Afterthought (January 16th 2018):
One note to add that bears remembering.
As was pointed out in post #9, we know that Chinese records from the period between 20 BC and 1 AD are almost certainly incomplete. In this twenty year period there are just four records. If we follow the conventional reasoning, two of these four events appear to be clerical errors – often called “ghost events” for which an error in the date written when copying an old record created a second entry for the same event.
So, the two records in 12 BC and 10 BC are both of Comet Halley’s 12 BC return. And the records in 5 BC and 4 BC appear to be of the same object that appeared in Southern Aquila or Northern Capricorn in late March 5 BC (given that, at the end of March 5 BC the Last Quarter Moon would have been very close to the position given by the Chinese records, it is reasonable that the less sophisticated Korean astronomers would give a reference position close to the brightest star that they could actually see in that area of the sky).
However, over two decades, we would expect to see around six to seven naked-eye comets, of which typically two would get to magnitude zero or brighter, plus one to two bright novae. In other words, where we expect from seven to nine records statistically (assuming that the last century or so has been typical for the appearance of bright comets and bright novae), we find just two.
The Chinese seem to have been particularly bad at recording novae, or Guest Stars. Their name for them was Ko-hsing, but very few good candidate novae were recorded by the Chinese and, of the best candidates (long duration objects with no movement recorded), a third are actually supernovae, suggesting that an object had to be extremely bright to get their attention. They were also inconsistent in using the name Ko-hsing, with Hui-hsing and Po-hsing (both “comet”) often being used for very bright objects (below).
This leads to two options that are both viable:
- The 5 BC star was a very bright nova – almost certainly negative magnitude – and that the classical image of the Magi following an overwhelmingly bright star is a good representation of how they would have seen it. Or,
- The Star was another bright object that simply did not make it into the surviving Chinese records.
If the correct answer is #1, there is no issue: there was an extremely bright star that appeared suddenly in the eastern sky in the second half of March 5 BC, about a year before the unlamented death of King Herod. You can call it Nova Bethlehem, if you wish.
If the correct answer is #2, we may never know what the Star of Bethlehem was really because there are, we believe, no more records to find and translate. We have all the oriental records, we have the Babylonian records, we have the Roman records: there are no more big potential datasets to find that might reveal more observations from this epoch.