  period
are not complete, and there may have been  a  bright  one in BC 5.  Even within
the past century or two there have been  comets  brilliant enough to be seen in
broad daylight,  and  some   have   even  cast  shadows,  though they have been
depressingly  rare  in  recent  times;  nobody  can  remember  a comet to rival
those  of,  say  1811, 1843, 1861,  or  1882.  But the same  objections  apply,
and the fragmentary  description  we  have  of  the  star  of  Bethlehem  lends
absolutely no support to the idea that it could have been a  comet.

   What, then, about a nova  or  supernova?   Initially this  sounds  much more
promising, and we know that several  galactic  supernova  have  been  seen over
the past thousand years.  The   outburst   of   1054,   which has left the crab
nebula became bright enough  to   be   visible  in  broad  daylight; so did the
supernova of 1572  (Tycho's   Star)   and  that  of  1604 (Kepler's Star).  All
these seem to   have   been   outshone  by  the  admittedly fragmentary reports
which  have  come  down to us, the  Lupus Star may have rivalled  the  quarter-
moon.   On those grounds, a  supernova  would  be  a  good  candidate  for  the
Star of Bethlehem, but there  are  two   fatal   objections.   First,  it would
have persisted for along time - weeks at  least,  more probably months.  And of
course, it would have been reported  by  contemporary  astronomers, but nothing
of the sort  has  come   down  to  us.   Moreover,  it  would have been plainly
visible at  the  time when the Wise Men were in Jerusalem.
   An  ordinary nova might fill the  bill,  because the  period  of  visibility
would possibly have been briefer; remember  the  last  bright  nova, in Cygnus,
which rocketed to the  first  magnitude,  but  within a week had faded to below
naked-eye visibility.   Yet  surely   it  would  have been mentioned elsewhere,
and as  with  our  other candidates, the contemporary records are silent.
   Planets, comets, nova and supernova have  failed  us; so what is  left?   If
we  are looking for something  which   moves,   I   think  instinctively  of an
aurora, but aurora are very seldom  seen   in   latitudes  as low as as that of
Jerusalem (though, admittedly,  an   aurora  was  once recorded from Singapore,
only about a degree from   the   equator).    But  in this case the description
given  by  St.  Matthew  would   have   been   hopelessly   wrong,  and  it  is
very  difficult   to   believe  that  an  auroral  display   could   have  been
involved.
   About 30 years ago, in a television Sky At Night programme,  I  put  forward
another idea, though I cannot claim  to   have  much  confidence  it  it.   Can
St. Matthew's  report  relate  to  two  meteors?
   If  the  Wise  Men   saw   one   brilliant  fireball   travelling  eastward,
they might well take it  as  some  sort  of  sign;   and  if  another  fireball
followed later, taking much the  same   course,   they  could have regarded the
miracle as confirmed.   This  would  explain  the eastward motion, and also why
only the Wise Men  saw  the phenomenon at all.
   I  doubt  whether many people will  take this  explanation  any  better than
I do, but - well, what  else  can  one  say?   The chances  of  finding any new
evidence seem to be effectively  nil.    Until   the  end of time, that Star of
Bethlehem will remain a fascinating  enigma.


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